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Ethyl Carbamate (Urethane) in the Treatment of Chronic Myelocytic Leukemia: Results of a Three-Year Study
ETHYL CARBAMATE (URETHANE) IN THE TREATMENT OF CHRONIC MYELOCYTIC LEUKEMIA Results of a Three-Year Study TALBERT COOPER AND CHARLES
H.
WATKINS
Urethane, the ethyl ester of carbamic acid, has been employed in the symptomatic treatment of bronchial asthma,5 as a mild hypnotic, as an anesthetic for laboratory animals, and more prosaically, in combination· with quinine hydrochloride as a sclerosing solution for the injection treatment of varicose veins. 7 Its demonstrated pharmacologic and physiologic activities include an inhibitory effect on the usual response of sensitized plain muscle in guinea pigs;5 in low concentrations, an antisulfonamide action in the presence of certain luminous bacteria, similar to that of para-aminobenzoic acid ;15 in 2 to 3 per cent solution, a bacteriostatic capacity involving a wide range of organisms ;23, 24 the depression of the respiratory rate of yeasts ;23, 24 and, toxic effects on paramecium, developing eggs of marine animals, and fibroblasts in tissue culture. 6 Guyer and Claus observed that the mitotic activity of corneal epithelium of rats and mice was markedly inhibited for periods of eight to twelve hours after the intraperitoneal injection of urethane. Lefevre produced monstrous cytologic alterations in grain seedlings throug,h' the action of ethyl phenyl carbamate. These he regarded as the result of blocking of mitosis in pseudometaphases. The biologic activity of the urethanes has been reasonably attributed to an inhibition of essential cellular enzyme systems but the precise mode of action remains speculative. Haddow and Sexton observed retardation of growth and alteration of histologic structure of Walter rat carcinoma following administration of urethanes. Edith Paterson found the substances of limited value in the treatment of metastatic carcinoma of human beings but noted the consistent development of leukopenia in those so treated. In 1946 Paterson and co-workers reported encouraging early results in patients having chronic leukemia who were given urethanes, principally ethyl carbamate, orally. The results compared favorably with those usually observed after the therapeutic administration of roentgen irradiation in similar cases. Rather numerous confirmatory reports were published thereafter,l, 12,21 adding to the enthusiastic hopefulness in regard to the chemotherapy of the leukemias and related diseases previously stimulated by the introduction of the nitrogen mustards. 1205
1206
TALBERT COOPER, CHARLES H. WATKINS
It was soon apparent, however, that even the palliative usefulness of ethyl carbamate was decidedly limited. The course of acute leukemia was not significantly altered. Chronic lymphocytic leukemia responded inconsistently and chronic monocytic leukemia was rarely favorably influenced.!' 12,20,21 In chronic myelocytic leukemia, however, the early clinical and hematologic results of treatment were generally regarded as encouraging. It was hoped that the obvious advantage of oral administration together with the potentially greater effectiveness resulting from continuous long-term action of the drug might establish treatment with ethyl carbamate as more effective than treatment with other .commonly employed palliative agents. Early experience with the use of urethane at the Mayo Clinic clearly indicated its relatively greater and more consistent effectiveness in cases of chronic myelocytic leukemia than in other types of leukemia and its recent application in our hands has been limited to cases of leukemia of this type. In occasional cases of multiple myeloma an encouraging response to treatment with urethane has been obtained but discussion of these cases is beyond the scope of this paper. During the past three years we have employed urethane in the treatment of 42 patients having chronic myelocytic leukemia. The period of observation is now sufficient to permit further evaluation of the results of therapy in this group of patients. SELECTION OF CASES
The diagnosis of chronic myelocytic leukemia was based on clinical as well as hematologic features in each case. Every effort was made to exclude instances of acute or subacute leukemia from the group under consideration. Five of the 42 cases were discarded from our study of results of treatment because treatment with urethane was not carried out in these cases for a period sufficient to permit their inclusion in an analysis of the long-term results of treatment with this agent. In 2 of these 5 eases treatment with urethane was instituted one and three days respectively before death from terminal leukemia. In 3 cases it became necessary to discontinue treatment because intractable nausea and vomiting developed. These patients received the drug for periods of two, seven and twelve days respectively. The remaining 37 patients were divided into two approximately equal groups on the basis of the duration of signs or symptoms referable to chronic leukemia ·prior to institution of treatment with urethane. It is recognized that the rapidity of progress of the disease often varies markedly among patients originally presenting superficially similar clinical and hematologic features. However, the separation of our cases
URETHANE IN CHRONIC MYEI~OCYTIC LEUKEMIA
1207
into an early group, that is, cases in which signs and symptoms referable to chronic myelocytic leukemia had been present less than nine months and a moderately advanced group makes easier the appraisal of the influence of urethane therapy under the circumstances of this study. The early group included many previously untreated patients together with others on whom other modes of treatment, particularly the administration of ionizing irradiation had fairly consistently produced temporary remissions; in the moderately advanced group other measures had often become ineffective, and the production of favorable results by a new agent would have added significance. The early group consisted of 20 patients, 9 women and 11 men, in whom manifestations of the disease had been present for an average of 4.8 months. These patients ranged in age from 21 to 59 years, the average age being 41 year.s. Fourteen patients had not received any specific treatment previously. The remaining 6 had received minimal roentgen therapy. All were in a state of clinical or hematologic relapse or both at the time treatment with urethane was instituted. The moderately advanced group of 17 cases included 11 females and 6 males. The age of patients in this group ranged from 15 to 56 years with an average of 38 years. Manifestations of the leukemic process had been present from nine to seventy-two months, the average apparent duration of the disease being twenty-three months. With two exceptions, all members of this group had previously been treated repeatedly with roentgen irradiation, radioactive phosphorus, or Fowler's solution. Fourteen patients were regarded as relatively refractory to the effects of ionizing radiation. Treatment with urethane alone has now been carried out in these cases for periods ranging from five weeks to twenty-nine months. DOSAGE
As previously stated it became necessary to discontinue treatment within twelve days in 3 patients because of the development of intractable nausea and vomiting. The dosage prescribed in these cases ranged from 3 to 6 gm. daily. As a result of this early experience progressively smaller amounts were administered daily in subsequent cases until it became apparent that equally satisfactory early results could be accomplished in most instances by administration of 0.5 gm. of urethane three times a day. Thereafter the inciden'ce of distressing gastro-intestinal symptoms was considerably reduced. Patients who failed to respond to urethane in a dosage of 1.5 gm. daily rarely responded to larger amounts. The total amount of urethane necessary to produce objective evidence of hematologic and clinical effectiveness was variable. Significant reduction in the total leukocyte count in patients responding favorably
1208
TALBERT COOPER, CHARLES H. WATKINS
usually occurred within two to four weeks after the institution of treatment. Encouraging hematologic remissions were consistently followed by a I evidences of relapse in three to eight weeks after treatment was discontinued. Further, a urethane-refractory state rather commonly appeared in cases in which the response to treatment ,vas encouraging at first. This state seemed particularly likely to develop if treatment was completely suspended for a time and subsequently resumed. Some advantage appeared to re~ult from the continuous administration of small amounts of urethane even after remission was well established in an effort to prevent the development of a refractory state. TABLE RESULTS OF URETHANE THERAPY IN
1
20
CASES OF EARLY CHRONIC
MYELOCYTIC LEUKEMIA
Duration of Urethane Therapy, mo.
Results Subsequent I~,oentgen
Therapy
1-6
6-12
12-18
18-24
--
Satisfactory clinical and hematologic remission Satisfactory early remission: later refractory No appreciable effect on clinical course
o Patient living . • Patient dead.
0
0 0
o.
o.
••• ••
24-30 ---
0 ••
0
o.
0
0
Good
Poor
~ - _ . -
0 000
• ••
0
RESULTS OF TREATMENT
The response of patients in this series to the administration of urethane followed one of three general courses: 1. A satisfactory clinical and hematologic remission of the disease resulted and was sustained. The character of the remissions observed approximated those resulting from irradiation therapy with the usual decrease in the number of leukocytes in the peripheral.blood, a marked reduction in the percentage of abnormal immature cells in the peripheral blood and bone marrow, partial to complete relief of anemia when present, and reduction in the size of the spleen. 2. A satisfactory cliIiicaland hematologic remission ensued, but was succeeded, despite the continued administration of urethane, by relapse. A urethane-refractory state appeared to develop in such patients. 3. The progress of the disease was not appreciably influenced
URETHANE IN CHRONIC MYELOCy'rIC LEUKEMIA
1209
although in the majority of patients in this group temporary reductions in the total leukocyte count were observed. The results of treatment in the early and moderately advanced groups of patients are summarized in tables 1 and 2. The duration of treatment with urethane in each case also is indicated. In cases in which roentgen irradiation was subsequently employed under our supervision the results are tabulated. The Early Group. Satisfactory clinical and hematologic remissions were produced and sustained in 3 cases. In 1 patient treatment with urethane was discontinued after eight months because of the development of muscular aching, stiffness and headache. These symptoms TABLE 2 RESULTS OF URETHANE IN
17
CASES OF MODERATELY ADVANCED CHRONIC
MYELOCYTIC LEUKEMIA
Duration of Urethane Therapy, mo. 1-6
Satisfactory clinical and hematologic remission Satisfactory early remission: later refractory No appreciable effect on clinical course
o
•
6-12
12-18
18-24
Results Subsequent Roentgen Therapy Good
Poor
o 00. • • • • •• • ••
••
•
o
00
•• • ••
•
Patient living. Patient dead.
rapidly disappeared when administration of urethane was suspended and this patient's subsequent response to roentgen irradiation was satisfactory. Treatment of the other 2 patients has been continued for periods of nineteen and twenty-nine months respectively with relatively complete suppression of clinical and hematologic evidences of leukemia and with freedom from unpleasant toxic effects attributable to the drug. In 7 patients a definite remission lasting from two to sixteen months (average 10.2 months) was effected; however, resistance to this type of therapy: eventually developed and could not be overcome by increased dosage or pro~onged continuation of treatment. In 3 instances roentgen irradiation was then administered under our supervision with satisfactory results; an additional patient responded satisfactorily to similar treatment administered elsewhere. In the 3 remaining cases the disease progressed rapidly' to termination in an acute leukemic phase.
1210
TALBERT COOPER, CHARLES H. WATKINS
Of the 10 patients in this group who derived no apparent benefit from the action of urethane 7 have died. Five of the 10 patients had an encouraging early fall in the total leukocyte count but, in all other respects, the course of the disease was not measurably influenced by urethane. Roentgen irradiation which was administered after treatment with urethane in 4 cases was similarly ineffective. The Moderately Advanced Group. The single satisfactory remission achieved in this group has now been sustained for twenty-two months, during which time the patient has had a normal pregnancy and was delivered of a normal infant. Prior to the use of urethane satisfactory remissions had been produced in this case by a course of roentgen irradiation and two courses of treatment with radioactive phosphorus. She has now survived for approximately five years since the onset of symptoms. In 6 cases satisfactory early responses were followed within four to fourteen months (average 9 months) by the development of urethane refractory states. Thereafter the disease progressed rapidly to fatal termination in 3 cases, the course not being favorably influenced by roentgen therapy which was carried out in 2. However, 2 other patients in this group responded satisfactorily to the subsequent administration of roentgen irradiation. Urethane therapy produced no significant change in the course of the 10 remaining patients although in 9 patients of this group a temporary reduction of the total leukocyte count was effected. All cases terminated fatally three to sixteen months ·after the institution of therapy with urethane. Roentgen irradiation which was' also employed in 4 cases was similarly futile. GENERAL OBSERVATIONS
While, generally speaking, the response to treatment with urethane was more encouraging in the relatively early condition as might have been anticipated, it seems more significant that 10 of the 20 cases in this group were not measurably affected by the treatment. As is true of the response to most palliative agents currently employed, a poor response to urethane therapy appears to suggest a relatively poor prognosis (table 3). Exceptions occurred but patients presenting more marked degrees of splenomegaly responded less favorably to treatment. Although the enlargement of the spleen was often considerably reduced by urethane therapy; the degree of shrinkage was usually less marked than that commonly accomplished by irradiation therapy under similar circumstances. Previous therapeutic irradiation appeared to hav.e no specific effect on a patient's capacity to respond to urethane therapy. However, in
1211
URETHANE IN CHRONIC MYELOCYTIC LEUKEMIA
no instance were significantly beneficial effects obtained with urethane in cases in which irradiation-refractory states were present. The reverse was true with certain reservations. Patients for whom the use of urethane appeared entirely futile responded poorly when irradiation therapy was subsequently employed. However, many patients whose condition became resistant to the effects of urethane after initial satisfactory remissions had been produced with this treatment subsequently responded satisfactorily to roentgen irradiation. It is interesting, although in this small group of patients of no necessary significance, that the 3 patients continuing with urethane therapy after remissions of eighteen months or more are females-aged 26, 43 and 48 years. Two thirds of a group of patients surviving for periods of more TABLE 3 CHARACTER OF RESPONSE TO URETHANE AS A PROGNOSTIC INDICATOR
Response Satisfactory clinical and hematologic remission Satisfactory early remission: later refractory No appreciable effect on clinical course Total
Patients Total
Dead
4
13
6
20
17
37
23
than five years from the date of diagnosis of chronic myelocytic leukemia which were reviewed by Moffitt and Lawrence were women. The total leukocyte count of the peripheral blood together with the percentage of abnormal immature cells in the peripheral blood and bone marrow was reduced in some cases in which there was no other significant evidence of a favorable response. Berman and Axelrod observed similar results in cases in which on postmortem examination histologically undisturbed leukemic infiltrations were noted in the liver despite previous marked reduction in the number of leukocytes in the circulating blood. Twenty-three of the 37 patients receiving urethane therapy during the past three years are dead. Nine of these came under our observation during the terminal stages of their illnesses and 8 presented the features of acute transition of the leukemic process. Whether the action of urethane contributed to this change cannot be determined. Jaffe demonstrated the development of pulmonary adenomas and .hepatomas in mice receiving injections of urethane. A high incidence of terminal
1212
TALBERT COOPER, CHARLES H. WATKINS
acute leukemia also has been observed in cases of chronic leukemia treated with radioactive phosphorus.l° It may well be that the widespread use of blood transfusions and antibiotic substances has resulted in control of the effects of chronic anemia and intercurrent infections to the extent that the majority of aggressively treated patients will continue to succumb as the result of an acute transition of the process regardless of the palliative agent employed. ' In the 23 cases which have terminated fatally, the average duration of life from the onset of symptoms to death was twenty-seven months. Patients in our group who have survived thus far have had evidence of the disease for an average period of thirty months. It seems doubtful that the average duration of life for the entire group will be significantly prolonged. TOXICITY
Undesirable side .effects were commonly encountered but the degree of resultant subjective distress was usually directly proportional to the dosage employed and became tolerable when the dosage was reduced. Nausea, vomiting and other symptoms of gastro-intestinal irritation including so-called gas pains and diarrhea occurred at some time in the course of treatment in approximately 60 per cent of the patients. In only 3 instances, however, was it necessary to discontinue treatment on this account. Neither intravenous nor rectal routes of administration, which might mitigate the gastro-intestinal disturbances to a considerable degree, were employed in these cases. In addition to symptoms referable to the gastro-intestinal tract, patients complained of lethargy, loss of "pep," feeling "half sick all the time," dizziness, muscular aching, muscular stiffness and headache. ,:On some occasions it was felt that the underlying disease contributed to these difficulties but most patients were much improved subjectively in so far as these rather vague complaints were concerned when the amount of urethane administered was markedly reduced or this treatment was discontinued entirely. Serious depression of hematopoiesis was not observed in this series and rare difficulties of this sort have been reported by others employing the materia1. 20 • 22 Although the production of renal glomerular lesions and hepatic venocapillary injury in mice and rats treated with urethane has been reported,4. 16 there was no evidence of such damage resulting from treatment in this series. In Huggins' case of toxic hepatitis, which developed after the treatment of metastatic carcinoma of the prostate with urethane, the dosage employed was 9 gm. daily for thirty-three days.
URErl'HANE IN CHRONIC MYELOCyrrIC LEUKl!}MIA
1213
COMMENT
The results of this study indicate that the use of urethane contributes little to the palliative treatment of patients with chronic myelocytic leukemia. The practical advantage of an agent which may be administered orally seems clearly outweighed by its general ineffectiveness and the bothersome side effects resulting from its administration. Roentgen therapy, which may be expected to produce satisfactory temporary palliation of symptoms in 90 per cent of cases of this type, remains the most consistently effective mode of treatment generally available at present. Although roentgen therapy often resulted in satisfactory remissions after the development of urethane refractory states in cases in the series, urethane therapy contributed nothing to the patient whose condition had become resistant to the effects of ionizing radiation. We have employed small doses of urethane in several cases of chronic myelocytic leukemia in which roentgen therapy was being given periodically in an effort to prolong the roentgen-induced remission. Ilesults thus far have been inconclusive but do not appear to justify the general adoption of this combination of therapeutic agents. Urethane, however, represents an addition to the rather large body of agents having some demonstrable, if not therapeutically important, effect on leukemic processes. While the action of urethane has been attributed to its capacity for direct action on cellular metabolic activity, most apparent on actively dividing cells, it may well be that its modus operandi is indirect and that the other various factors including intercurrent infections, which may produce temporary remissions in patients with leukemia act through a common pathway. Fragmentary evidence is available to suggest that urethane may produce adrenal cortical stimulation. Hawkins and Murphy found that in rabbits or rats anesthetized with urethane the carbon dioxide combining power and pH of the whole blood are increased to the point of marked uncompensated alkalosis, which reaches a maximum twenty-four hours after anesthetization and persists for forty-eight hours. This alkalosis is accompanied by a decrease in number of circulating lymphocytes and an increase in polymorphonuclear neutrophils. Irradiation of the animals provoked similar changes as did the intravenous injection of sodium bicarbonate. Boyd and Perry found the potassium content of bronchial secretions two to four times higher in cats under urethane anesthesia than in decerebrate cats. At the same time the average concentration of serum potassium was reduced from 21.5 to 17.8 mg. per 100 cc. Kirschbaum and I-Ju, however, have been able to obtain the usual "urethane effect" in adrenalectomized leukemic mice.
1214
'rALHER1' COOPER, CHAHLES H. WA'rKINS
SUMMARY
Satisfactory sustained remissions were achieved in 4 of 37 cases of chronic myelocytic leukemia in which ethyl carbamate (urethane) was administered. In an additional 13 cases significant early remissions were followed by the development of a urethane-refractory state and the appearance of clinical and hematologic relapse. In the remaining 20 cases treatment with ethyl carbamate was not clinically effective although in 14 cases a moderate reduction in the total leukocyte count of the peripheral blood was effected. The administration of therapeutically active amounts of urethane resulted in distressing side effects in many instances although no serious side effects were observed. Ionizing roentgen radiation is much more consistently effective in the palliative treatment of chronic myelocytic leukemia than is urethane. REFERENCES 1. Bedinger, P. L., Poncher, H. G. and Limarzi, L. R.: F~ffect of Urethane on Leucemia. J. Lab. & Clin. Med. 32 (pt. 2): 1394-1395,1947. 2. Berman, Lawrence and Axelrod, A. R.: Effect of Urethane on Malignant Diseases; Clinical, Hematologic and Histologic Observations on Patients With Carcinoma, Leukemia and Related Diseases. Am. J. Clin. Path. 18: 104-129 (Feb.) 1948. 3. Boyd, E. M. and Perry, W. F.: Urethane Administration and Potassium Content of Bronchial Secretions in the Cat. Proc. Soc. Exper. BioI. & Med. 57: 334-335 (Dec.) 1944. 4. Doljanski, L. and Rosin, A.: Studies on the Early Changes in the Livers of Rats Treated With Various Toxic Agents, With Especial Reference to the Vascular Lesions. 1. The Histology of the Rat's Liver in Urethane Poisoning. Am. J. Path. 20: 945-960 (Sept.) 1944. 5. Farmer, Laurence: The Use of Urethane in Symptomatic Treatment of Bronchial Asthma. J. Lab. & Clin. Med. 24: 453-454 (Feb.) 1939. 6. Geiersbach, Ute: TIber den Einfluss del' N arkose (Urethan) auf Gewebekulturen. Arch. f. expel'. Zellforsch. 23: 210-219, 1939. 7. Goodman, L. S. and Gilman, Alfred: The Pharmacological Basis of Therapeutics; a Textbook of Pharmacology, Toxicology and Therapeutics for Physicians and Medical Students. New York, The Macmillan Company, 1941, 1383 pp. 8. Guyer, M. F. and Claus, P. E.: Effects of Urethane (Ethyl Carbamate)on Mitosis. Proc. Soc. Expel'. BioI. & Med. 64: 3-5 (Jan.) 1947. 9. Haddow, Alexander and Sexton, W. A.: Influence of Carbamic Esters (Urethanes) on Experimental Animal Tumours. Nature, London. 157: 500-503 (Apr. 20) 1946. 10. Hall, B. E. and Watkins, C. H.: Radiophosphorus in the Treatment of Blood Dyscrasias. M. CLIN. NORTH AMERICA. 31: 810-840 (July) 1947. 11. Hawkins, J. A. and Murphy, J. B.: The Effect of Ethyl Urethane Anesthesia on the Acid-base Equilibrium and Cell Contents of the Blood. J.Exper. Med. 42: 609-618 (Nov. 1) 1925. 12. Hirschboeck, J. S., Lindert, M. C. F., Chase, Jules and Calvy, T. L.: Effects of Urethane in the Treatment of Leukemia 'and Metastatic Malignant Tumors. J.A.M.A. 136: 90-94 (Jan. 10) 1948. 13. Huggins, Charles, Yu, S. T. and Jones, Ralph, Jr.: Inhibitory Effects of Ethyl Carbamate on Prostatic Cancer. Science. n.s. 106: 147-148 (Aug. 15) 1947.
URETHANE IN CHRONIC MY:bJI--IOCYTIC LEUKEMIA
1215
14. Jaffe, Rudolf: flistological Findinga in Lungs and Livers of Rats Treated With Ethyl Urethane. Cancer Research. 7: 111-112 (Feb.) 1947. 15. Johnson, F. H.: Mechanism of P-aminobenzoic Acid Action and the Parallel F~ffects of Ethyl Carbamate (Urethane). Science. n.s. 95: 104-105 (Jan. 23) 1942. 16. Kirschbaum, ~Arthur and Bell, E. T.: Induction of Renal Glomerular Lesions by Urethane in Inbred Mice Susceptible to Spontaneous Glomerulonephritis. Proc. Soc. Expel'. BioI. & Med. 64: 71-72 (Jan.) 1947. 17. Kirschbaum, Arthur and Lu, C. S.: Effect of Urethane on Normal and Leukemic Hemopoietic Tissues of the Mouse. Unio Internationalis Contra Cancrum. Aeta. 6: 530-533, 1949. 18. Lefebvre, Joseph: Similitude des actions cytologiques exercees par Ie phenylurethane et la colchicine sur des plantules vegetales. Compt. rend. Acad. d. sc. 208: 301-304 (Jan. 23) 1939. 19. Moffitt, H. C., Jr. and LaNrence, J. H.: Chronic Leukemia of Long Duration: With a Report of 31 Cases With a Duration of Over Five Years. Ann. Int. Med. 30: 778-790 (Apr.) 1949. 20. Paterson, Edith, Haddow, Alexander, Ap Thomas, Inez and Watkinson, Jean M.: Leukemia Treated With Urethane; Compared With Deep X-ray Therapy. Lancet. 1: 677-682 (May 11) 1946. 21. Watkins, C. H. i Cooper, Talbert and Giffin, H. Z.: The Use of Urethane (Ethyl Carbamate) in the Treatment of Leukemia; a Preliminary Report. Blood. 3: 892-895 (Aug.) 1948. 22. Webster, J. J.: Urethane in Leukemia. J.A.M.A. 135: 901-903 (Dec. 6) 1947. 23. Weinstein, Louis and McDonald, Alice: 'Tlhe Action of Urea and SOIne of Its Derivatives on Bacteria. 1. Bacteriostatic and Bactericidal Effects of Urea and Urethane ..J. Immunol. 54: 117-130 (Oct.) 1946. 24:. Weinstein, I.Jouis and McDonald, Alice: The Action of Urea and Some of Its Derivatives on Bacteria. II. The A.ntibacterial Activity of Combinations of Urea and Urethane With Sulfonamides and the Effect of the Carbamates on Para-aminobenzoic Acid and on the Solubility of SulfonaInide3. J. Immunol. 54: 131-144 (Oct.) 1946.
H.
WATKINS
Urethane, the ethyl ester of carbamic acid, has been employed in the symptomatic treatment of bronchial asthma,5 as a mild hypnotic, as an anesthetic for laboratory animals, and more prosaically, in combination· with quinine hydrochloride as a sclerosing solution for the injection treatment of varicose veins. 7 Its demonstrated pharmacologic and physiologic activities include an inhibitory effect on the usual response of sensitized plain muscle in guinea pigs;5 in low concentrations, an antisulfonamide action in the presence of certain luminous bacteria, similar to that of para-aminobenzoic acid ;15 in 2 to 3 per cent solution, a bacteriostatic capacity involving a wide range of organisms ;23, 24 the depression of the respiratory rate of yeasts ;23, 24 and, toxic effects on paramecium, developing eggs of marine animals, and fibroblasts in tissue culture. 6 Guyer and Claus observed that the mitotic activity of corneal epithelium of rats and mice was markedly inhibited for periods of eight to twelve hours after the intraperitoneal injection of urethane. Lefevre produced monstrous cytologic alterations in grain seedlings throug,h' the action of ethyl phenyl carbamate. These he regarded as the result of blocking of mitosis in pseudometaphases. The biologic activity of the urethanes has been reasonably attributed to an inhibition of essential cellular enzyme systems but the precise mode of action remains speculative. Haddow and Sexton observed retardation of growth and alteration of histologic structure of Walter rat carcinoma following administration of urethanes. Edith Paterson found the substances of limited value in the treatment of metastatic carcinoma of human beings but noted the consistent development of leukopenia in those so treated. In 1946 Paterson and co-workers reported encouraging early results in patients having chronic leukemia who were given urethanes, principally ethyl carbamate, orally. The results compared favorably with those usually observed after the therapeutic administration of roentgen irradiation in similar cases. Rather numerous confirmatory reports were published thereafter,l, 12,21 adding to the enthusiastic hopefulness in regard to the chemotherapy of the leukemias and related diseases previously stimulated by the introduction of the nitrogen mustards. 1205
1206
TALBERT COOPER, CHARLES H. WATKINS
It was soon apparent, however, that even the palliative usefulness of ethyl carbamate was decidedly limited. The course of acute leukemia was not significantly altered. Chronic lymphocytic leukemia responded inconsistently and chronic monocytic leukemia was rarely favorably influenced.!' 12,20,21 In chronic myelocytic leukemia, however, the early clinical and hematologic results of treatment were generally regarded as encouraging. It was hoped that the obvious advantage of oral administration together with the potentially greater effectiveness resulting from continuous long-term action of the drug might establish treatment with ethyl carbamate as more effective than treatment with other .commonly employed palliative agents. Early experience with the use of urethane at the Mayo Clinic clearly indicated its relatively greater and more consistent effectiveness in cases of chronic myelocytic leukemia than in other types of leukemia and its recent application in our hands has been limited to cases of leukemia of this type. In occasional cases of multiple myeloma an encouraging response to treatment with urethane has been obtained but discussion of these cases is beyond the scope of this paper. During the past three years we have employed urethane in the treatment of 42 patients having chronic myelocytic leukemia. The period of observation is now sufficient to permit further evaluation of the results of therapy in this group of patients. SELECTION OF CASES
The diagnosis of chronic myelocytic leukemia was based on clinical as well as hematologic features in each case. Every effort was made to exclude instances of acute or subacute leukemia from the group under consideration. Five of the 42 cases were discarded from our study of results of treatment because treatment with urethane was not carried out in these cases for a period sufficient to permit their inclusion in an analysis of the long-term results of treatment with this agent. In 2 of these 5 eases treatment with urethane was instituted one and three days respectively before death from terminal leukemia. In 3 cases it became necessary to discontinue treatment because intractable nausea and vomiting developed. These patients received the drug for periods of two, seven and twelve days respectively. The remaining 37 patients were divided into two approximately equal groups on the basis of the duration of signs or symptoms referable to chronic leukemia ·prior to institution of treatment with urethane. It is recognized that the rapidity of progress of the disease often varies markedly among patients originally presenting superficially similar clinical and hematologic features. However, the separation of our cases
URETHANE IN CHRONIC MYEI~OCYTIC LEUKEMIA
1207
into an early group, that is, cases in which signs and symptoms referable to chronic myelocytic leukemia had been present less than nine months and a moderately advanced group makes easier the appraisal of the influence of urethane therapy under the circumstances of this study. The early group included many previously untreated patients together with others on whom other modes of treatment, particularly the administration of ionizing irradiation had fairly consistently produced temporary remissions; in the moderately advanced group other measures had often become ineffective, and the production of favorable results by a new agent would have added significance. The early group consisted of 20 patients, 9 women and 11 men, in whom manifestations of the disease had been present for an average of 4.8 months. These patients ranged in age from 21 to 59 years, the average age being 41 year.s. Fourteen patients had not received any specific treatment previously. The remaining 6 had received minimal roentgen therapy. All were in a state of clinical or hematologic relapse or both at the time treatment with urethane was instituted. The moderately advanced group of 17 cases included 11 females and 6 males. The age of patients in this group ranged from 15 to 56 years with an average of 38 years. Manifestations of the leukemic process had been present from nine to seventy-two months, the average apparent duration of the disease being twenty-three months. With two exceptions, all members of this group had previously been treated repeatedly with roentgen irradiation, radioactive phosphorus, or Fowler's solution. Fourteen patients were regarded as relatively refractory to the effects of ionizing radiation. Treatment with urethane alone has now been carried out in these cases for periods ranging from five weeks to twenty-nine months. DOSAGE
As previously stated it became necessary to discontinue treatment within twelve days in 3 patients because of the development of intractable nausea and vomiting. The dosage prescribed in these cases ranged from 3 to 6 gm. daily. As a result of this early experience progressively smaller amounts were administered daily in subsequent cases until it became apparent that equally satisfactory early results could be accomplished in most instances by administration of 0.5 gm. of urethane three times a day. Thereafter the inciden'ce of distressing gastro-intestinal symptoms was considerably reduced. Patients who failed to respond to urethane in a dosage of 1.5 gm. daily rarely responded to larger amounts. The total amount of urethane necessary to produce objective evidence of hematologic and clinical effectiveness was variable. Significant reduction in the total leukocyte count in patients responding favorably
1208
TALBERT COOPER, CHARLES H. WATKINS
usually occurred within two to four weeks after the institution of treatment. Encouraging hematologic remissions were consistently followed by a I evidences of relapse in three to eight weeks after treatment was discontinued. Further, a urethane-refractory state rather commonly appeared in cases in which the response to treatment ,vas encouraging at first. This state seemed particularly likely to develop if treatment was completely suspended for a time and subsequently resumed. Some advantage appeared to re~ult from the continuous administration of small amounts of urethane even after remission was well established in an effort to prevent the development of a refractory state. TABLE RESULTS OF URETHANE THERAPY IN
1
20
CASES OF EARLY CHRONIC
MYELOCYTIC LEUKEMIA
Duration of Urethane Therapy, mo.
Results Subsequent I~,oentgen
Therapy
1-6
6-12
12-18
18-24
--
Satisfactory clinical and hematologic remission Satisfactory early remission: later refractory No appreciable effect on clinical course
o Patient living . • Patient dead.
0
0 0
o.
o.
••• ••
24-30 ---
0 ••
0
o.
0
0
Good
Poor
~ - _ . -
0 000
• ••
0
RESULTS OF TREATMENT
The response of patients in this series to the administration of urethane followed one of three general courses: 1. A satisfactory clinical and hematologic remission of the disease resulted and was sustained. The character of the remissions observed approximated those resulting from irradiation therapy with the usual decrease in the number of leukocytes in the peripheral.blood, a marked reduction in the percentage of abnormal immature cells in the peripheral blood and bone marrow, partial to complete relief of anemia when present, and reduction in the size of the spleen. 2. A satisfactory cliIiicaland hematologic remission ensued, but was succeeded, despite the continued administration of urethane, by relapse. A urethane-refractory state appeared to develop in such patients. 3. The progress of the disease was not appreciably influenced
URETHANE IN CHRONIC MYELOCy'rIC LEUKEMIA
1209
although in the majority of patients in this group temporary reductions in the total leukocyte count were observed. The results of treatment in the early and moderately advanced groups of patients are summarized in tables 1 and 2. The duration of treatment with urethane in each case also is indicated. In cases in which roentgen irradiation was subsequently employed under our supervision the results are tabulated. The Early Group. Satisfactory clinical and hematologic remissions were produced and sustained in 3 cases. In 1 patient treatment with urethane was discontinued after eight months because of the development of muscular aching, stiffness and headache. These symptoms TABLE 2 RESULTS OF URETHANE IN
17
CASES OF MODERATELY ADVANCED CHRONIC
MYELOCYTIC LEUKEMIA
Duration of Urethane Therapy, mo. 1-6
Satisfactory clinical and hematologic remission Satisfactory early remission: later refractory No appreciable effect on clinical course
o
•
6-12
12-18
18-24
Results Subsequent Roentgen Therapy Good
Poor
o 00. • • • • •• • ••
••
•
o
00
•• • ••
•
Patient living. Patient dead.
rapidly disappeared when administration of urethane was suspended and this patient's subsequent response to roentgen irradiation was satisfactory. Treatment of the other 2 patients has been continued for periods of nineteen and twenty-nine months respectively with relatively complete suppression of clinical and hematologic evidences of leukemia and with freedom from unpleasant toxic effects attributable to the drug. In 7 patients a definite remission lasting from two to sixteen months (average 10.2 months) was effected; however, resistance to this type of therapy: eventually developed and could not be overcome by increased dosage or pro~onged continuation of treatment. In 3 instances roentgen irradiation was then administered under our supervision with satisfactory results; an additional patient responded satisfactorily to similar treatment administered elsewhere. In the 3 remaining cases the disease progressed rapidly' to termination in an acute leukemic phase.
1210
TALBERT COOPER, CHARLES H. WATKINS
Of the 10 patients in this group who derived no apparent benefit from the action of urethane 7 have died. Five of the 10 patients had an encouraging early fall in the total leukocyte count but, in all other respects, the course of the disease was not measurably influenced by urethane. Roentgen irradiation which was administered after treatment with urethane in 4 cases was similarly ineffective. The Moderately Advanced Group. The single satisfactory remission achieved in this group has now been sustained for twenty-two months, during which time the patient has had a normal pregnancy and was delivered of a normal infant. Prior to the use of urethane satisfactory remissions had been produced in this case by a course of roentgen irradiation and two courses of treatment with radioactive phosphorus. She has now survived for approximately five years since the onset of symptoms. In 6 cases satisfactory early responses were followed within four to fourteen months (average 9 months) by the development of urethane refractory states. Thereafter the disease progressed rapidly to fatal termination in 3 cases, the course not being favorably influenced by roentgen therapy which was carried out in 2. However, 2 other patients in this group responded satisfactorily to the subsequent administration of roentgen irradiation. Urethane therapy produced no significant change in the course of the 10 remaining patients although in 9 patients of this group a temporary reduction of the total leukocyte count was effected. All cases terminated fatally three to sixteen months ·after the institution of therapy with urethane. Roentgen irradiation which was' also employed in 4 cases was similarly futile. GENERAL OBSERVATIONS
While, generally speaking, the response to treatment with urethane was more encouraging in the relatively early condition as might have been anticipated, it seems more significant that 10 of the 20 cases in this group were not measurably affected by the treatment. As is true of the response to most palliative agents currently employed, a poor response to urethane therapy appears to suggest a relatively poor prognosis (table 3). Exceptions occurred but patients presenting more marked degrees of splenomegaly responded less favorably to treatment. Although the enlargement of the spleen was often considerably reduced by urethane therapy; the degree of shrinkage was usually less marked than that commonly accomplished by irradiation therapy under similar circumstances. Previous therapeutic irradiation appeared to hav.e no specific effect on a patient's capacity to respond to urethane therapy. However, in
1211
URETHANE IN CHRONIC MYELOCYTIC LEUKEMIA
no instance were significantly beneficial effects obtained with urethane in cases in which irradiation-refractory states were present. The reverse was true with certain reservations. Patients for whom the use of urethane appeared entirely futile responded poorly when irradiation therapy was subsequently employed. However, many patients whose condition became resistant to the effects of urethane after initial satisfactory remissions had been produced with this treatment subsequently responded satisfactorily to roentgen irradiation. It is interesting, although in this small group of patients of no necessary significance, that the 3 patients continuing with urethane therapy after remissions of eighteen months or more are females-aged 26, 43 and 48 years. Two thirds of a group of patients surviving for periods of more TABLE 3 CHARACTER OF RESPONSE TO URETHANE AS A PROGNOSTIC INDICATOR
Response Satisfactory clinical and hematologic remission Satisfactory early remission: later refractory No appreciable effect on clinical course Total
Patients Total
Dead
4
13
6
20
17
37
23
than five years from the date of diagnosis of chronic myelocytic leukemia which were reviewed by Moffitt and Lawrence were women. The total leukocyte count of the peripheral blood together with the percentage of abnormal immature cells in the peripheral blood and bone marrow was reduced in some cases in which there was no other significant evidence of a favorable response. Berman and Axelrod observed similar results in cases in which on postmortem examination histologically undisturbed leukemic infiltrations were noted in the liver despite previous marked reduction in the number of leukocytes in the circulating blood. Twenty-three of the 37 patients receiving urethane therapy during the past three years are dead. Nine of these came under our observation during the terminal stages of their illnesses and 8 presented the features of acute transition of the leukemic process. Whether the action of urethane contributed to this change cannot be determined. Jaffe demonstrated the development of pulmonary adenomas and .hepatomas in mice receiving injections of urethane. A high incidence of terminal
1212
TALBERT COOPER, CHARLES H. WATKINS
acute leukemia also has been observed in cases of chronic leukemia treated with radioactive phosphorus.l° It may well be that the widespread use of blood transfusions and antibiotic substances has resulted in control of the effects of chronic anemia and intercurrent infections to the extent that the majority of aggressively treated patients will continue to succumb as the result of an acute transition of the process regardless of the palliative agent employed. ' In the 23 cases which have terminated fatally, the average duration of life from the onset of symptoms to death was twenty-seven months. Patients in our group who have survived thus far have had evidence of the disease for an average period of thirty months. It seems doubtful that the average duration of life for the entire group will be significantly prolonged. TOXICITY
Undesirable side .effects were commonly encountered but the degree of resultant subjective distress was usually directly proportional to the dosage employed and became tolerable when the dosage was reduced. Nausea, vomiting and other symptoms of gastro-intestinal irritation including so-called gas pains and diarrhea occurred at some time in the course of treatment in approximately 60 per cent of the patients. In only 3 instances, however, was it necessary to discontinue treatment on this account. Neither intravenous nor rectal routes of administration, which might mitigate the gastro-intestinal disturbances to a considerable degree, were employed in these cases. In addition to symptoms referable to the gastro-intestinal tract, patients complained of lethargy, loss of "pep," feeling "half sick all the time," dizziness, muscular aching, muscular stiffness and headache. ,:On some occasions it was felt that the underlying disease contributed to these difficulties but most patients were much improved subjectively in so far as these rather vague complaints were concerned when the amount of urethane administered was markedly reduced or this treatment was discontinued entirely. Serious depression of hematopoiesis was not observed in this series and rare difficulties of this sort have been reported by others employing the materia1. 20 • 22 Although the production of renal glomerular lesions and hepatic venocapillary injury in mice and rats treated with urethane has been reported,4. 16 there was no evidence of such damage resulting from treatment in this series. In Huggins' case of toxic hepatitis, which developed after the treatment of metastatic carcinoma of the prostate with urethane, the dosage employed was 9 gm. daily for thirty-three days.
URErl'HANE IN CHRONIC MYELOCyrrIC LEUKl!}MIA
1213
COMMENT
The results of this study indicate that the use of urethane contributes little to the palliative treatment of patients with chronic myelocytic leukemia. The practical advantage of an agent which may be administered orally seems clearly outweighed by its general ineffectiveness and the bothersome side effects resulting from its administration. Roentgen therapy, which may be expected to produce satisfactory temporary palliation of symptoms in 90 per cent of cases of this type, remains the most consistently effective mode of treatment generally available at present. Although roentgen therapy often resulted in satisfactory remissions after the development of urethane refractory states in cases in the series, urethane therapy contributed nothing to the patient whose condition had become resistant to the effects of ionizing radiation. We have employed small doses of urethane in several cases of chronic myelocytic leukemia in which roentgen therapy was being given periodically in an effort to prolong the roentgen-induced remission. Ilesults thus far have been inconclusive but do not appear to justify the general adoption of this combination of therapeutic agents. Urethane, however, represents an addition to the rather large body of agents having some demonstrable, if not therapeutically important, effect on leukemic processes. While the action of urethane has been attributed to its capacity for direct action on cellular metabolic activity, most apparent on actively dividing cells, it may well be that its modus operandi is indirect and that the other various factors including intercurrent infections, which may produce temporary remissions in patients with leukemia act through a common pathway. Fragmentary evidence is available to suggest that urethane may produce adrenal cortical stimulation. Hawkins and Murphy found that in rabbits or rats anesthetized with urethane the carbon dioxide combining power and pH of the whole blood are increased to the point of marked uncompensated alkalosis, which reaches a maximum twenty-four hours after anesthetization and persists for forty-eight hours. This alkalosis is accompanied by a decrease in number of circulating lymphocytes and an increase in polymorphonuclear neutrophils. Irradiation of the animals provoked similar changes as did the intravenous injection of sodium bicarbonate. Boyd and Perry found the potassium content of bronchial secretions two to four times higher in cats under urethane anesthesia than in decerebrate cats. At the same time the average concentration of serum potassium was reduced from 21.5 to 17.8 mg. per 100 cc. Kirschbaum and I-Ju, however, have been able to obtain the usual "urethane effect" in adrenalectomized leukemic mice.
1214
'rALHER1' COOPER, CHAHLES H. WA'rKINS
SUMMARY
Satisfactory sustained remissions were achieved in 4 of 37 cases of chronic myelocytic leukemia in which ethyl carbamate (urethane) was administered. In an additional 13 cases significant early remissions were followed by the development of a urethane-refractory state and the appearance of clinical and hematologic relapse. In the remaining 20 cases treatment with ethyl carbamate was not clinically effective although in 14 cases a moderate reduction in the total leukocyte count of the peripheral blood was effected. The administration of therapeutically active amounts of urethane resulted in distressing side effects in many instances although no serious side effects were observed. Ionizing roentgen radiation is much more consistently effective in the palliative treatment of chronic myelocytic leukemia than is urethane. REFERENCES 1. Bedinger, P. L., Poncher, H. G. and Limarzi, L. R.: F~ffect of Urethane on Leucemia. J. Lab. & Clin. Med. 32 (pt. 2): 1394-1395,1947. 2. Berman, Lawrence and Axelrod, A. R.: Effect of Urethane on Malignant Diseases; Clinical, Hematologic and Histologic Observations on Patients With Carcinoma, Leukemia and Related Diseases. Am. J. Clin. Path. 18: 104-129 (Feb.) 1948. 3. Boyd, E. M. and Perry, W. F.: Urethane Administration and Potassium Content of Bronchial Secretions in the Cat. Proc. Soc. Exper. BioI. & Med. 57: 334-335 (Dec.) 1944. 4. Doljanski, L. and Rosin, A.: Studies on the Early Changes in the Livers of Rats Treated With Various Toxic Agents, With Especial Reference to the Vascular Lesions. 1. The Histology of the Rat's Liver in Urethane Poisoning. Am. J. Path. 20: 945-960 (Sept.) 1944. 5. Farmer, Laurence: The Use of Urethane in Symptomatic Treatment of Bronchial Asthma. J. Lab. & Clin. Med. 24: 453-454 (Feb.) 1939. 6. Geiersbach, Ute: TIber den Einfluss del' N arkose (Urethan) auf Gewebekulturen. Arch. f. expel'. Zellforsch. 23: 210-219, 1939. 7. Goodman, L. S. and Gilman, Alfred: The Pharmacological Basis of Therapeutics; a Textbook of Pharmacology, Toxicology and Therapeutics for Physicians and Medical Students. New York, The Macmillan Company, 1941, 1383 pp. 8. Guyer, M. F. and Claus, P. E.: Effects of Urethane (Ethyl Carbamate)on Mitosis. Proc. Soc. Expel'. BioI. & Med. 64: 3-5 (Jan.) 1947. 9. Haddow, Alexander and Sexton, W. A.: Influence of Carbamic Esters (Urethanes) on Experimental Animal Tumours. Nature, London. 157: 500-503 (Apr. 20) 1946. 10. Hall, B. E. and Watkins, C. H.: Radiophosphorus in the Treatment of Blood Dyscrasias. M. CLIN. NORTH AMERICA. 31: 810-840 (July) 1947. 11. Hawkins, J. A. and Murphy, J. B.: The Effect of Ethyl Urethane Anesthesia on the Acid-base Equilibrium and Cell Contents of the Blood. J.Exper. Med. 42: 609-618 (Nov. 1) 1925. 12. Hirschboeck, J. S., Lindert, M. C. F., Chase, Jules and Calvy, T. L.: Effects of Urethane in the Treatment of Leukemia 'and Metastatic Malignant Tumors. J.A.M.A. 136: 90-94 (Jan. 10) 1948. 13. Huggins, Charles, Yu, S. T. and Jones, Ralph, Jr.: Inhibitory Effects of Ethyl Carbamate on Prostatic Cancer. Science. n.s. 106: 147-148 (Aug. 15) 1947.
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14. Jaffe, Rudolf: flistological Findinga in Lungs and Livers of Rats Treated With Ethyl Urethane. Cancer Research. 7: 111-112 (Feb.) 1947. 15. Johnson, F. H.: Mechanism of P-aminobenzoic Acid Action and the Parallel F~ffects of Ethyl Carbamate (Urethane). Science. n.s. 95: 104-105 (Jan. 23) 1942. 16. Kirschbaum, ~Arthur and Bell, E. T.: Induction of Renal Glomerular Lesions by Urethane in Inbred Mice Susceptible to Spontaneous Glomerulonephritis. Proc. Soc. Expel'. BioI. & Med. 64: 71-72 (Jan.) 1947. 17. Kirschbaum, Arthur and Lu, C. S.: Effect of Urethane on Normal and Leukemic Hemopoietic Tissues of the Mouse. Unio Internationalis Contra Cancrum. Aeta. 6: 530-533, 1949. 18. Lefebvre, Joseph: Similitude des actions cytologiques exercees par Ie phenylurethane et la colchicine sur des plantules vegetales. Compt. rend. Acad. d. sc. 208: 301-304 (Jan. 23) 1939. 19. Moffitt, H. C., Jr. and LaNrence, J. H.: Chronic Leukemia of Long Duration: With a Report of 31 Cases With a Duration of Over Five Years. Ann. Int. Med. 30: 778-790 (Apr.) 1949. 20. Paterson, Edith, Haddow, Alexander, Ap Thomas, Inez and Watkinson, Jean M.: Leukemia Treated With Urethane; Compared With Deep X-ray Therapy. Lancet. 1: 677-682 (May 11) 1946. 21. Watkins, C. H. i Cooper, Talbert and Giffin, H. Z.: The Use of Urethane (Ethyl Carbamate) in the Treatment of Leukemia; a Preliminary Report. Blood. 3: 892-895 (Aug.) 1948. 22. Webster, J. J.: Urethane in Leukemia. J.A.M.A. 135: 901-903 (Dec. 6) 1947. 23. Weinstein, Louis and McDonald, Alice: 'Tlhe Action of Urea and SOIne of Its Derivatives on Bacteria. 1. Bacteriostatic and Bactericidal Effects of Urea and Urethane ..J. Immunol. 54: 117-130 (Oct.) 1946. 24:. Weinstein, I.Jouis and McDonald, Alice: The Action of Urea and Some of Its Derivatives on Bacteria. II. The A.ntibacterial Activity of Combinations of Urea and Urethane With Sulfonamides and the Effect of the Carbamates on Para-aminobenzoic Acid and on the Solubility of SulfonaInide3. J. Immunol. 54: 131-144 (Oct.) 1946.