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Preparation of [131I]lipiodol as a hepatoma therapeutic agent
Appl. Radial. Isot. Vol. 43, No. 12, pp. 1431-1435, ht. J. Radiat. Appl. Instrum. Part A
0883-2889/92
1992
$5.00 + 0.00
Copyright 0 I992 Pergamon Press Ltd
Printed in Great Britain. AI1rights reserved
Preparation
JIUNN-GUANG
of [‘311]Lipiodol as a Hepatoma Therapeutic Agent LO’, AI-YIH WANG’, YUAN-YAW WEI], WING-YIU CHIN-WEN CHI* and WING-KAI CHAN3
LUI*,
‘Institute of Nuclear Science, National Tsing Hua University, Hsinchu, Taiwan, Republic of China, ‘Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China and “Institute of Biomedical Sciences, Academia Sinica, Taipei, Republic of China (Received 18 May 1992; in revised form 8 July 1992) An isotopic exchange method was used to label lipiodol with ‘s’I. The labelling efficiency was > 92.5%, and the radiochemical purity of [‘3’I]lipiodol was above 98% as determined by ITLC. The influencing factors e.g. the heating temperature, reaction time, pH and storage conditions were studied and the optimum conditions were determined. In a pilot study injecting [‘3’I]lipiodol for the treatment of hepatoma, about 70% of hepatoma patients had a response to the treatment with a reduction of a-fetoprotein and decrease of hepatoma sizes. The overall median survival was 9 months (range 2-17 months).
Introduction is the most common cancer in males and the third most common cancer in females in Taiwan (Anonymous, 1984). Its prognosis is extremely poor unless the tumor was diagnosed in an early stage and resected before metastasis. Nakakuma et al. (1979) injected an oily contrast Hepatoma
material through the hepatic artery used for lymphangiograms and confirmed selective retention of the reagent in tumor. The iodized oil conjoint with an anticancer reagent has been utilized in a therapeutic feasibility study for hepatoma (Nakakuma et al., 1983; Ohishi et al., 1985; Kannemastsu et al., 1984; Konno et al., 1983; Iwai et al., 1984; Fukushima et al., 1987). Lipiodol is a contrast
medium consisting of an ethylester of the fatty acid of linseed oil, which remains in hepatomas much longer than in the normal tissues when injected (Idezuki et al., 1966). Deposits of lipiodol have been detected in hepatoma for as long as 1 year. Iodine is the major component in lipiodol (about 40%), and 13’1was an effective agent for thyroid cancer therapy. Using an isotopic exchange to replace the iodine in lipiodol with “‘I, this compound may then be used as a radiotherapeutic agent targeted specifically to hepatoma. This will deliver a very high radiation dosage to the tumor but minimal dosage to the adjacent normal tissue. There are reports (Raol et al., 1986; Kobayashi et al., 1984, 1985) describing the use of [‘3’I]lipiodol to assess the possibility of transcatheter internal
radiotherapy of hepatic cancer. Kobayashi et al. (1985), investigated 5 patients with hepatoma, and found that there were similar variations of [‘3’I]lipiodol biodistribution. The radioactive ratio of lung to liver was from 0.1 to 0.4, and the ratio did not significantly change with time in the individual case. At the same time the activity ratio of hepatoma to normal tissue ranged 3-8. Therefore, making use of [‘311]lipiodol for hepatoma therapy is worth investigating. The purpose of this study was to determine the optimum conditions for the preparation of [“‘I]lipiodol by analyzing the effects of heating procedure, pH change and storage conditions. Some pilot studies of injection [‘3’I]lipiodol for the treatment of hepatoma are discussed in this report, too.
Experimental Chemical reagents
Lipiodol was obtained from Laboratoire Guerbet, Paris, France. Sodium iodide (13’1),dissolved in 0.5% NaHCO, solution with a pH of 9, was produced in the Division of Radioisotope of the National Tsing Hua University. All other reagents were purchased from Merck. Experiments Original method for the preparation of [‘3’I]lipiodol.
The [‘3’I]lipiodol was obtained by isotope exchange reaction of ionic “‘I and organic iodine. The labelling
1431
1432
JIUNN-GUANG Lo et al. Table I. The analysis of [“‘I]lipiodol* “‘I activity (mCi) Predry 12.0 30.0 63.5 230.0 239.3 113.3
pH of lipiodol
Postlabel (LEf%)
Postfiltration (recovery yield%)
II.0 (91.6) 27.1 (90.3) 56.1 (89.3) 188.3 (81.9) 214 (89.4) 109.6 (96.7)
(66.7) 20.0 (66.71 ‘44.8’ (70.5) 128.1 (55.7) 141.7 (59.2) 101.2 (89.3)
8.0
RPt %
Prelabel Postlabel (Approximate)
99.1
5.2
5.0
97.6
5.0
4.8
99.4
4.8
5.0
100
5.0
5.0
100
5.2
5.0
5.0
5.0
97.2
*[“‘I]Lipiodol was labelled by original method. tRP. Radiochemical uuritv. ’ radioactivity of postlabel [“‘I]lipiodol SLE, Labelling efficiency = radioactivity of predry
procedure was described as follows: Na13’I was mixed with 1 mL ethanol in a 25 mL round bottom flask. The mixture was dried under conditions of stirring in a 45°C oil bath of PEG400 (polyethylene glycol 400) and purged by nitrogen. The dried mixture was dissolved in 1 mL ethanol again, and treated with 2-5 mL lipiodol. After being heated at 80°C for 20min to remove the ethanol, the mixture was continuously heated at 100°C for 30 min to improve the labelling efficiency. Radiochemical purity, required to be not less than 95% of labelled compound, was assayed by ITLC (Instant Thin Layer Chromatography T”SG, Gelman) in 85% methanol. The end product was sterilized by 0.2 pm membrane filtration, and adjusted to the desired radiochemical concentration with unlabelled lipiodol. Modification of the labelling condition of [“‘I]lipiodol. To shorten the drying time, the drying
temperature was raised to 80°C to instead of 45”C, the effects of the drying rate of ethanol and vaporization of 13’1were also considered. On the other hand, the various reaction times and heating temperature (1OoOC for 10min; 80°C for 20 or 40min; 60°C for 60 min) were chosen to evaluate the labelling efficiency and radiochemical purity of [“‘I]lipiodol. The “*I is more stable in basic solution than in acid solution, the pH of Na13’1 solution was adjusted to 8, 9, 10 and 12 by adding borate buffer or 0.45% NaOH-ethanol solution to test the effect of pH on the 13’1loss during the heating processes. The [‘3’I]lipiodol were stored in the dark or light at room temperature and at 2-8°C to evaluate the Table 2. Effects of drying conditions on the loss of “‘I Temperature (“C) 45 45 80 80
Ethanol
Drying rate ( x 10’ mL/min)
NO Yes NO Yes
2.63kO.17 3.12 _+0.43 6.13 f 1.41 8.19 f 1.91
lRFI, Residual fraction of “‘1 is defined by: RF1 = radioactivity of postdry (or prelabel) 13’1 radioactivity of predry “‘I
RFI’ (%) 9.98 98.3 91.2 96.5
+ 1.7 i 1.4 i 2.7 f 4.3
stability of [‘3’I]lipiodol. The stability was evaluated by radiochemical purity, appearance and pH over 4 weeks. Quality analysis of [‘3’I]lipiodol. The radioactivity was measured by curiemeter (Capintec CRCS) of each treatment stage. When labelled compound was produced, the quality of [“‘IJlipiodol was analyzed by ITLC in 85% methanol to determinate the radiochemical purity, and the radioactivity measured by NaI(T1) detector (Canberra). The functional group of [‘3’I]lipiodol was determinate with an i.r. spectrophotometer (Jascd A-100), and the pH was measured with a pH test paper (ToYo). Pilot study of [“‘I]lipiodol for the treatment of hepatoma. Ten patients were selected to do the pilot
study, and the selected criteria, treatment method, biodistribution and dosage calculation were mentioned in a previous report (Lui et al., 1990).
Results Table 1 showed the results of labelling analysis of [‘3’I]lipiodol. The radiochemical purity of [‘311]lipiodol was not less than 97.2%. The labelling efficiency ranged from 81.9 to 96.7%, after filtration the recovery yield from 55.7 to 89.3%. The pH of [‘3’I]lipiodol was similar to lipiodol, it seems the labelling process did not change the pH value, even the labelling was carried out in the alkaline solution of sodium iodide with pH 9. Table 2 shows the effect of drying conditions on the loss of 13’I. No matter whether ethanol was present in Na13’I solution or not, the drying rates at 80°C were about 2.5 times as fast Table 3. Effects of labelling conditions on the labelling efficiency of radiochemical purity Reaction temperature (“C) Group Group Group Group
A B C D
100 80 80 60
Reaction time (min)
Labelling efficiency (%)
Radiochemical purity (%)
IO 20 40 60
92.5 + 0.7 92.4 & 0.9 91.5 * 3.9 87.2 + 2.8
98.2 i 2.5 93.6 +_9.1 98.6 f I.2 91.6 + 4.0
Preparation of [“‘I]lipiodol Table 4. The analysis
of [“‘I]lipiodol
Predry PH 12 IO 9 8 12 IO 9 8 NaOH*,
Adiust
bv
Borate Borate Borate Borate NaOH* NaOH* NaOH* NaOH*
1433
proceeds at various
Prelabel Activity
(tiCi)
531 540 435 535 305 326 319 307
pH
Postlabel
PH
RF1 (%)
PH
LE (%)
RP (%)
Aooearance
7.0 7.0 6.0 6.0 10.0 9.0 8.0 1.5
97.7 96.3 99.1 92.9 97.5 98.8 97.0 98.4
.70 7.0 5.0 5.0 8.5 7.5 7.0 6.0
92.3 91.3 94.9 90.8 91.8 93.6 90.1 91.6
99.2 99.5 100 100 97.0 96.2 98.8 98.3
Oily liquid Oily liquid Oily liquid Oily liquid Gelling Foaming Oily liquid Oily liquid
0.45% NaOH-ethanol
as at 45°C. The solution with ethanol dried faster than the solution without ethanol both at 45°C and 8O”C, but the total drying time showed no significant difference. Anyhow, the residual fraction activity of 13’1remained 96.5-98% after drying; i.e. there was little loss of 13’1during the drying process. The effects of labelling condition on the labelling efficiency and radiochemical purity are shown in Table 3. There was no significant difference in group B and C, this means that when the reaction temperature was 8O”C, the isotope exchange reaction was almost complete within 20 min, therefore on prolonging the reaction time to 40 min the labelling efficiency was not significantly changed. The isotope exchange ratio will increase with increasing the reaction temperature. When the reaction temperature was increased to 100°C the ratio of isotope exchange will saturate within 10 min.
?,
There was no great change of labelling efficiency and radiochemical purity with processing at different pH values adjusted by borate buffer or 0.45% NaOH-ethanol (Table 4). Both of labelling efficiency and radiochemical purity are high, but the appearance of [‘3’I]lipiodol will change with different reaction conditions. The [‘3’I]lipiodol gelling or foaming if the pH of Na13’I solution was adjusted to 10 and 12 by 0.45% NaOH-ethanol. The i.r. spectra of lipiodol and [‘3’I]lipiodol are shown in Fig. 1. There was no significant difference between the two i.r. spectra, i.e., the introduction of 13’1into lipiodol was a simple isotope exchange, and the labelling process did not change the chemical structure of lipiodol. The [‘3’I]lipiodol was stable at least up to one month at 4°C (Table 5). Table 6 shows the dosage and biodistribution of [‘3’I]lipiodol in hepatoma patients. The average
[t3’I]Lipiodol
I-
c-o c-o
stretch
stretch C-H stretch
L 4000
3000
2000
1500
Wave Fig. 1. The i.r. spectra
number
(cm-‘)
of lipiodol
and [‘311]lipiodol.
1000
500
1434
JIUNN-GUANG Lo et al. Table 5. Stability analysis of [“‘IJlipiodol under different storage conditions over 28 days Day after label
Condition Light
Temperature
Analysis
0
1
14
21
28
No
Room
Yes
Room
No
Cold
RP (%) PH Color RP (%) PH Color RP (%) PH Color
99.8 5.0 Y* 99.8 5.0 Y* 99.5 5.0 Y’
99.6 4.8 Y 99.5 5.0 Y 99.2 5.0 Y
99.5 5.0 Y 99.3 5.0 Y 99.1 5.0 Y
99.2 5.0 Y 99.5 5.0 Y 99.0 5.0 Y
99.0 5.0 Brown 99.0 5.0 Brown 99.5 5.0 Y
Y*, Light yellow. Table 6. The dosage and biodistribution “‘I Case
(mCi)
1 2 3 4
14.9 15.3 34.5 16.5 23.3 28.6 23.1 41.4 12.0 25.6 30.0 63.0 53.7
5 6 7 8 9 10
(days)
Total tumor irradiation (GYs)
4.58 4.98 6.80 5.65
350 520 520 600
5.5 1.8 6.8 9.0
48 15 30 46
99.6 91.1 118.5
3.70 8.13
440 980
8.4 8.2
34 31
12.0 25.6 168.1
4.19 5.10 4.17
140 240 880
5.2 2.7 4.4
30 61 44
97.1
6.20
520
5.6
33
Injection total 11,2 dose (mCi) 43.0 19.0 37.5 19.8 40.9 62.5 44.0
31.1 44.0 44.0
of [‘311]lipiodol in hepatoma patients
57.9 34.3 72.0
dosage of [‘“I]lipiodol was 23.1 + 7.9 mCi; the total tumor dose was 181 + 60 Gy for single treatment. The radiation dose ratio of tumor to liver was 6.1 + 2.4. Table 7 shows the response of hepatoma patients to [r3’I]lipiodol treatment. Seventy percent of patients had decreased a-fetoprotein and 60% patients decreased the hepatoma size (from 22% to 64%) after [“‘I]lipiodol treatment. Three patients had partial response with reduction in tumor size of 52, 64, and 57%. The tumor size of one patient was unable to be determined due to undefined tumor margin in the CT scan. Median survival of 10 patients in the study was 9 months (from 2 to 17 months). There were no vomiting, liver pain, nausea, etc., side effects during or after therapeutic course, but the WBC averaged decreased 20%. No patient died of treatment related side effect.
Lung irradiation (%)
Hepatoma/liver radiation
Discussion The isotope exchange ratio can be controlled by changing reaction time and temperature. In the optimum conditions (lOOC, 10 min), the labelling efficiency (92.5%) and radiochemical purity (98.2%) were satisfactory. However, the product showed foaming or slight gelation when the end product was maintained alkaline. The [“‘I]lipiodol may be saponified under the higher pH values. In the process of adjusting pH values of sodium iodide solution, the best choice was borate buffer, because the pH of the end product ([‘3’I]lipiodol) was either acid or neutral. The i.r. spectra show the labelling course didn’t change the chemical structure of lipiodol. The lipiodol becomes brown due to the release of iodine if it is exposed to air and light (Gennaro et al.,
Table 7. Resoonse of heoatoma oatients to I”‘Illiaiodol treatment Case
Tumor volume*
Survival
WBC (lowest count)
Initial (cm’)
Reduction (%)
Status
Period
1380 4400 4660 2600 1500 2300 3600 3600 2060 3800
53 U 393 204 I747 601 691 21 60 17
52 U 64 57 22 48 P P 42 P
Alive Alive Died Died Died Died Died Died Died Alive
17 months 16 months IO months 9 months 4 months 11 months 2 months 3 months 9 months 8 months
*Tumor volume was measured by computerized tomograph pixels. U, Undefined tumor margin. P, Progression of tumor.
Preparation of [‘r’I]lipiodol
1985). [‘3’I]Lipiodol did not change in color within 3 weeks whether stored at room or cold temperature. It became brown after 4 weeks storage in room temperature, but the color of [‘3’I]lipiodol was yellow if stored in the cold (4°C) temperature. This means that the [‘3’I]lipiodol was stable at least up to one month at 4°C. The maximal tolerated external irradiation is 30 Gy for liver (Ingold et al., 1965). In our study a calculated radiation dosage of 260 Gy can be delivered to the hepatoma so the used [“‘I]lipiodol to deliver an internal irradiation source specifically to tumor not only increased the local irradiation dosage but also reduced the unnecessary irradiation of normal tissues. In conclusion, the data from this pilot study indicate that [‘3’I]lipiodol treatment is simple, safe, inexpensive, effective and non-toxic. The preliminary results are instructive and encouraging.
References Anonymous (1984) Health Statistic of the Republic of China II, -Vital S;atist& pp 40-58. _ _ _ Fukushima S.. Kawaauchi T. and Nishida M. (1987) Selective anticancer effects of 3’,5’-dioctanoly-S-flu&o-2’: deoxyuridine, a lipophilic prodrug of 5-fluoro-2’deoxyuridine, dissolved in an oily lymphographic agent on hepatic cancer of rabbits bearing VX-2 tumor. Cancer Res. 47, 1930.
Gennaro A. R. (1985) Remington’s Pharmaceutical Science, 17th edn, p. 1267. Merck, Pennsylvania. Idexuki Y., Sugiura M. and Hatano S. (1966) Hepatography for detection of small tumor masses in liver: experiences with oily contrast medium. Surgery 60, 566. Ingold J. A., Reed G. B. and Kaplom H. S. (1965) Radiation hepatitis. Am. J. Radio/. 93, 200.
1435
Iwai K., Maeda H. and Konno T. (1984) Use of oily contrast medium for selective drug trapping to tumor: enhanced therapeutic effect and X-ray image. Cancer Res. 44,211s.
Kannemastsu T., Inokuchi K. and Sugimachi K. (1984) Selective effects of lipiodolixed antitumor agents. J. Surg. Oncol. 25, 182. Kobayashi H., Nakajo M., Shimaburo K., Shirono K., Sakata H., Oyama T. and Sonoda T. (1984) Possibility of radiotherapy of hepatic cancer by transcatheter arterial embolization with radioactive lipiodol. Nipp. Act. Radio. 45, 1176. Kobayashi H., Nakajo M., Yano T., Shimaburo K. and Shinohara S. (1985) Transcatheter internal radiotherapy of hepatoma using radioactivity oidized oil (‘3’I-lipiodol). Nipp. Act. Radio. 45, 1176.
Konno T., Mudea H., Iwai K., Tashiro S., Maki S. Morinaga T., Mochinaga M., Hiraoka T. and Yokoyama I. (1983) Effects of arterial administration of hiah molecular weight anticancer agents SMANCS with lip:d lymphographic agent on hepatoma: a preliminary report. Eur. J. Cancer Clinl. Oncol. 19, 1053. Lui W. Y., Lui R. S., Chang J. H., Lo J. G., Lai K. H., Wei Y. Y.. Chi C. W. and Chan W. K. (1990) Report of a nilot study. of intraarterial injection of I-131 lipiodol for the treatment of hepatoma. Chin. Med. J. 46, 125. Nakakuma K., Tashiro S. and Uemura K. (1979) An attempt for increasing effects of hepatic artery ligation for advanced henatoma. Jpn Deutsche. Med. Beriehte. (1979) 24, 675.
-
_
Nanakuma K., Tashiro T., Hiraoka T., Uemura K., Kono T., Miyauchi Y. and Yokoyama (1983) Studies on anticancer treatment with an oily anticancer drug injected into the ligated feeding hepatic artery for cancer. Cancer 52, 2193. Ohishi H., Uohida H., Ohue S., Ueda J., Katsuragi M., Matsuo N. and Yoshimura H. (1985) Hepatocellular carcinoma detected by iodized oil. Radiology 154, 25. Raol J. L., Duranferrier R. and Bourguet P. (1986) Angiography with I-13 1ethiodol labelled iodized oil in malignant hepatoma. J. Radiol. 67, 797.
0883-2889/92
1992
$5.00 + 0.00
Copyright 0 I992 Pergamon Press Ltd
Printed in Great Britain. AI1rights reserved
Preparation
JIUNN-GUANG
of [‘311]Lipiodol as a Hepatoma Therapeutic Agent LO’, AI-YIH WANG’, YUAN-YAW WEI], WING-YIU CHIN-WEN CHI* and WING-KAI CHAN3
LUI*,
‘Institute of Nuclear Science, National Tsing Hua University, Hsinchu, Taiwan, Republic of China, ‘Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China and “Institute of Biomedical Sciences, Academia Sinica, Taipei, Republic of China (Received 18 May 1992; in revised form 8 July 1992) An isotopic exchange method was used to label lipiodol with ‘s’I. The labelling efficiency was > 92.5%, and the radiochemical purity of [‘3’I]lipiodol was above 98% as determined by ITLC. The influencing factors e.g. the heating temperature, reaction time, pH and storage conditions were studied and the optimum conditions were determined. In a pilot study injecting [‘3’I]lipiodol for the treatment of hepatoma, about 70% of hepatoma patients had a response to the treatment with a reduction of a-fetoprotein and decrease of hepatoma sizes. The overall median survival was 9 months (range 2-17 months).
Introduction is the most common cancer in males and the third most common cancer in females in Taiwan (Anonymous, 1984). Its prognosis is extremely poor unless the tumor was diagnosed in an early stage and resected before metastasis. Nakakuma et al. (1979) injected an oily contrast Hepatoma
material through the hepatic artery used for lymphangiograms and confirmed selective retention of the reagent in tumor. The iodized oil conjoint with an anticancer reagent has been utilized in a therapeutic feasibility study for hepatoma (Nakakuma et al., 1983; Ohishi et al., 1985; Kannemastsu et al., 1984; Konno et al., 1983; Iwai et al., 1984; Fukushima et al., 1987). Lipiodol is a contrast
medium consisting of an ethylester of the fatty acid of linseed oil, which remains in hepatomas much longer than in the normal tissues when injected (Idezuki et al., 1966). Deposits of lipiodol have been detected in hepatoma for as long as 1 year. Iodine is the major component in lipiodol (about 40%), and 13’1was an effective agent for thyroid cancer therapy. Using an isotopic exchange to replace the iodine in lipiodol with “‘I, this compound may then be used as a radiotherapeutic agent targeted specifically to hepatoma. This will deliver a very high radiation dosage to the tumor but minimal dosage to the adjacent normal tissue. There are reports (Raol et al., 1986; Kobayashi et al., 1984, 1985) describing the use of [‘3’I]lipiodol to assess the possibility of transcatheter internal
radiotherapy of hepatic cancer. Kobayashi et al. (1985), investigated 5 patients with hepatoma, and found that there were similar variations of [‘3’I]lipiodol biodistribution. The radioactive ratio of lung to liver was from 0.1 to 0.4, and the ratio did not significantly change with time in the individual case. At the same time the activity ratio of hepatoma to normal tissue ranged 3-8. Therefore, making use of [‘311]lipiodol for hepatoma therapy is worth investigating. The purpose of this study was to determine the optimum conditions for the preparation of [“‘I]lipiodol by analyzing the effects of heating procedure, pH change and storage conditions. Some pilot studies of injection [‘3’I]lipiodol for the treatment of hepatoma are discussed in this report, too.
Experimental Chemical reagents
Lipiodol was obtained from Laboratoire Guerbet, Paris, France. Sodium iodide (13’1),dissolved in 0.5% NaHCO, solution with a pH of 9, was produced in the Division of Radioisotope of the National Tsing Hua University. All other reagents were purchased from Merck. Experiments Original method for the preparation of [‘3’I]lipiodol.
The [‘3’I]lipiodol was obtained by isotope exchange reaction of ionic “‘I and organic iodine. The labelling
1431
1432
JIUNN-GUANG Lo et al. Table I. The analysis of [“‘I]lipiodol* “‘I activity (mCi) Predry 12.0 30.0 63.5 230.0 239.3 113.3
pH of lipiodol
Postlabel (LEf%)
Postfiltration (recovery yield%)
II.0 (91.6) 27.1 (90.3) 56.1 (89.3) 188.3 (81.9) 214 (89.4) 109.6 (96.7)
(66.7) 20.0 (66.71 ‘44.8’ (70.5) 128.1 (55.7) 141.7 (59.2) 101.2 (89.3)
8.0
RPt %
Prelabel Postlabel (Approximate)
99.1
5.2
5.0
97.6
5.0
4.8
99.4
4.8
5.0
100
5.0
5.0
100
5.2
5.0
5.0
5.0
97.2
*[“‘I]Lipiodol was labelled by original method. tRP. Radiochemical uuritv. ’ radioactivity of postlabel [“‘I]lipiodol SLE, Labelling efficiency = radioactivity of predry
procedure was described as follows: Na13’I was mixed with 1 mL ethanol in a 25 mL round bottom flask. The mixture was dried under conditions of stirring in a 45°C oil bath of PEG400 (polyethylene glycol 400) and purged by nitrogen. The dried mixture was dissolved in 1 mL ethanol again, and treated with 2-5 mL lipiodol. After being heated at 80°C for 20min to remove the ethanol, the mixture was continuously heated at 100°C for 30 min to improve the labelling efficiency. Radiochemical purity, required to be not less than 95% of labelled compound, was assayed by ITLC (Instant Thin Layer Chromatography T”SG, Gelman) in 85% methanol. The end product was sterilized by 0.2 pm membrane filtration, and adjusted to the desired radiochemical concentration with unlabelled lipiodol. Modification of the labelling condition of [“‘I]lipiodol. To shorten the drying time, the drying
temperature was raised to 80°C to instead of 45”C, the effects of the drying rate of ethanol and vaporization of 13’1were also considered. On the other hand, the various reaction times and heating temperature (1OoOC for 10min; 80°C for 20 or 40min; 60°C for 60 min) were chosen to evaluate the labelling efficiency and radiochemical purity of [“‘I]lipiodol. The “*I is more stable in basic solution than in acid solution, the pH of Na13’1 solution was adjusted to 8, 9, 10 and 12 by adding borate buffer or 0.45% NaOH-ethanol solution to test the effect of pH on the 13’1loss during the heating processes. The [‘3’I]lipiodol were stored in the dark or light at room temperature and at 2-8°C to evaluate the Table 2. Effects of drying conditions on the loss of “‘I Temperature (“C) 45 45 80 80
Ethanol
Drying rate ( x 10’ mL/min)
NO Yes NO Yes
2.63kO.17 3.12 _+0.43 6.13 f 1.41 8.19 f 1.91
lRFI, Residual fraction of “‘1 is defined by: RF1 = radioactivity of postdry (or prelabel) 13’1 radioactivity of predry “‘I
RFI’ (%) 9.98 98.3 91.2 96.5
+ 1.7 i 1.4 i 2.7 f 4.3
stability of [‘3’I]lipiodol. The stability was evaluated by radiochemical purity, appearance and pH over 4 weeks. Quality analysis of [‘3’I]lipiodol. The radioactivity was measured by curiemeter (Capintec CRCS) of each treatment stage. When labelled compound was produced, the quality of [“‘IJlipiodol was analyzed by ITLC in 85% methanol to determinate the radiochemical purity, and the radioactivity measured by NaI(T1) detector (Canberra). The functional group of [‘3’I]lipiodol was determinate with an i.r. spectrophotometer (Jascd A-100), and the pH was measured with a pH test paper (ToYo). Pilot study of [“‘I]lipiodol for the treatment of hepatoma. Ten patients were selected to do the pilot
study, and the selected criteria, treatment method, biodistribution and dosage calculation were mentioned in a previous report (Lui et al., 1990).
Results Table 1 showed the results of labelling analysis of [‘3’I]lipiodol. The radiochemical purity of [‘311]lipiodol was not less than 97.2%. The labelling efficiency ranged from 81.9 to 96.7%, after filtration the recovery yield from 55.7 to 89.3%. The pH of [‘3’I]lipiodol was similar to lipiodol, it seems the labelling process did not change the pH value, even the labelling was carried out in the alkaline solution of sodium iodide with pH 9. Table 2 shows the effect of drying conditions on the loss of 13’I. No matter whether ethanol was present in Na13’I solution or not, the drying rates at 80°C were about 2.5 times as fast Table 3. Effects of labelling conditions on the labelling efficiency of radiochemical purity Reaction temperature (“C) Group Group Group Group
A B C D
100 80 80 60
Reaction time (min)
Labelling efficiency (%)
Radiochemical purity (%)
IO 20 40 60
92.5 + 0.7 92.4 & 0.9 91.5 * 3.9 87.2 + 2.8
98.2 i 2.5 93.6 +_9.1 98.6 f I.2 91.6 + 4.0
Preparation of [“‘I]lipiodol Table 4. The analysis
of [“‘I]lipiodol
Predry PH 12 IO 9 8 12 IO 9 8 NaOH*,
Adiust
bv
Borate Borate Borate Borate NaOH* NaOH* NaOH* NaOH*
1433
proceeds at various
Prelabel Activity
(tiCi)
531 540 435 535 305 326 319 307
pH
Postlabel
PH
RF1 (%)
PH
LE (%)
RP (%)
Aooearance
7.0 7.0 6.0 6.0 10.0 9.0 8.0 1.5
97.7 96.3 99.1 92.9 97.5 98.8 97.0 98.4
.70 7.0 5.0 5.0 8.5 7.5 7.0 6.0
92.3 91.3 94.9 90.8 91.8 93.6 90.1 91.6
99.2 99.5 100 100 97.0 96.2 98.8 98.3
Oily liquid Oily liquid Oily liquid Oily liquid Gelling Foaming Oily liquid Oily liquid
0.45% NaOH-ethanol
as at 45°C. The solution with ethanol dried faster than the solution without ethanol both at 45°C and 8O”C, but the total drying time showed no significant difference. Anyhow, the residual fraction activity of 13’1remained 96.5-98% after drying; i.e. there was little loss of 13’1during the drying process. The effects of labelling condition on the labelling efficiency and radiochemical purity are shown in Table 3. There was no significant difference in group B and C, this means that when the reaction temperature was 8O”C, the isotope exchange reaction was almost complete within 20 min, therefore on prolonging the reaction time to 40 min the labelling efficiency was not significantly changed. The isotope exchange ratio will increase with increasing the reaction temperature. When the reaction temperature was increased to 100°C the ratio of isotope exchange will saturate within 10 min.
?,
There was no great change of labelling efficiency and radiochemical purity with processing at different pH values adjusted by borate buffer or 0.45% NaOH-ethanol (Table 4). Both of labelling efficiency and radiochemical purity are high, but the appearance of [‘3’I]lipiodol will change with different reaction conditions. The [‘3’I]lipiodol gelling or foaming if the pH of Na13’I solution was adjusted to 10 and 12 by 0.45% NaOH-ethanol. The i.r. spectra of lipiodol and [‘3’I]lipiodol are shown in Fig. 1. There was no significant difference between the two i.r. spectra, i.e., the introduction of 13’1into lipiodol was a simple isotope exchange, and the labelling process did not change the chemical structure of lipiodol. The [‘3’I]lipiodol was stable at least up to one month at 4°C (Table 5). Table 6 shows the dosage and biodistribution of [‘3’I]lipiodol in hepatoma patients. The average
[t3’I]Lipiodol
I-
c-o c-o
stretch
stretch C-H stretch
L 4000
3000
2000
1500
Wave Fig. 1. The i.r. spectra
number
(cm-‘)
of lipiodol
and [‘311]lipiodol.
1000
500
1434
JIUNN-GUANG Lo et al. Table 5. Stability analysis of [“‘IJlipiodol under different storage conditions over 28 days Day after label
Condition Light
Temperature
Analysis
0
1
14
21
28
No
Room
Yes
Room
No
Cold
RP (%) PH Color RP (%) PH Color RP (%) PH Color
99.8 5.0 Y* 99.8 5.0 Y* 99.5 5.0 Y’
99.6 4.8 Y 99.5 5.0 Y 99.2 5.0 Y
99.5 5.0 Y 99.3 5.0 Y 99.1 5.0 Y
99.2 5.0 Y 99.5 5.0 Y 99.0 5.0 Y
99.0 5.0 Brown 99.0 5.0 Brown 99.5 5.0 Y
Y*, Light yellow. Table 6. The dosage and biodistribution “‘I Case
(mCi)
1 2 3 4
14.9 15.3 34.5 16.5 23.3 28.6 23.1 41.4 12.0 25.6 30.0 63.0 53.7
5 6 7 8 9 10
(days)
Total tumor irradiation (GYs)
4.58 4.98 6.80 5.65
350 520 520 600
5.5 1.8 6.8 9.0
48 15 30 46
99.6 91.1 118.5
3.70 8.13
440 980
8.4 8.2
34 31
12.0 25.6 168.1
4.19 5.10 4.17
140 240 880
5.2 2.7 4.4
30 61 44
97.1
6.20
520
5.6
33
Injection total 11,2 dose (mCi) 43.0 19.0 37.5 19.8 40.9 62.5 44.0
31.1 44.0 44.0
of [‘311]lipiodol in hepatoma patients
57.9 34.3 72.0
dosage of [‘“I]lipiodol was 23.1 + 7.9 mCi; the total tumor dose was 181 + 60 Gy for single treatment. The radiation dose ratio of tumor to liver was 6.1 + 2.4. Table 7 shows the response of hepatoma patients to [r3’I]lipiodol treatment. Seventy percent of patients had decreased a-fetoprotein and 60% patients decreased the hepatoma size (from 22% to 64%) after [“‘I]lipiodol treatment. Three patients had partial response with reduction in tumor size of 52, 64, and 57%. The tumor size of one patient was unable to be determined due to undefined tumor margin in the CT scan. Median survival of 10 patients in the study was 9 months (from 2 to 17 months). There were no vomiting, liver pain, nausea, etc., side effects during or after therapeutic course, but the WBC averaged decreased 20%. No patient died of treatment related side effect.
Lung irradiation (%)
Hepatoma/liver radiation
Discussion The isotope exchange ratio can be controlled by changing reaction time and temperature. In the optimum conditions (lOOC, 10 min), the labelling efficiency (92.5%) and radiochemical purity (98.2%) were satisfactory. However, the product showed foaming or slight gelation when the end product was maintained alkaline. The [“‘I]lipiodol may be saponified under the higher pH values. In the process of adjusting pH values of sodium iodide solution, the best choice was borate buffer, because the pH of the end product ([‘3’I]lipiodol) was either acid or neutral. The i.r. spectra show the labelling course didn’t change the chemical structure of lipiodol. The lipiodol becomes brown due to the release of iodine if it is exposed to air and light (Gennaro et al.,
Table 7. Resoonse of heoatoma oatients to I”‘Illiaiodol treatment Case
Tumor volume*
Survival
WBC (lowest count)
Initial (cm’)
Reduction (%)
Status
Period
1380 4400 4660 2600 1500 2300 3600 3600 2060 3800
53 U 393 204 I747 601 691 21 60 17
52 U 64 57 22 48 P P 42 P
Alive Alive Died Died Died Died Died Died Died Alive
17 months 16 months IO months 9 months 4 months 11 months 2 months 3 months 9 months 8 months
*Tumor volume was measured by computerized tomograph pixels. U, Undefined tumor margin. P, Progression of tumor.
Preparation of [‘r’I]lipiodol
1985). [‘3’I]Lipiodol did not change in color within 3 weeks whether stored at room or cold temperature. It became brown after 4 weeks storage in room temperature, but the color of [‘3’I]lipiodol was yellow if stored in the cold (4°C) temperature. This means that the [‘3’I]lipiodol was stable at least up to one month at 4°C. The maximal tolerated external irradiation is 30 Gy for liver (Ingold et al., 1965). In our study a calculated radiation dosage of 260 Gy can be delivered to the hepatoma so the used [“‘I]lipiodol to deliver an internal irradiation source specifically to tumor not only increased the local irradiation dosage but also reduced the unnecessary irradiation of normal tissues. In conclusion, the data from this pilot study indicate that [‘3’I]lipiodol treatment is simple, safe, inexpensive, effective and non-toxic. The preliminary results are instructive and encouraging.
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