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Ovarian cancer: radiation sensitivity in vitro
Radiotherapy and Oncology, 19 (1990) 323-327 Elsevier
323
RADION 00786
Ovarian cancer" radiation sensitivity in vitro B. J. Slotman l, A. B. M. F. K a r i m 2 a n d B. R. Rao Department of 1Endocrinology and :Radiation Therapy, Academisch Ziekenhuis Vrije Universiteit, Amsterdam, The Netherlands (Received 27 September 1989, revision received 7 February 1990, accepted 19 June 1990)
Key words." Ovarian cancer; Radiosensitivity; In vitro
Summary The radiosensitivity of four human ovarian cancer cell lines was investigated in vitro by a clonogenic assay and analyzed using the linear-quadratic model. Two cell lines were found to be highly radiosensitive (mean inactivation dose (D) 0.82-0.92 Gy; surviving fraction 2 Gy (SF2) ~<0.13). Two other cell lines were less sensitive to radiation (D 1.31-1.94 Gy; SF 2 0.22-0.38). Although the use of external radiotherapy in ovarian cancer has been limited due to the pattern of metastatic spread of this cancer, the present data support the view that ovarian carcinomas are radiosensitive tumors. Investigations on the effects of new approaches, such as delivering radiation more specifically to intraperitoneal ovarian cancer cells, are warranted.
Introduction The role of radiation therapy in the treatment of ovarian cancer has been the subject of considerable controversy during the last decades. It has been demonstrated that pelvic irradiation is ineffective in ovarian cancer, since relapses may occur throughout the whole peritoneal cavity [3,17 ]. Whole abdominal irradiation has been used as an adjuvant to surgery [3,4,20] and as salvage therapy for patients with recurrent or persistent disease Addressfor correspondence:B. Ramanath Rao, Ph.D., Department of Endocrinology, Academisch Ziekenhuis Vrije Universiteit, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands.
following chemotherapy [ 9,10,12,13,16 ]. Little is known about the intrinsic radiosensitivity of ovarian cancer cells. We have investigated the radiosensitivity of four human ovarian cancer cell lines by in vitro cell culture techniques.
Materials and methods Cell cultures
The three established ovarian cancer cell lines (OVC NOVA, passage 190-198; OV 166, passage 31-39 and OV 1225 passage 30-37) have been initiated from tumors or ascites fluid of patients with ovarian cancer of the common epithelial type
0167-8140/90/$03.50 © 1990 Elsevier Science Publishers B.V. (Biomedical Division)
324 TABLE I Population doubling time, DNA-index (2 n = 1) and S-phase fraction (SPF) of four human ovarian cancer cell lines.
OVCNOVA OV 166 OV 1225 OV B09
Doubling time (h)
DNA-index
SPF (%)
35 30 40 150
1.7 1.1 2.0 1.6
22 24 17 16
[18,19]. The OV B09 cell line (passage 5-7) was initiated from ascitic fluid of a patient with serous adenocarcinoma of the ovary, 4 months prior to the experiments. Immunohistochemical analysis of these cell lines showed reactivity with the ovarian cancer monoclonal antibodies OC 125 and OVTL-3. Microscopically, the cell lines display epithelial cell types. The population doubling times and Sphase-fractions (SPF), determined during exponential growth phase, as well as the DNAindices of the cell lines are given in Table I. The cell cultures were maintained at 37 °C in 5 ~ CO2 in air in R P M I 1640 medium (Gibco Ltd., U.K.), supplemented with fetal calf serum (10~o v/v; Gibco Ltd., U.K.), transferrin (Sigma Chem., U.S.A.) 5/~g/ml, insulin (Novo Industry BV, Holland) 5/~g/ml, and gentamycin (Gibco Ltd., U.K.), 50 #g/ml. Since identification of distinct colonies in monolayer culture was difficult due to confluency and spreading of cells, we optioned for a semisolid agar assay. Irradiation
Immediately before irradiation, cells were trypsinised, counted using a cell counter (Sysmex Microcell counter CC-110) and pipetted into replicate tubes at concentrations of 10, 50, 100, 500 and 1000 × 103 cells/ml. The cells were irradiated using fractions of 0.5-10 Gy using a 250 kV orthovolt unit (Philips) at a dose-rate of 0.7 Gy/min. During irradiation, the cells were kept at room temperature for less than 1 h. In
preliminary experiments we found that maintaining the cells under these conditions for 1 h did not result in a decreased colony formation, as compared to cells maintained at 37 °C. After irradiation, the cell suspensions were mixed 1 : 1 with a sterile 0.5~o solution of agar (Bacto-agar, Difco, U.S.A.) in phosphate buffer saline (PB S) at 37 ° C. The mixture was layered in tissue culture wells (Tissue Culture Cluster 6, Costar, U.K.) above an underlayer of semi-solid agar mixture (1:3) of the culture medium and 0.5~o agar in PBS. The agar mixture was cooled down to room temperature and then put in an incubator (37 °C, 5 ~ CO 2 in air). Since in preliminary experiments no difference in cloning efficiency and radiation response was observed with and without the inclusion of feeder cells, in subsequent experiments no feeder cells were included. Ten days after irradiation, the number of colonies (comprising more than 50 cells) arising in agar was determined by phase-contrast microscopy. For all four cell lines, a linear relationship between the number of cells plated and the number of colonies formed was found. The cloning efficiency of the irradiated cells was calculated and compared to that of the untreated control cells. The surviving fraction was calculated by dividing the mean cloning efficiency of the irradiated cells by the cloning efficiency of the untreated control cells. In addition, we have investigated the effect of irradiation on the cell proliferation of cultures grown in liquid medium monolayer cultures. Cells in monolayer culture were irradiated in the exponential growth phase. After irradiation, the flasks were put in an incubator (37 °C, 5~o CO2 in air). Nine days after irradiation, the cells were trypsinised and counted using a cell counter. The surviving fraction was calculated by dividing the number of cells after irradiation by the number of cells in the untreated control flasks. Survival curve analysis
Survival curves were generated from at least two experiments for each cell line, according to the
325 Surviving fraction
Surviving fraction
1
0.1
0.1
0.01
0,01
0.001
0.001 2
4
6
2
8
, 4
r 6
8
Dose (Gy)
Dose (Gy)
Fig. 1. Radiation survival curve of OVC NOVA cells determined by clonogenie assay. Each point represents the mean of three replicates from different experiments.
Fig. 3. Radiation survival curve of OV 1225 cells determined by clonogenic assay. Each point represents the mean of three replicates from different experiments.
linear-quadratic model with the parameters ~ and f. The surviving fraction at a dose of 2 Gy ( S F 2 ) was calculated from c~- and/%values. The mean inactivation dose (D) was determined according to Fertil et al. [ 6].
to be very sensitive to irradiation (D 0.98 and 0.82 Gy, respectively). The D for OVC NOVA cells was 1.31 Gy. Among the four ovarian cancer cell lines, the OV B09 cell line was the least sensitive to radiation (D 1.94 Gy). The ~- and/~-values, SF 2 and D are summarized in Table II. Survival curves constructed from the data obtained by using the liquid culture assay did not differ significantly from those obtained by using the semi-solid agar assay.
Results The radiation survival curves of the four ovarian cancer cell lines, determined on the basis of surviving cell colonies in the semi-solid agar assays, are shown in Figs. 1-4. The cloning efficiency of the cell lines in agar varied between 1.4 and 5.2~o. The OV 166 and OV 1225 cell lines were found
Discussion We found two of the four ovarian cancer cell lines (OV 166 and OV 1225) to be highly sensitive to
Surviving f r a c t i o n
Surviving f r a c t i o n
0.1
0.1
\.
0.01
o.o1
0.001
"~-d
0.001 0
2
4
6
8
Dose (Gy)
Fig. 2. Radiation survival curve of OV 166 cells determined by clonogenic assay. Each point represents the mean of three replicates from different experiments.
,
0
2
4
6
-
-
-
-
8
Dose (Gy)
Fig. 4. Radiation survival curve of OV B09 cells determined by clonogenic assay. Each point represents the mean of three replicates from different experiments.
326 TABLE I1 Radiosensitivity of human ovarian cancer cell lines expressed by the parameters ct, fl, mean inactivation dose (9) and surviving fraction at 2 Gy (SF2).
OVC NOVA OV 166 OV 1225 OV B09
/~
D
(10) a
(100) a
(Gy)
(Gy- 1)
(Gy- 2)
7.24 (0.24)a 9.33 (0.28) 10.01 (0.85) 4.26 (0.19)
1.66 (0.38) 5.11 (0.30) 15.49 (0.90) 2.60 (0.57)
1.31 (0.06) 0.98 (0.03) 0.82 (0.05) 1.94 (0.10)
SF2
0.22 (0.01) 0.13 (0.02) 0.07 (0.02) 0.38 (0.02)
Standard deviation. radiation. The OVC N O V A and OV B09 cell lines were less radiosensitive (D 1.31 and 1.94Gy, respectively). Interestingly, the OV B09 cell line had a population doubling time that is about four times longer than that of the other cell lines. The present results are comparable to those reported by Rofstad et al. [ 15], who found the D O of ovarian cancer cells in vitro to range from 0.61 to 1.60 G y and the SF 2 value from 0.17 to 0.47. In a later study, Rofstad and Sutherland [14] reported that changes in the experimental conditions did not result in significant differences in radiosensitivity of the ovarian cancer cell lines. The use of in vitro radiation sensitivity data to predict the radiation response of human tumors has been a matter of dispute. Using the multitarget model, with Do and n-value as parameters, a great inter-assay variability and a lack of correlation with clinical tumor response to irradiation is frequently reported [6]. However, it has been demonstrated in a large number of h u m a n tumor cell lines that the in vitro radiosensitivity shows a good correlation with the clinical response to radiation, when in vitro d a t a are analyzed using the parameters SF2, ~ and D [2,6-8,11]. These parameters accurately describe the initial part of the survival curve, which appears to be the most relevant part of the curve and to be cell line specific [7,8]. The in vitro radiosensitivity data of ovarian cancer cells support the view that ovarian cancer is a radioresponsive tumor. However, the pattern
of metastatic spread of ovarian cancer throughout the whole abdominal cavity limits the use of external radiotherapy. Therefore, the intraperitoneal administration of the radiocolloid 32p has been used to reach all areas at risk [1,21,24]. In particular, patients with no, or microscopical disease at second-look laparotomy may benefit from such an approach [1,21,24]. This technique might improve even further when the radiation effect can be targeted more specifically to tumor cells, for example by using monoclonal antibodies [5,22,23].
Acknowledgement
We thank Mr. J. van de Berg, Department of Radiation Therapy, for technical assistance.
References
1 Buchsbaum, H.J., Keetel, W.C. and Latourette, H.W. The use of radioisotopes as adjunct therapy of localized ovarian cancer. Semin. Oncol. 2: 247-251, 1975. 2 Deacon, J., Peckham, M. J. and Steel, G.G. The radioresponsiveness of human tumours and the initial slope of the cell survival curve. Radiother. Oncol. 2: 317-323, 1984. 3 Dembo, A.J. Radiotherapeutic management of ovarian cancer. Semin. Oncol. 11: 238-250, 1984. 4 Dembo A.J. Abdominopelvic radiotherapy in ovarian
327
5
6
7
8
9
10
11
12
13
14
cancer. A 10-year experience. Cancer 55: 2285-2290, 1985. Epenetos, A.A., Hooker, G., Knausz, T, Snook, D., Bodmer, W. F. and Taylor-Papadimitriou, J. Antibodyguided irradiation of malignant ascites in ovarian cancer: a new therapeutic method possessing specificity against cancer cells. Obstet. Gynecol. 68: 71S-74S, 1986. Fertil, B., Dertinger, H., Courdi, A. and Malaise, E.P. Mean inactivation dose: a useful concept for intercomparison of human cell survival curves. Radiat. Res. 99: 73-84, 1984. Fertil, B. and Malaise, E.P. Inherent cellular radiosensitivity as a basic concept for human tumor radiotherapy. Int. J. Radiat. Oncol. Biol. Phys. 7: 621-629, 1981. Fertil, B. and Malaise, E.P. Intrinsic radiosensitivity of human cell lines is correlated with radioresponsiveness of human tumors: analysis of 101 published survival curves. Int. J. Radiat. Oncol. Biol. Phys. 11: 1699-1707, 1985. Hacker, N.F., Berek, J. S., Burnison, C.M., Heintz, A. P. M., Juillard, G. J. F. and Lagasse, L. D. Whole abdominal radiation as salvage therapy for epithelial ovarian cancer. Obstet. Gynecol. 65: 60-66, 1985. Hoskins, W. J., Lichter, A. S., Whittington, R., Artman, L. E., Bibro, M. C. and Park, R.C. Whole abdominal and pelvic irradiation in patients with minimal disease at second-look surgical reassessment for ovarian carcinoma. Gynecol. Oncol. 20: 271-280, 1985. Malaise, E. P., Fertil, B., Chavaudra, N. and Guichard, M. Distribution of radiation sensitivities for human tumor cells of specific histological types: comparison of in vitro to in vivo data. Int. J. Radiat. Oncol. Biol. Phys. 12: 617-624, 1986. Menczer, J., Modan, M., Brenner, J., Ben-Barach, G. and Brenner, H. Abdominopelvicirradiation for Stage II-IV ovarian carcinoma patients with limited or no residual disease at second-look laparotomy after completion of cisplatinum-based combination chemotherapy. Gynecol. Oncol. 24: 149-154, 1986. Peters, W.A., III, Blasko, J.C., Bagley, C.M., Jr., Rudolph, R. H., Smith, M. R. and Rivkin, S.E. Salvage therapy with whole-abdominal irradiation in patients with advanced carcinoma of the ovary previously treated by combination chemotherapy. Cancer 58: 880-882, 1986. Rofstad, E. K. and Sutherland, R.M. Radiation sensitivity of human ovarian carcinoma cell lines in vitro:
15
16
17
18
19
20
21
22
23
24
effects of growth factors and hormones, basement membrane, and intercellular contact. Int, J. Radiat. Oncol. Biol. Phys. 15: 921-929, 1988. Rofstad, E. K., Wahl, A. and Brustad, T. Radiation sensitivity in vitro of cells isolated from human tumor surgical specimens. Cancer Res. 47: 106-110, 1987. Schray, M.F., Martinez, A., Haves, A.E., Podratz, K.C., Ballon, S.C., Malkasian, G.D., Jr. and Sikic, B.I. Advanced epithelial ovarian cancer: salvage whole abdominal irradiation for patients with recurrent or persistent disease after combination chemotherapy. J. Clin. Oncol. 6: 1433-1439, 1988. Slotman, B. J. and Rao, B.R. Ovarian cancer (Review). Etiology, diagnosis, prognosis, surgery, radiotherapy, chemotherapy and endocrine therapy. Anticancer Res. 8: 417-434, 1988. Slotman, B. J. and Rao, B.R. Response to inhibition of androgen action of human ovarian cancer cells in vitro. Cancer Lett. 45: 213-220, 1989. Slotman, B.J., Poels, L.G. and Rao, B.R. A direct LHRH-agonist action on cancer cells is unlikely to be the cause of response to LHRH-agonist therapy. Anticancer Res. 9: 77-80, 1989. Smith, J. P., Rutledge, F. N. and Declos, L. Postoperative treatment of early cancer of the ovary: a random trial between postoperative irradiation and chemotherapy. Natl. Cancer Inst. Monogr. 42: 149-153, 1975. Spencer, T. R., Jr., Marks, R. D., Jr., Fenn, J. O., Jenrette, J.M., III and Lutz, M.H. Intraperitoneal P-32 after negative second-look laparotomy in ovarian carcinoma. Cancer 63: 2434-2437, 1989. Stewart, J. S.W., Hird, V., Snook, D., Sullivan, M., Myers, M. J. and Epenetos, A.A. Intraperitoneal ~3~Iand 9°Y-labelled monoclonal antibodies for ovarian cancer: pharmacokinetics and normal tissue dosimetry. Int. J. Cancer 3 (Suppl.): 71-76, 1988. Ward, B.G., Mather, S.J., Hawkins, R., Crowther, M.E., Shepherd, J. H., Granowska, M., Britton, K. E. and Slevin, M.L. Localisation of radioiodine conjugated to the monoclonal antibody HMFG2 in human ovarian carcinoma. Assessment of intraperitoneal and intravenous routes of administration. Cancer Res. 47: 4719-4727, 1987. Varia, M., Rosenman, J., Venkatraman, S. et al. Intraperitoneal chromic phosphate after second-look laparotomy for ovarian cancer. Cancer 61: 919-927, 1988.
323
RADION 00786
Ovarian cancer" radiation sensitivity in vitro B. J. Slotman l, A. B. M. F. K a r i m 2 a n d B. R. Rao Department of 1Endocrinology and :Radiation Therapy, Academisch Ziekenhuis Vrije Universiteit, Amsterdam, The Netherlands (Received 27 September 1989, revision received 7 February 1990, accepted 19 June 1990)
Key words." Ovarian cancer; Radiosensitivity; In vitro
Summary The radiosensitivity of four human ovarian cancer cell lines was investigated in vitro by a clonogenic assay and analyzed using the linear-quadratic model. Two cell lines were found to be highly radiosensitive (mean inactivation dose (D) 0.82-0.92 Gy; surviving fraction 2 Gy (SF2) ~<0.13). Two other cell lines were less sensitive to radiation (D 1.31-1.94 Gy; SF 2 0.22-0.38). Although the use of external radiotherapy in ovarian cancer has been limited due to the pattern of metastatic spread of this cancer, the present data support the view that ovarian carcinomas are radiosensitive tumors. Investigations on the effects of new approaches, such as delivering radiation more specifically to intraperitoneal ovarian cancer cells, are warranted.
Introduction The role of radiation therapy in the treatment of ovarian cancer has been the subject of considerable controversy during the last decades. It has been demonstrated that pelvic irradiation is ineffective in ovarian cancer, since relapses may occur throughout the whole peritoneal cavity [3,17 ]. Whole abdominal irradiation has been used as an adjuvant to surgery [3,4,20] and as salvage therapy for patients with recurrent or persistent disease Addressfor correspondence:B. Ramanath Rao, Ph.D., Department of Endocrinology, Academisch Ziekenhuis Vrije Universiteit, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands.
following chemotherapy [ 9,10,12,13,16 ]. Little is known about the intrinsic radiosensitivity of ovarian cancer cells. We have investigated the radiosensitivity of four human ovarian cancer cell lines by in vitro cell culture techniques.
Materials and methods Cell cultures
The three established ovarian cancer cell lines (OVC NOVA, passage 190-198; OV 166, passage 31-39 and OV 1225 passage 30-37) have been initiated from tumors or ascites fluid of patients with ovarian cancer of the common epithelial type
0167-8140/90/$03.50 © 1990 Elsevier Science Publishers B.V. (Biomedical Division)
324 TABLE I Population doubling time, DNA-index (2 n = 1) and S-phase fraction (SPF) of four human ovarian cancer cell lines.
OVCNOVA OV 166 OV 1225 OV B09
Doubling time (h)
DNA-index
SPF (%)
35 30 40 150
1.7 1.1 2.0 1.6
22 24 17 16
[18,19]. The OV B09 cell line (passage 5-7) was initiated from ascitic fluid of a patient with serous adenocarcinoma of the ovary, 4 months prior to the experiments. Immunohistochemical analysis of these cell lines showed reactivity with the ovarian cancer monoclonal antibodies OC 125 and OVTL-3. Microscopically, the cell lines display epithelial cell types. The population doubling times and Sphase-fractions (SPF), determined during exponential growth phase, as well as the DNAindices of the cell lines are given in Table I. The cell cultures were maintained at 37 °C in 5 ~ CO2 in air in R P M I 1640 medium (Gibco Ltd., U.K.), supplemented with fetal calf serum (10~o v/v; Gibco Ltd., U.K.), transferrin (Sigma Chem., U.S.A.) 5/~g/ml, insulin (Novo Industry BV, Holland) 5/~g/ml, and gentamycin (Gibco Ltd., U.K.), 50 #g/ml. Since identification of distinct colonies in monolayer culture was difficult due to confluency and spreading of cells, we optioned for a semisolid agar assay. Irradiation
Immediately before irradiation, cells were trypsinised, counted using a cell counter (Sysmex Microcell counter CC-110) and pipetted into replicate tubes at concentrations of 10, 50, 100, 500 and 1000 × 103 cells/ml. The cells were irradiated using fractions of 0.5-10 Gy using a 250 kV orthovolt unit (Philips) at a dose-rate of 0.7 Gy/min. During irradiation, the cells were kept at room temperature for less than 1 h. In
preliminary experiments we found that maintaining the cells under these conditions for 1 h did not result in a decreased colony formation, as compared to cells maintained at 37 °C. After irradiation, the cell suspensions were mixed 1 : 1 with a sterile 0.5~o solution of agar (Bacto-agar, Difco, U.S.A.) in phosphate buffer saline (PB S) at 37 ° C. The mixture was layered in tissue culture wells (Tissue Culture Cluster 6, Costar, U.K.) above an underlayer of semi-solid agar mixture (1:3) of the culture medium and 0.5~o agar in PBS. The agar mixture was cooled down to room temperature and then put in an incubator (37 °C, 5 ~ CO 2 in air). Since in preliminary experiments no difference in cloning efficiency and radiation response was observed with and without the inclusion of feeder cells, in subsequent experiments no feeder cells were included. Ten days after irradiation, the number of colonies (comprising more than 50 cells) arising in agar was determined by phase-contrast microscopy. For all four cell lines, a linear relationship between the number of cells plated and the number of colonies formed was found. The cloning efficiency of the irradiated cells was calculated and compared to that of the untreated control cells. The surviving fraction was calculated by dividing the mean cloning efficiency of the irradiated cells by the cloning efficiency of the untreated control cells. In addition, we have investigated the effect of irradiation on the cell proliferation of cultures grown in liquid medium monolayer cultures. Cells in monolayer culture were irradiated in the exponential growth phase. After irradiation, the flasks were put in an incubator (37 °C, 5~o CO2 in air). Nine days after irradiation, the cells were trypsinised and counted using a cell counter. The surviving fraction was calculated by dividing the number of cells after irradiation by the number of cells in the untreated control flasks. Survival curve analysis
Survival curves were generated from at least two experiments for each cell line, according to the
325 Surviving fraction
Surviving fraction
1
0.1
0.1
0.01
0,01
0.001
0.001 2
4
6
2
8
, 4
r 6
8
Dose (Gy)
Dose (Gy)
Fig. 1. Radiation survival curve of OVC NOVA cells determined by clonogenie assay. Each point represents the mean of three replicates from different experiments.
Fig. 3. Radiation survival curve of OV 1225 cells determined by clonogenic assay. Each point represents the mean of three replicates from different experiments.
linear-quadratic model with the parameters ~ and f. The surviving fraction at a dose of 2 Gy ( S F 2 ) was calculated from c~- and/%values. The mean inactivation dose (D) was determined according to Fertil et al. [ 6].
to be very sensitive to irradiation (D 0.98 and 0.82 Gy, respectively). The D for OVC NOVA cells was 1.31 Gy. Among the four ovarian cancer cell lines, the OV B09 cell line was the least sensitive to radiation (D 1.94 Gy). The ~- and/~-values, SF 2 and D are summarized in Table II. Survival curves constructed from the data obtained by using the liquid culture assay did not differ significantly from those obtained by using the semi-solid agar assay.
Results The radiation survival curves of the four ovarian cancer cell lines, determined on the basis of surviving cell colonies in the semi-solid agar assays, are shown in Figs. 1-4. The cloning efficiency of the cell lines in agar varied between 1.4 and 5.2~o. The OV 166 and OV 1225 cell lines were found
Discussion We found two of the four ovarian cancer cell lines (OV 166 and OV 1225) to be highly sensitive to
Surviving f r a c t i o n
Surviving f r a c t i o n
0.1
0.1
\.
0.01
o.o1
0.001
"~-d
0.001 0
2
4
6
8
Dose (Gy)
Fig. 2. Radiation survival curve of OV 166 cells determined by clonogenic assay. Each point represents the mean of three replicates from different experiments.
,
0
2
4
6
-
-
-
-
8
Dose (Gy)
Fig. 4. Radiation survival curve of OV B09 cells determined by clonogenic assay. Each point represents the mean of three replicates from different experiments.
326 TABLE I1 Radiosensitivity of human ovarian cancer cell lines expressed by the parameters ct, fl, mean inactivation dose (9) and surviving fraction at 2 Gy (SF2).
OVC NOVA OV 166 OV 1225 OV B09
/~
D
(10) a
(100) a
(Gy)
(Gy- 1)
(Gy- 2)
7.24 (0.24)a 9.33 (0.28) 10.01 (0.85) 4.26 (0.19)
1.66 (0.38) 5.11 (0.30) 15.49 (0.90) 2.60 (0.57)
1.31 (0.06) 0.98 (0.03) 0.82 (0.05) 1.94 (0.10)
SF2
0.22 (0.01) 0.13 (0.02) 0.07 (0.02) 0.38 (0.02)
Standard deviation. radiation. The OVC N O V A and OV B09 cell lines were less radiosensitive (D 1.31 and 1.94Gy, respectively). Interestingly, the OV B09 cell line had a population doubling time that is about four times longer than that of the other cell lines. The present results are comparable to those reported by Rofstad et al. [ 15], who found the D O of ovarian cancer cells in vitro to range from 0.61 to 1.60 G y and the SF 2 value from 0.17 to 0.47. In a later study, Rofstad and Sutherland [14] reported that changes in the experimental conditions did not result in significant differences in radiosensitivity of the ovarian cancer cell lines. The use of in vitro radiation sensitivity data to predict the radiation response of human tumors has been a matter of dispute. Using the multitarget model, with Do and n-value as parameters, a great inter-assay variability and a lack of correlation with clinical tumor response to irradiation is frequently reported [6]. However, it has been demonstrated in a large number of h u m a n tumor cell lines that the in vitro radiosensitivity shows a good correlation with the clinical response to radiation, when in vitro d a t a are analyzed using the parameters SF2, ~ and D [2,6-8,11]. These parameters accurately describe the initial part of the survival curve, which appears to be the most relevant part of the curve and to be cell line specific [7,8]. The in vitro radiosensitivity data of ovarian cancer cells support the view that ovarian cancer is a radioresponsive tumor. However, the pattern
of metastatic spread of ovarian cancer throughout the whole abdominal cavity limits the use of external radiotherapy. Therefore, the intraperitoneal administration of the radiocolloid 32p has been used to reach all areas at risk [1,21,24]. In particular, patients with no, or microscopical disease at second-look laparotomy may benefit from such an approach [1,21,24]. This technique might improve even further when the radiation effect can be targeted more specifically to tumor cells, for example by using monoclonal antibodies [5,22,23].
Acknowledgement
We thank Mr. J. van de Berg, Department of Radiation Therapy, for technical assistance.
References
1 Buchsbaum, H.J., Keetel, W.C. and Latourette, H.W. The use of radioisotopes as adjunct therapy of localized ovarian cancer. Semin. Oncol. 2: 247-251, 1975. 2 Deacon, J., Peckham, M. J. and Steel, G.G. The radioresponsiveness of human tumours and the initial slope of the cell survival curve. Radiother. Oncol. 2: 317-323, 1984. 3 Dembo, A.J. Radiotherapeutic management of ovarian cancer. Semin. Oncol. 11: 238-250, 1984. 4 Dembo A.J. Abdominopelvic radiotherapy in ovarian
327
5
6
7
8
9
10
11
12
13
14
cancer. A 10-year experience. Cancer 55: 2285-2290, 1985. Epenetos, A.A., Hooker, G., Knausz, T, Snook, D., Bodmer, W. F. and Taylor-Papadimitriou, J. Antibodyguided irradiation of malignant ascites in ovarian cancer: a new therapeutic method possessing specificity against cancer cells. Obstet. Gynecol. 68: 71S-74S, 1986. Fertil, B., Dertinger, H., Courdi, A. and Malaise, E.P. Mean inactivation dose: a useful concept for intercomparison of human cell survival curves. Radiat. Res. 99: 73-84, 1984. Fertil, B. and Malaise, E.P. Inherent cellular radiosensitivity as a basic concept for human tumor radiotherapy. Int. J. Radiat. Oncol. Biol. Phys. 7: 621-629, 1981. Fertil, B. and Malaise, E.P. Intrinsic radiosensitivity of human cell lines is correlated with radioresponsiveness of human tumors: analysis of 101 published survival curves. Int. J. Radiat. Oncol. Biol. Phys. 11: 1699-1707, 1985. Hacker, N.F., Berek, J. S., Burnison, C.M., Heintz, A. P. M., Juillard, G. J. F. and Lagasse, L. D. Whole abdominal radiation as salvage therapy for epithelial ovarian cancer. Obstet. Gynecol. 65: 60-66, 1985. Hoskins, W. J., Lichter, A. S., Whittington, R., Artman, L. E., Bibro, M. C. and Park, R.C. Whole abdominal and pelvic irradiation in patients with minimal disease at second-look surgical reassessment for ovarian carcinoma. Gynecol. Oncol. 20: 271-280, 1985. Malaise, E. P., Fertil, B., Chavaudra, N. and Guichard, M. Distribution of radiation sensitivities for human tumor cells of specific histological types: comparison of in vitro to in vivo data. Int. J. Radiat. Oncol. Biol. Phys. 12: 617-624, 1986. Menczer, J., Modan, M., Brenner, J., Ben-Barach, G. and Brenner, H. Abdominopelvicirradiation for Stage II-IV ovarian carcinoma patients with limited or no residual disease at second-look laparotomy after completion of cisplatinum-based combination chemotherapy. Gynecol. Oncol. 24: 149-154, 1986. Peters, W.A., III, Blasko, J.C., Bagley, C.M., Jr., Rudolph, R. H., Smith, M. R. and Rivkin, S.E. Salvage therapy with whole-abdominal irradiation in patients with advanced carcinoma of the ovary previously treated by combination chemotherapy. Cancer 58: 880-882, 1986. Rofstad, E. K. and Sutherland, R.M. Radiation sensitivity of human ovarian carcinoma cell lines in vitro:
15
16
17
18
19
20
21
22
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