518 Retrospective analysis of overall survival and pattern of relapse utilising sequential chemoradiotherapy in high-risk endometrial cancer

Introduction/Background* Management of endometrial cancer (EC) consists of surgery, followed by tailored adjuvant therapy in intermediate to high-risk disease. PORTEC3 reported 5-year overall survival (OS) of 81% and 25% relapse rate (pelvic failure 6% and distant failure 24%) in women who received concurrent chemoradiotherapy followed by 4 cycles of chemotherapy, with most marked benefit demonstrated in stage III and/or high grade serous (HGS) EC. In the West of Scotland Cancer Network (WoSCAN), standard post-operative protocol for high-risk disease is 4–6 cycles of carboplatin/paclitaxel prior to external beam radiotherapy (EBRT), 4500cGy/25 fractions. We compared our practice to PORTEC3 to investigate if alternative sequencing affects OS and/or pattern of relapse. Methodology Data were collected retrospectively from electronic clinical records in WoSCAN patients who commenced adjuvant chemotherapy between January 2012 and December 2016. Statistical analysis was performed using R®. OS was estimated using Kaplan-Meier method. Result(s)* 108 patients were identified, 57 had chemotherapy +/- vaginal brachytherapy and 51 had chemotherapy + EBRT. In the EBRT cohort, median age was 62 years (range 47-78), and FIGO stage was as follows: IB (13%); II (18%); III (59%); IVB (10%). LVSI was positive in 69% and nodal staging performed in 39%. Pathology consisted of: EEC (61%), HGS (22%), carcinosarcoma (10%), or other (7%). Residual disease and/or positive margins were present in over 10%. Median number of chemotherapy cycles was 4 (range 3-6), and 37% had 5 or 6 cycles. 95% completed EBRT. OS at 3-years was 72% (95% Confidence Interval 61-86). Relapse rate was 39% (pelvic failure 17% and distant failure 33%). Conclusion* Pelvic and distant failure rates were higher and OS was less favourable in our series, but over 30% of patients would have been excluded from the PORTEC3 trial based on pathology, stage, and residual disease. Chemotherapy prior to EBRT does not appear to result in better outcomes, but this cohort consisted of women with very high-risk EC.