Adjuvant radiation for patients (pts) with high-grade serous ovarian cancer (HGSC) and T-cell infiltration.

5543 Background: CD8 positive intra-epithelial tumor infiltrating T cells (TIL) are associated with improved outcomes in ovarian cancer, particularly in HGSC. Radiotherapy (XRT) has immunologic effects including tumour necrosis, activation of antigen presenting cells and T cell recruitment. Adjuvant XRT in ovarian cancer was historically used at the BC Cancer Agency (BCCA). We hypothesized that adjuvant XRT for HGSC may have a beneficial impact on outcomes within the TIL+ subgroup. Methods: Stage I and II and optimally debulked (no visible residual disease) stage III HGSC pts treated at the BCCA from 1984to 2004 were included in this analysis. All cases underwent pathologic review to confirm histology and to score for TIL, either present (≥1 CD8 cell / 6mm core) or absent via immunohistochemistry. Treatment was platinum based chemotherapy (3-6 cycles) and abdominal-pelvic radiotherapy (45 Gy and 32 fractions to pelvis and whole abdomen). Kaplan-Meier and Cox proportional hazards methods were used to corre...