EP324 MRI-based tumor volume evaluation at the time of brachytherapy as a predictor of survival in cervical cancer patients treated with definitive chemoradiation

Introduction/Background To evaluate the potential impact on survival of residual tumor volume after chemoradiation and prior to brachytherapy initiation determined by magnetic resonance imaging in patients treated for locally advanced cervical cancer. Methodology MRI examinations were prospectively performed in patients with advanced cervical cancer (Stages IB2-IVA) after chemoradiation completion and prior to brachytherapy initiation. Region of interest-based 3D volumetry was derived on the treatment planning system by tracing the entire residual tumor region in each T2-weighted MRI slice. All patients received external beam radiation (EBRT) with concomitant weekly Cisplatin followed by high-dose rate endocavitary brachytherapy using volume-based planning. Cumulative EBRT and BT doses were calculated as the total equivalent dose in 2 Gy fractions (EQD2). Potential prognostic factors were selected based on non-parametric tests and then analyzed for survival with a Cox regression model. Results Median post-therapy follow-up was 27.4 months (range, 3–57.8). Thirty-seven patients were included. According to the FIGO classification, 8% were stage IB, 75% stage II, 11% stage III, and 6% stage IV. Overall survival was 86.5%. Of the patients evaluated, 29.7% had complete radiological remission and 18.9% were considered having local failure or distant disease. At bivariate analysis, residual volume >2 mL, D90 CTV-HR 2 mL, respectively (p=0.005). Conclusion Our data suggest that residual tumor volume >2 mL at the time of brachytherapy is a predictor of poor survival. Disclosure Nothing to disclose.