Management of the positive pathologic circumferential resection margin in rectal cancer: A national cancer database (NCDB) study

Abstract

BackgroundThe circumferential resection margin (CRM) is a primary predictor of local recurrence and survival in rectal cancer, and an important consideration in guiding treatment. CRM is usually predicted preoperatively, so optimal management of an unexpected pathologic positive CRM involvement is debatable. We aimed to investigate the postoperative management of T3N0 rectal cancers with a positive pathologic CRM, and the impact of each strategy on survival. MethodsThe NCDB was reviewed for pathological T3N0 rectal cancer cases from 2010 to 2015, that received neoadjuvant chemotherapy, had surgical resection with pathological clear margins, but a positive pathologic CRM(disease≤2 mm from radial margin). The main outcomes were the incidence, treatment modalities used, and impact of each modality on survival. Univariate analysis evaluated the demographic and provider characteristics across treatment groups. Kaplan-Meier and Cox regression analysis assessed survival and factors associated with overall survival (OS). ResultsOf 1607 cases with a positive CRM, 65% (1045) received no adjuvant treatment and 35% (n = 562) received adjuvant chemotherapy (AC). After matching, the 1-, 3-, and 5-year OS rates were 98.5%, 88.6% and 76.6% for AC and 96.9%, 84.6% and 68.4% for with no treatment (p = .027). Factors independently associated with improved OS were treatment at an academic/research facility (p = .009), minimally invasive approach (p = .005), well and moderately differentiated tumor (p < .001), absence of perineural invasion (p = .015) and AC administration (p = .047). ConclusionIn T3N0 rectal cancers resected with local clear margins but a positive pathologic CRM, AC improved OS. However, only a third received this option. Further study is needed to investigate the disparities in AC use in these patients with unexpected pathologic results.