Concomitant low dose-rate irradiation and cisplatin treatment in ovarian carcinoma cell lines sensitive and resistant to cisplatin treatment.

Human ovarian carcinoma parental and cisplatin-resistant cells were evaluated for their radiation sensitivity to high and low dose-rate irradiation and for the effectiveness of cisplatin in radiosensitization. The cisplatin resistant variant A2780cp showed increased radiation resistance for both low dose-rate (LDRI) and high dose-rate irradiation. For cisplatin treatment for 1 h before and after HDRI there was radiosensitization in only the cisplatin-resistant variant. Concomitant cisplatin treatment during LDRI resulted in radiosensitization in both cell lines with dose-modifying factors ranging from 1.6 to 5.8. In this case greater radiosensitization was achieved in the parental cell line. In both cell lines the dose-modifying factors were larger when the cisplatin was refreshed every 6 h instead of 12 h during LDRI. These data show that cisplatin may be a very effective radiosensitizer when given during LDRI which is used in brachytherapy.