Impact of adjuvant therapy in patients with a microscopically positive margin after resection for gastric and esophageal cancers.

Background: A microscopically positive (R1) resection margin following resection for gastric and esophageal cancers 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 with gastric and esophageal adenocarcinoma treated at the Princess Margaret Cancer Centre (PMCC) from 2006-2016. Electronic medical records of all patients 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 69 gastric and esophageal adenocarcinoma patients with a R1 resection. Neoadjuvant chemoradiation was used in 13% of patients, neoadjuvant chemotherapy in 12%, surgery alone in 75%. Margins involved included proximal in 30%, distal in 14%, radial in 52% and multiple margins in 3% of patients. Pathological staging showed 3% with stage I disease, 20% stage II and 74% stage III. Adjuvant therapy was given in 52% of R1 pts (28% CRT, 20% chemotherapy alone, 3% radiation alone, 1% reoperation). Median RFS was 14.1 months [95% confidence interval (CI), 11.1-17.2]. The site of first recurrence was 72% distant, 12% mixed, 16% locoregional alone. Median OS was 34.5 months (95% CI, 23.3-57.9) for all patients. There was no significant difference in RFS (adjusted P=0.26) or OS (adjusted P=0.83) comparing modality of adjuvant therapy.

Conclusions: Most patients with positive margins after resection for gastric and esophageal cancer had advanced pathologic stage and prognosis was poor. Our study did not find improved RFS or OS with adjuvant treatment and only one patient had reresection. The main failure pattern was distant recurrence, suggesting that patients being considered for adjuvant radiotherapy (RT) should be carefully selected. Further studies are required to determine factors to select patients with good prognosis despite a positive margin, or those who may benefit from adjuvant treatment.