Impact of adjuvant therapy in patients with a microscopically positive margin after resection for gastroesophageal cancer.

Abstract

164 Background: A microscopically positive (R1) resection margin following resection for gastroesophageal (GE) cancer has been documented to be a poor prognostic factor. The optimal strategy and impact of different modalities of adjuvant treatment for an R1 resection margin remain unclear. Methods: A retrospective analysis was performed for patients (pts) with GE cancer treated at the Princess Margaret Cancer Centre from 2006-2016. Electronic medical records of all pts with an R1 resection margin were reviewed. Kaplan-Meier and Cox proportional hazards methods were used to analyze recurrence free survival (RFS) and overall survival (OS) with stage and neoadjuvant treatment as covariates in the multivariate analysis. Results: We identified 78 GE cancer pts with an R1 resection. 11% had neoadjuvant chemotherapy, 14% chemoradiation (CRT), 75% surgery alone. 28% had involvement of the proximal margin, 13% distal, 56% radial, 3% had multiple positive margins. By the American Joint Committee on Cancer 7th edition classification, 88% had a pT3-4 tumour, 66% pN2-3 nodal involvement, 64% grade 3, 68% with lymphovascular invasion. 3% were pathological stage I, 21% stage II and 74% stage III. Adjuvant therapy was given in 46% of R1 pts (24% CRT, 18% chemotherapy alone, 3% radiation alone, 1% reoperation). Median RFS for all pts was 12.6 months (95% CI 10.3-17.2). Site of first recurrence was 71% distant, 16% locoregional, 13% mixed. Median OS was 29.3 months (95% CI 22.9-50) for all pts. The 5 year survival rate was 23% (95% CI 12%-43%). There was no significant difference in RFS (log-rank test p= 0.63, adjusted p= 0.14) or OS (log-rank test p= 0.68, adjusted p= 0.65) regardless of adjuvant therapy. Conclusions: Most pts with positive margins after resection for GE cancer had advanced pathologic stage and prognosis was poor. Our study did not find improved RFS or OS with adjuvant treatment and only one pt had reresection. The main failure pattern was distant recurrence, suggesting that pts being considered for adjuvant RT should be carefully selected. Further studies are required to determine factors to select pts with good prognosis despite a positive margin, or those who may benefit from adjuvant treatment.