Treatment-interval associated effect of irradiation on locoregionally-relapsed ovarian cancer.

Recurrent ovarian cancer following chemotherapy is usually incurable, particularly when the tumor acquires a drug resistance. The present study aimed to define the effect of irradiation on locoregional recurrences and the impact of the factors on the efficacy. The study retrospectively reviewed the clinical records of 61 patients with epithelial ovarian cancer who received irradiation following repeated chemotherapy between 1997 and 2006. A positive-irradiation response was designated as complete response, partial response, minor response or no change (NC). Due to the possible synergistic effect of chemotherapy and irradiation, and the cross-resistance to chemotherapeutic drugs and radiation, the focus was on the treatment break between chemotherapy and radiation, and patients were classified into 3 categories: Category I, ≤1 month; II, 1-6 months; and III, >6 months. The effect of irradiation was analyzed in association with histology, treatment break, recurrent site, irradiation dose and chemosensitivity. The post-irradiation survival time was analyzed by the irradiation response and treatment category. The median biological-effective dose was 60.0 Gy (range, 15.6-72.0 Gy). The sites irradiated included nodal recurrence (36), abdominal (six) and pelvic cavity (five cases). Histologically, serous adenocarcinoma was the most common type of the disease (23 cases) compared to mucinous (four), endometrioid (three), and clear-cell types (six cases). The median survival times were 4.5 months in the radiation responders (13 cases) and 15.3 months in the non-responders (37) (P=0.004). The positive-irradiation response was significantly associated with the treatment break (P=0.026) and chemosensitivity (P=0.007). In conclusion, irradiation for recurrent ovarian cancer produced an improved survival benefit when applied to chemoresponsive, locoregional-recurrent tumors immediately following chemotherapy.