Total neoadjuvant oxaliplatin-based therapy (TNT) before (induction) and after (consolidation) chemoradiation for advanced rectal cancer: MRI correlation on complete response and outcome.

Abstract

165 Background: Preoperative chemoradiation with fluoropyrimidine, followed by total mesorectal excision (TME) and adjuvant chemotherapy is the standard care for locally advanced rectal cancer (LARC). Studies have shown the potential benefit of oxaliplatin based TNT approach. The benefits of using of both induction and consolidation chemotherapy with chemoradiation prior of TME is not well studied. We investigate whether the use of oxaliplatin based before (induction) and after (consolidation) neoadjuvant chemoradiation will increase the pCR and clinical Complete response (cCR), improve survival and MRI correlation. Methods: Patients treated with curative intent surgery for LARC who received oxaliplatin based induction and consolidation chemotherapy with neoadjuvant capecitabine chemoradiation were identified. Demographics and clinicopathologic data were analyzed. Multiparametric MRI was used for initial staging and restaging before surgery. The primary endpoint will be the complete response (pathological and clinical), recurrent-free survival (RFS), and overall survival (OS). Results: A total of 21 patients have been identified, all patient has T3/T4 and positive nodes N1/N2 on initial MRI staging, 2 (10%) patients had Stage IV disease with abdominal para-aortic nodes. Median age was 63 (range: 26-76); 14 (67%) male. As for the induction regimen, 9 (43%) had CAPOX/FOLFOX, 7 (33%) had short-course capecitabine, 5 (24%) had FOLFIRINOX. All patient received neoadjuvant chemoradiation with capecitabine. As for consolidation, 19 (90%) had CAPOX/FOLFOX, 1 (5%) had capecitabine and 1 (5%) had FOLFIRINOX. Median time for induction and consolidation chemotherapy was 8.5 weeks (range: 1-24) and 8 weeks (range: 2-16) respectively. Median time from starting induction chemotherapy to surgery was 6.8 months (range: 3.2-11). Eight (38%) patients had cCR and pCR. Post-treatment restaging MRI prior of resection has 100% concordant rate with pCR. All (100%) pateints had tumor downstaged after treated with TNT and chemoradiation. The sensitivity of MRI in detecting the residual lymph node post TNT/neoadjuvant chemoradiation was 55% (95% CI: 26-81%), and the negative predictive value was 75% (51-90%); the specificity was 100% (76-100%) and the positive predictive value was 100% (57-100%). There is no death and one patient had recurrence after recurrence free for 2 years. Median RFS and OS are not meet. Median follow up time is 25.7 months (range: 9.1-76.8). Conclusions: Neoadjuvant oxaliplatin based therapy before and after chemoradiation for rectal cancer potentially improves CR rate, and accurately predicted by post-treatment MRI. The use of MRI can potentially help to select candidates who desire organ preservation.