- Email: [email protected]
Alteration of radiation-induced hematotoxicity by amifostine
Int. J. Radiation Oncology Biol. Phys., Vol. 51, No. 4, pp. 947–951, 2001 Copyright © 2001 Elsevier Science Inc. Printed in the USA. All rights reserved 0360-3016/01/$–see front matter
PII S0360-3016(01)01710-2
CLINICAL INVESTIGATION
Head and Neck
ALTERATION OF RADIATION-INDUCED HEMATOTOXICITY BY AMIFOSTINE FELIX MOMM, M.D.,* CHRISTINE BECHTOLD,* VOLKER RUDAT, M.D.,† VRATISLAV STRNAD, M.D.,‡ ALEXANDER TSEKOS, M.D.,* KARIN FISCHER, M.D.,* AND MICHAEL HENKE, M.D.* *Department of Radiotherapy, University Clinic Freiburg, Freiburg, Germany; †Department of Clinical Radiology, University Clinic Heidelberg, Heidelberg, Germany; ‡Department of Radiotherapy, University Erlangen-Nu¨rnberg, Erlangen, Germany Purpose: To investigate whether amifostine can reduce radiation hematotoxicity. Patients and Methods: Seventy-three patients undergoing radiotherapy for squamous cell carcinoma of the head and neck at the university clinics of Freiburg, Heidelberg, and Erlangen were evaluated. All received 60 Gy (50 –70 Gy) at 5 ⴛ 2 Gy fractions per week employing standard techniques. Thirty-five were randomized to receive 200 mg/m2 amifostine i.v. 30 min before radiation; 38 served as control patients. Blood counts (total n ⴝ 501) were determined before, during, and while completing radiotherapy. Changes of leukocyte, platelet, and hemoglobin levels were determined and compared using the t test. Results: The blood hemoglobin level and the platelet count were not affected by irradiation, for either the amifostine-treated or control patients. Similarly, the leukocyte counts of amifostine-treated patients did not change during irradiation. However, control patients experienced a decrease in leukocyte count from 8.1 ⴛ 103/mm3 to 5.8 ⴛ 103/mm3 (difference: 2.3 ⴛ 103/mm3). This seems to be line specific: Whereas amifostine does not affect lymphocyte count, a radiation-induced decrease of neutrophil granulocytes seems to be prevented. Conclusion: Amifostine protects from radiation hematotoxicity, particularly affecting the granulocytopoiesis. These data confirm results from our former study. © 2001 Elsevier Science Inc. Amifostine, Leukocytes, Radiotherapy, Hematotoxicity.
ters, and consent was obtained for each patient according to the current revision of the Helsinki Declaration. The study was conducted according to Good Clinical Practice (GCP) standards and audited by an independent auditor.
INTRODUCTION Radiation induces leukocytopenia with relative lymphocytopenia. The hematotoxicity after chemotherapy can be reduced by amifostine (1–12). An amifostine radioprotection of the hematopoiesis is reported for large radiation volumes (13–14). We investigated whether amifostine might affect hematotoxicity of patients undergoing radiotherapy for head-and-neck cancer. This study will expand our former observations (15).
Patients Trial WR-38 is closed. Analysis of primary end points, as well as trial details, has been published (16). Here we investigated 501 blood counts from 73 patients and, further, 132 differential cell counts from 42 patients. All patients were treated in Freiburg, Heidelberg, and Erlangen. They were irradiated for squamous cell carcinoma of the headand-neck region with curative intent: 17 with primary, definitive radiotherapy, and 56 postoperatively. Patients without any blood count before they received 10 Gy or after they received 50 Gy were not considered for analysis of cell count. For patient characteristics, see Table 1.
PATIENTS AND METHODS Design Data on blood hemoglobin concentration, leukocyte and platelet counts, and differential cell counts were monitored and documented for patients with head-and-neck cancer treated within a multicenter study (WR-38). This trial was prospective, randomized, and open labeled and examined whether amifostine can protect salivary glands of patients undergoing radiotherapy of the head-and-neck area. It was approved by the ethics committees at all participating cen-
Amifostine medication Patients were randomly allocated into one of the two study arms: (1) radiotherapy plus amifostine 200 mg/m2, or
Reprint requests to: Dr. med. Felix Momm, Radiologische Universita¨tsklinik, Abteilung fu¨r Strahlenheilkunde, Hugstetter Str. 55, D-79106 Freiburg i. Br., Germany. Tel: 49/(0)761/270-3862; Fax: 49/(0)761/270-3982; E-mail: [email protected]
This study was supported by USB Pharma Ltd., Watford, UK. Acknowledgments—We thank Mrs. I. Liebhardt and Mrs. S. Ahlers for their help in data documentation. Received Mar 15, 2001, and in revised form Jun 7, 2001. Accepted for publication Jun 14, 2001. 947
948
I. J. Radiation Oncology
● Biology ● Physics
Table 1. Demographic data With amifostine Arm n Tumor location Hypopharynx Larynx Oropharynx Oral cavity Unknown primary Therapy Postop. XRT Definitive XRT Dose “post XRT” (average)
Controls
35
38
3 3 19 10 0
7 9 14 7 1
28 7 59.1 Gy
28 10 59.8 Gy
Figures represent numbers of patients or dose. Abbreviation: XRT ⫽ external beam irradiation.
(2) radiotherapy alone. Amifostine was administered i.v. in 50 –250 mL NaCl 0.9% daily within a maximum interval of 30 min before every fraction. The average cumulative amifostine dose per patient was 10,600 mg (minimum 2,700 mg, maximum 15,500 mg). Radiotherapy For the radiotherapy, standard dose/fractionation protocols (5 ⫻ 2 Gy/week) were followed. A 6-MeV linear accelerator was used. Radiation volume and total dose were determined by the WR-38 trial (16). To check for eventual differences in dose density between amifostine-treated and control patients, dose over
Volume 51, Number 4, 2001
time scattering was performed for both groups. A total of 787 measurements were available (Fig. 1). Clinical tests All patients were monitored daily during the course of radiotherapy. Blood samples were taken once a week, and cell counts and hemoglobin concentrations were determined. Primary variables It was hypothesized that amifostine might protect from radiation-induced hematotoxicity. Thus, changes were evaluated in hematologic parameters during a radiotherapy course for patients treated with or without amifostine. The parameters analyzed were hemoglobin concentration, platelet count, and leukocyte count (including differential). Statistical analyses Differences were determined between blood cell count and hemoglobin level observed before the patient received 10 Gy and after he was treated with at least 50 Gy. These differences were compared between the amifostine group and the control group using a t test. test. In a further analysis, differences in cell counts were related to the applied radiation dose. A linear regression was made to show different cell counts (cell count at ⬍10 Gy to cell count at actual dose) and radiation doses. A comparison was made between the steepness of the regression lines for the amifostine group and the control group. Statistical tests were performed by JMP version 3.1.6.2. (SAS).
Fig. 1. Dose distribution for amifostine-treated and control patients (radiation dose [Gy], treatment time [days]), (filled circles ⫽ amifostine; open circles ⫽ controls). Regression lines for both groups are shown (solid ⫽ amifostine; dotted ⫽ controls).
Alteration of radiation-induced hematotoxicity by amifostine
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Fig. 2. Differences in leukocyte count from the start of radiation (⬍10 Gy) to a given dose are depicted (filled circles, amifostine; open circles, controls). Linear regression lines for both groups are shown (solid, amifostine; dotted, controls).
RESULTS Demographic data Complete data on tumor site, staging, treatment (surgery and radiotherapy), hemoglobin level, and platelet and leukocyte count were available for all patients. Differential blood cell counts were available for 42 patients. Table 1 depicts the demographic and treatment-related parameters. There was a fairly even distribution between the two randomized groups as far as gender, tumor localization, stage, and treatment parameters are concerned. Both groups received a comparable radiation dose over the treatment period (Fig. 1).
to ⬎50 Gy ⫽ 23 ⫻ 103/mm3) for the control patients (p ⫽ 0.96; two-tailed t test for independent groups).
Hemoglobin levels The average hemoglobin level at baseline was 13.4 g/dL for the amifostine-treated patients and 13.5 g/dL for the control patients. For both, the hemoglobin levels did not change significantly during radiotherapy. At ⬎50 Gy, amifostine-treated patients had a hemoglobin level of 13.0 g/dL (delta ⬍10 to ⬎50 Gy ⫽ 0.4 g/dL); the level for control patients was 13.5 g/dL (delta ⬍10 to ⬎50 Gy ⫽ 0.0 g/dL) (p ⫽ 0.21; two-tailed t test for independent groups).
Leukocytes Amifostine-treated patients had an average leukocyte count at baseline of 7.5 ⫻ 103/mm3 as compared to 8.1 ⫻ 103/mm3 for control patients. Amifostine-treated patients experienced a minor decline in leukocyte count during radiotherapy. At ⬎50 Gy, 7.0 ⫻ 103 leukocytes/mm3 were determined (delta ⬍10 to ⬎50 Gy ⫽ 0.5 ⫻ 103/mm3). However, control patients showed significantly reduced leukocyte counts: At ⬎50 Gy, only 5.8 ⫻ 103/mm3 leukocytes could be determined (delta ⬍10 to ⬎50 Gy ⫽ 2.3 ⫻ 103/mm3) (p ⬍ 0.005; two-tailed t test for independent groups). Furthermore, leukocyte counts (n ⫽ 501) were investigated during the entire radiotherapy course. Differences among leukocytes at ⬍10 Gy and at a given dose, x Gy, were determined and related to radiation dose (Fig. 2). Amifostine-treated patients showed a smaller decrease in leukocytes over the dose (⫺11 leukocytes/mm3/Gy) than control patients (⫺35 leukocytes/mm3/Gy).
Platelets The average platelet count at baseline for amifostinetreated patients was 295 ⫻ 103/mm3 and 318 ⫻ 103/mm3 for control patients. Again, platelet counts did not change significantly during radiotherapy: 270 ⫻ 103/mm3 at ⬎50 Gy (delta ⬍10 to ⬎50 Gy ⫽ 25 ⫻ 103/mm3) for the amifostine-treated patients and 295 ⫻ 103/mm3 (delta ⬍10
Differential cell counts For differential cell counts available (n ⫽ 132), values of neutrophil granulocytes and lymphocytes for both treatment groups were related to the radiation dose (Fig. 3). No difference was observed between amifostine-treated and control patients for the decline in lymphocytes (both groups: ⫺21 lymphocytes/mm3/Gy). However, neutrophil granulo-
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I. J. Radiation Oncology
● Biology ● Physics
Volume 51, Number 4, 2001
Fig. 3. Lymphocyte counts and neutrophil granulocyte counts at a given dose are depicted (filled circles at left, amifostine; open circles at right, controls). Linear regression lines are shown.
cytes seemed to increase during radiotherapy of amifostinetreated patients (⫹10 neutrophil granulocytes/mm3/Gy); in contrast, control patients showed a decline (⫺18 neutrophil granulocytes/mm3/Gy) (Fig. 3).
DISCUSSION As well as technical developments, a pharmacologic modulation of radiosensitivity is expected to increasingly influence modern radiotherapy. Thus, radioprotection may not only provide a better quality of life for patients, but eventually allow an increase in radiation dose and improvement in cure rate. Amifostine, a scavenger of radiationinduced free radicals, is one of the most intensively studied radioprotectors (1–12). It is known to protect parotidea and small salivary glands from radiation injuries (17–22). Particularly, the occurrence of acute and chronic radiation xerostomia can be effectively diminished (16); as a consequence, dental health will be retained (10). Though the hematotoxicity of total body irradiation cannot be prevented (23), patients undergoing half-body irradiation experience an improved hematopoiesis when treated with amifostine (5). Wondering whether the hematopoietic radioprotection might help to better understand the mechanism of amifostine’s activity, we undertook the investigation of hemato-
logic parameters pertaining to patients given small volumes of radiation. Our results clearly demonstrate that even a 60 Gy irradiation of small volumes, as applied to patients with headand-neck cancer, decreases leukocytes from 8.1 ⫻ 103/mm3 to 5.8 ⫻ 103/mm3, as well as platelets from 318 ⫻ 103/mm3 to 270 ⫻ 103/mm3; the blood hemoglobin concentration, on the other hand, essentially persists during the radiotherapy course (13.5 g/dL). The platelet count is not affected by amifostine. However, amifostine treatment will counteract the decline in the number of leukocytes (7.5 ⫻ 103/mm3 to 7.0 ⫻ 103/mm3). This is caused by an increase in the absolute amount of neutrophil granulocytes. The radiation-induced decrease in lymphocytes is not affected by amifostine (Fig. 3). The prevention of leukocytopenia by amifostine is statistically significant when analyzed with a two-tailed t test (p ⬍ 0.005). Though a difference of dose per week between amifostine patients and control patients cannot definitely be ruled out, it seems unlikely: The dose densities (Gy per week) for both amifostine and control patients are comparable (Fig. 1). Furthermore, data on additional populations from other institutions confirm our previous observation (15).
Alteration of radiation-induced hematotoxicity by amifostine
We did not investigate the mechanism of amifostine’s selective radioprotective activity on the granulopoiesis. A difference in radiosensitivity among different cell lines may be causative. A more likely cause is the difference in enzyme patterns among blood cells. Myelopoietic cells are known to express alkaline phosphatase (24). This enzyme is essential for the uptake and metabolism (6) of amifostine, to finally enable its radioprotective potential. It is of note that neutrophil granulocytes are nondividing cells. Thus, radiation-induced granulocytopenia must be the consequence of irradiating specific circulating myelopoietic stem cells. Because amifostine does
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951
not affect the decrease in platelet count after radiotherapy, we speculate that thrombopoietic stem cells tend to circulate less often in the peripheral blood. Clearly, in patients undergoing radiotherapy, the mechanism of amifostine’s activity on granulopoiesis needs further investigation to broaden our knowledge and eventually guide us toward the drug’s use in protecting other tissues, as well. We conclude that amifostine protects the hematopoiesis from radiation injury, particularly the neutrophil granulopoietic lineage. The underlying mechanism may be related to cellular enzymes and should be further studied.
REFERENCES 1. Alberts DS, Bleyer WA. Future development of amifostine in cancer treatment. Semin Oncol 1996;23:90 –99. 2. Budd GT. Amifostine and chemotherapy-related thrombocytopenia. Semin Oncol 1996;23:49 –52. 3. Budd GT, Ganapathi R, Bukowski RM, et al. Clinical effects of amifostine (EthyolR) in patients treated with carboplatin. Eur J Cancer 1996;32A(Suppl. 4):S43–S45. 4. Bukowski RM. The need for cytoprotection. Eur J Cancer 1996;32A(Suppl. 4):S2–S4. 5. Cagnoni PJ, Jones RB, Bearman SI, et al. Use of amifostine in bone marrow purging. Semin Oncol 1996;23:44 – 48. 6. Capizzi RL. The preclinical basis for broad-spectrum selective cytoprotection of normal tissues from cytotoxic therapies by amifostine (EthyolR). Eur J Cancer 1996;32A(Suppl. 4):S5– S16. 7. Glover D, Glick JH, Weiler C, et al. Phase I/II trials of WR-2721 and cis-platinum. Int J Radiat Oncol Biol Phys 1986;12:1509 –1512. 8. List AF, Heaton R, Glinsmann-Gibson B, et al. Amifostine protects primitive hematopoietic progenitors against chemotherapy cytotoxicity. Semin Oncol 1996;23:58 – 63. 9. Milas L, Hunter N, Ito H, et al. Effect of tumor type, size, and endpoint on tumor radioprotection by WR-2721. Int J Radiat Oncol Biol Phys 1984;10:41– 48. 10. Rudat V, Meyer J, Momm F, et al. Protective effect of amifostine on dental health after radiotherapy of the head and neck. Int J Radiat Oncol Biol Phys 2000;48(5):1339 –1343. 11. Schuchter LM. Exploration of platinum-based dose-intensive chemotherapy strategies with amifostine (EthyolR). Eur J Cancer 1996;32A(Suppl. 4):S40 –S42. 12. Schiller JH. High-dose cisplatin and vinblastine plus amifostine for metastatic non-small cell lung cancer. Semin Oncol 1996;23:78 – 82. 13. Tannehill SP, Mehta MP. Amifostine and radiation therapy: Past, present, and future. Semin Oncol 1996;23:69 –77. 14. Constine LS, Zagars G, Rubin P, et al. Protection by WR-2721 of human bone marrow function following irradiation. Int J Radiat Oncol Biol Phys 1986;12:1505–1508.
15. Momm F, Bechtold C, Fischer K, Tsekos A, Henke M. Alteration of radiation induced hematotoxicity by amifostine (EthyolR). Strahlenther Onkol 1999;175(Suppl. IV):2–5. 16. Brizel DM, Wasserman TH, Henke M, et al. Phase III randomized trial of amifostine as a radioprotector in head and neck cancer. J Clin Oncol 2000;18:3339 –3345. 17. Altmann S, Hoffmanns H. Cytoprotection with amifostine in radiotherapy or combined radio-chemotherapy of head and neck cancer. Strahlenther Onkol 1999;175(Suppl. IV):30 –33. 18. Bohuslavizki KH, Klutmann S, Brenner W, et al. Radioprotection of salivary glands by amifostine in high-dose radioiodine treatment. Strahlenther Onkol 1999;175(Suppl. IV):6 – 12. 19. Bu¨ ntzel J, Glatzel M, Schuth J, et al. Cytoprotection with amifostine in the simultaneous radio-chemotherapy of recurrent head and neck cancer. Strahlenther Onkol 1999; 175(Suppl. IV):37– 40. 20. Scho¨ neka¨ s KG, Wagner W, Prott FJ. Amifostine—a radioprotector in locally advanced head and neck tumors. Strahlenther Onkol 1999;175(Suppl. IV):27–29. 21. Schultze J, Kimmig B. Results of definitive combined radiochemotherapy in head and neck tumors with simultaneous salivary gland protection by amifostine administration. Strahlenther Onkol 1999;175(Suppl. IV):13–17. 22. Vacha P, Marx M, Engel A, et al. Acute toxicity of postoperative radiochemotherapy with amifostine vs radiochemotherapy alone in head and neck cancer patients. Preliminary results of a randomized trial. Strahlenther Onkol 1999; 175(Suppl. IV):18 –22. 23. Coia L, Krigel R, Hanks G, et al. A Phase I study of WR-2721 in combination with total body irradiation (TBI) in patients with refractory lymphoid malignancies. Int J Radiat Oncol Biol Phys 1992;22:791–794. 24. Jandl JH. Chronic myeloproliferative syndromes. In: Jandl JH, editor. Blood: Textbook of hematology. 2nd ed. Boston-New York-Toronto-London: Little, Brown and Co.; 1996. p. 903– 960.
PII S0360-3016(01)01710-2
CLINICAL INVESTIGATION
Head and Neck
ALTERATION OF RADIATION-INDUCED HEMATOTOXICITY BY AMIFOSTINE FELIX MOMM, M.D.,* CHRISTINE BECHTOLD,* VOLKER RUDAT, M.D.,† VRATISLAV STRNAD, M.D.,‡ ALEXANDER TSEKOS, M.D.,* KARIN FISCHER, M.D.,* AND MICHAEL HENKE, M.D.* *Department of Radiotherapy, University Clinic Freiburg, Freiburg, Germany; †Department of Clinical Radiology, University Clinic Heidelberg, Heidelberg, Germany; ‡Department of Radiotherapy, University Erlangen-Nu¨rnberg, Erlangen, Germany Purpose: To investigate whether amifostine can reduce radiation hematotoxicity. Patients and Methods: Seventy-three patients undergoing radiotherapy for squamous cell carcinoma of the head and neck at the university clinics of Freiburg, Heidelberg, and Erlangen were evaluated. All received 60 Gy (50 –70 Gy) at 5 ⴛ 2 Gy fractions per week employing standard techniques. Thirty-five were randomized to receive 200 mg/m2 amifostine i.v. 30 min before radiation; 38 served as control patients. Blood counts (total n ⴝ 501) were determined before, during, and while completing radiotherapy. Changes of leukocyte, platelet, and hemoglobin levels were determined and compared using the t test. Results: The blood hemoglobin level and the platelet count were not affected by irradiation, for either the amifostine-treated or control patients. Similarly, the leukocyte counts of amifostine-treated patients did not change during irradiation. However, control patients experienced a decrease in leukocyte count from 8.1 ⴛ 103/mm3 to 5.8 ⴛ 103/mm3 (difference: 2.3 ⴛ 103/mm3). This seems to be line specific: Whereas amifostine does not affect lymphocyte count, a radiation-induced decrease of neutrophil granulocytes seems to be prevented. Conclusion: Amifostine protects from radiation hematotoxicity, particularly affecting the granulocytopoiesis. These data confirm results from our former study. © 2001 Elsevier Science Inc. Amifostine, Leukocytes, Radiotherapy, Hematotoxicity.
ters, and consent was obtained for each patient according to the current revision of the Helsinki Declaration. The study was conducted according to Good Clinical Practice (GCP) standards and audited by an independent auditor.
INTRODUCTION Radiation induces leukocytopenia with relative lymphocytopenia. The hematotoxicity after chemotherapy can be reduced by amifostine (1–12). An amifostine radioprotection of the hematopoiesis is reported for large radiation volumes (13–14). We investigated whether amifostine might affect hematotoxicity of patients undergoing radiotherapy for head-and-neck cancer. This study will expand our former observations (15).
Patients Trial WR-38 is closed. Analysis of primary end points, as well as trial details, has been published (16). Here we investigated 501 blood counts from 73 patients and, further, 132 differential cell counts from 42 patients. All patients were treated in Freiburg, Heidelberg, and Erlangen. They were irradiated for squamous cell carcinoma of the headand-neck region with curative intent: 17 with primary, definitive radiotherapy, and 56 postoperatively. Patients without any blood count before they received 10 Gy or after they received 50 Gy were not considered for analysis of cell count. For patient characteristics, see Table 1.
PATIENTS AND METHODS Design Data on blood hemoglobin concentration, leukocyte and platelet counts, and differential cell counts were monitored and documented for patients with head-and-neck cancer treated within a multicenter study (WR-38). This trial was prospective, randomized, and open labeled and examined whether amifostine can protect salivary glands of patients undergoing radiotherapy of the head-and-neck area. It was approved by the ethics committees at all participating cen-
Amifostine medication Patients were randomly allocated into one of the two study arms: (1) radiotherapy plus amifostine 200 mg/m2, or
Reprint requests to: Dr. med. Felix Momm, Radiologische Universita¨tsklinik, Abteilung fu¨r Strahlenheilkunde, Hugstetter Str. 55, D-79106 Freiburg i. Br., Germany. Tel: 49/(0)761/270-3862; Fax: 49/(0)761/270-3982; E-mail: [email protected]
This study was supported by USB Pharma Ltd., Watford, UK. Acknowledgments—We thank Mrs. I. Liebhardt and Mrs. S. Ahlers for their help in data documentation. Received Mar 15, 2001, and in revised form Jun 7, 2001. Accepted for publication Jun 14, 2001. 947
948
I. J. Radiation Oncology
● Biology ● Physics
Table 1. Demographic data With amifostine Arm n Tumor location Hypopharynx Larynx Oropharynx Oral cavity Unknown primary Therapy Postop. XRT Definitive XRT Dose “post XRT” (average)
Controls
35
38
3 3 19 10 0
7 9 14 7 1
28 7 59.1 Gy
28 10 59.8 Gy
Figures represent numbers of patients or dose. Abbreviation: XRT ⫽ external beam irradiation.
(2) radiotherapy alone. Amifostine was administered i.v. in 50 –250 mL NaCl 0.9% daily within a maximum interval of 30 min before every fraction. The average cumulative amifostine dose per patient was 10,600 mg (minimum 2,700 mg, maximum 15,500 mg). Radiotherapy For the radiotherapy, standard dose/fractionation protocols (5 ⫻ 2 Gy/week) were followed. A 6-MeV linear accelerator was used. Radiation volume and total dose were determined by the WR-38 trial (16). To check for eventual differences in dose density between amifostine-treated and control patients, dose over
Volume 51, Number 4, 2001
time scattering was performed for both groups. A total of 787 measurements were available (Fig. 1). Clinical tests All patients were monitored daily during the course of radiotherapy. Blood samples were taken once a week, and cell counts and hemoglobin concentrations were determined. Primary variables It was hypothesized that amifostine might protect from radiation-induced hematotoxicity. Thus, changes were evaluated in hematologic parameters during a radiotherapy course for patients treated with or without amifostine. The parameters analyzed were hemoglobin concentration, platelet count, and leukocyte count (including differential). Statistical analyses Differences were determined between blood cell count and hemoglobin level observed before the patient received 10 Gy and after he was treated with at least 50 Gy. These differences were compared between the amifostine group and the control group using a t test. test. In a further analysis, differences in cell counts were related to the applied radiation dose. A linear regression was made to show different cell counts (cell count at ⬍10 Gy to cell count at actual dose) and radiation doses. A comparison was made between the steepness of the regression lines for the amifostine group and the control group. Statistical tests were performed by JMP version 3.1.6.2. (SAS).
Fig. 1. Dose distribution for amifostine-treated and control patients (radiation dose [Gy], treatment time [days]), (filled circles ⫽ amifostine; open circles ⫽ controls). Regression lines for both groups are shown (solid ⫽ amifostine; dotted ⫽ controls).
Alteration of radiation-induced hematotoxicity by amifostine
● F. MOMM et al.
949
Fig. 2. Differences in leukocyte count from the start of radiation (⬍10 Gy) to a given dose are depicted (filled circles, amifostine; open circles, controls). Linear regression lines for both groups are shown (solid, amifostine; dotted, controls).
RESULTS Demographic data Complete data on tumor site, staging, treatment (surgery and radiotherapy), hemoglobin level, and platelet and leukocyte count were available for all patients. Differential blood cell counts were available for 42 patients. Table 1 depicts the demographic and treatment-related parameters. There was a fairly even distribution between the two randomized groups as far as gender, tumor localization, stage, and treatment parameters are concerned. Both groups received a comparable radiation dose over the treatment period (Fig. 1).
to ⬎50 Gy ⫽ 23 ⫻ 103/mm3) for the control patients (p ⫽ 0.96; two-tailed t test for independent groups).
Hemoglobin levels The average hemoglobin level at baseline was 13.4 g/dL for the amifostine-treated patients and 13.5 g/dL for the control patients. For both, the hemoglobin levels did not change significantly during radiotherapy. At ⬎50 Gy, amifostine-treated patients had a hemoglobin level of 13.0 g/dL (delta ⬍10 to ⬎50 Gy ⫽ 0.4 g/dL); the level for control patients was 13.5 g/dL (delta ⬍10 to ⬎50 Gy ⫽ 0.0 g/dL) (p ⫽ 0.21; two-tailed t test for independent groups).
Leukocytes Amifostine-treated patients had an average leukocyte count at baseline of 7.5 ⫻ 103/mm3 as compared to 8.1 ⫻ 103/mm3 for control patients. Amifostine-treated patients experienced a minor decline in leukocyte count during radiotherapy. At ⬎50 Gy, 7.0 ⫻ 103 leukocytes/mm3 were determined (delta ⬍10 to ⬎50 Gy ⫽ 0.5 ⫻ 103/mm3). However, control patients showed significantly reduced leukocyte counts: At ⬎50 Gy, only 5.8 ⫻ 103/mm3 leukocytes could be determined (delta ⬍10 to ⬎50 Gy ⫽ 2.3 ⫻ 103/mm3) (p ⬍ 0.005; two-tailed t test for independent groups). Furthermore, leukocyte counts (n ⫽ 501) were investigated during the entire radiotherapy course. Differences among leukocytes at ⬍10 Gy and at a given dose, x Gy, were determined and related to radiation dose (Fig. 2). Amifostine-treated patients showed a smaller decrease in leukocytes over the dose (⫺11 leukocytes/mm3/Gy) than control patients (⫺35 leukocytes/mm3/Gy).
Platelets The average platelet count at baseline for amifostinetreated patients was 295 ⫻ 103/mm3 and 318 ⫻ 103/mm3 for control patients. Again, platelet counts did not change significantly during radiotherapy: 270 ⫻ 103/mm3 at ⬎50 Gy (delta ⬍10 to ⬎50 Gy ⫽ 25 ⫻ 103/mm3) for the amifostine-treated patients and 295 ⫻ 103/mm3 (delta ⬍10
Differential cell counts For differential cell counts available (n ⫽ 132), values of neutrophil granulocytes and lymphocytes for both treatment groups were related to the radiation dose (Fig. 3). No difference was observed between amifostine-treated and control patients for the decline in lymphocytes (both groups: ⫺21 lymphocytes/mm3/Gy). However, neutrophil granulo-
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● Biology ● Physics
Volume 51, Number 4, 2001
Fig. 3. Lymphocyte counts and neutrophil granulocyte counts at a given dose are depicted (filled circles at left, amifostine; open circles at right, controls). Linear regression lines are shown.
cytes seemed to increase during radiotherapy of amifostinetreated patients (⫹10 neutrophil granulocytes/mm3/Gy); in contrast, control patients showed a decline (⫺18 neutrophil granulocytes/mm3/Gy) (Fig. 3).
DISCUSSION As well as technical developments, a pharmacologic modulation of radiosensitivity is expected to increasingly influence modern radiotherapy. Thus, radioprotection may not only provide a better quality of life for patients, but eventually allow an increase in radiation dose and improvement in cure rate. Amifostine, a scavenger of radiationinduced free radicals, is one of the most intensively studied radioprotectors (1–12). It is known to protect parotidea and small salivary glands from radiation injuries (17–22). Particularly, the occurrence of acute and chronic radiation xerostomia can be effectively diminished (16); as a consequence, dental health will be retained (10). Though the hematotoxicity of total body irradiation cannot be prevented (23), patients undergoing half-body irradiation experience an improved hematopoiesis when treated with amifostine (5). Wondering whether the hematopoietic radioprotection might help to better understand the mechanism of amifostine’s activity, we undertook the investigation of hemato-
logic parameters pertaining to patients given small volumes of radiation. Our results clearly demonstrate that even a 60 Gy irradiation of small volumes, as applied to patients with headand-neck cancer, decreases leukocytes from 8.1 ⫻ 103/mm3 to 5.8 ⫻ 103/mm3, as well as platelets from 318 ⫻ 103/mm3 to 270 ⫻ 103/mm3; the blood hemoglobin concentration, on the other hand, essentially persists during the radiotherapy course (13.5 g/dL). The platelet count is not affected by amifostine. However, amifostine treatment will counteract the decline in the number of leukocytes (7.5 ⫻ 103/mm3 to 7.0 ⫻ 103/mm3). This is caused by an increase in the absolute amount of neutrophil granulocytes. The radiation-induced decrease in lymphocytes is not affected by amifostine (Fig. 3). The prevention of leukocytopenia by amifostine is statistically significant when analyzed with a two-tailed t test (p ⬍ 0.005). Though a difference of dose per week between amifostine patients and control patients cannot definitely be ruled out, it seems unlikely: The dose densities (Gy per week) for both amifostine and control patients are comparable (Fig. 1). Furthermore, data on additional populations from other institutions confirm our previous observation (15).
Alteration of radiation-induced hematotoxicity by amifostine
We did not investigate the mechanism of amifostine’s selective radioprotective activity on the granulopoiesis. A difference in radiosensitivity among different cell lines may be causative. A more likely cause is the difference in enzyme patterns among blood cells. Myelopoietic cells are known to express alkaline phosphatase (24). This enzyme is essential for the uptake and metabolism (6) of amifostine, to finally enable its radioprotective potential. It is of note that neutrophil granulocytes are nondividing cells. Thus, radiation-induced granulocytopenia must be the consequence of irradiating specific circulating myelopoietic stem cells. Because amifostine does
● F. MOMM et al.
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not affect the decrease in platelet count after radiotherapy, we speculate that thrombopoietic stem cells tend to circulate less often in the peripheral blood. Clearly, in patients undergoing radiotherapy, the mechanism of amifostine’s activity on granulopoiesis needs further investigation to broaden our knowledge and eventually guide us toward the drug’s use in protecting other tissues, as well. We conclude that amifostine protects the hematopoiesis from radiation injury, particularly the neutrophil granulopoietic lineage. The underlying mechanism may be related to cellular enzymes and should be further studied.
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