Radiologic and pathologic prognostic factors after neoadyuvant chemotherapy for T3 rectal cancer (RC): 3-year update GEMCAD 0801-trial.

Abstract

643 Background: Prognostic factors in RC treated only with neoadjuvant chemotherapy, have not been explored. We analized the prognostic value of clinical-radiological and pathological factors for disease-free, (DFS) and cumulative incidence of distant metastases (DM), for patients treated with preoperative capecitabine, oxaliplatin and bevacizumab (CAPOX-B) within our multicentre phase II GEMCAD 0801 trial. Methods: 46 patients were enrolled to evaluate safety and efficacy of neoadjuvant CAPOX-B followed by surgery. Results have been recently published (Oncologist 2014;19:1-2). Eligibility included baseline magnetic resonance (MR) showing a T3 tumour with mesorectal fascia potentially clear. Clinical, pathologic (ypN+, T or N downstaging, tumor regression grade [TRG], pathologic complete response [pCR]) and radiologic factors both at baseline (mr extramural venous invasion [EMVI]) and post neoadjuvant chemotherapy (ymr TRG, ymr lengh change [RECIST]), were analyzed. Univariate and multivariate analysis was performed. Results: With a median follow up of 36 months, fourteen patients experienced relapse (2 local, 11 distant, 1both). 3-year DFS was 69%. It was 95%/49% for T downstaging/no T downstaging (p=0.0009) and 95%/43% for mrEMVI positive/negative (p=0.0001), respectively. ymrTRG (Mandard) ranging from no regression, TRG 5, to complete response, TRG 1, p=0.0108 and ypN0/ypN+ (p=.02) were also significantly related to DFS in univariate analysis. The same factors and N-downstaging were also significant for cumulative incidence of DM. On Cox multivariate analysis, T downstaging and mrEMVI were the only independent prognostic factors for DM ( p=0.0363 and 0.0111 respectively) and DFS (p=0.0315 and 0.0277 respectively). Conclusions: T3 rectal cancer with MR detected EMVI positive and those without downstaging after neoadjuvant chemotherapy are associated with unfavourable prognosis. This suggests that future strategies for treatment intensification and surveillance could be based on EMVI and T staging. Clinical trial information: NCT00909987.