Rectosigmoid Cancer — Rectal Cancer or Sigmoid Cancer?

Abstract

<h3>Purpose/Objective(s)</h3> Locally advanced rectosigmoid adenocarcinomas are treated with either neoadjuvant (NA) chemoradiation or upfront surgery (sx). We determined outcomes with both treatment approaches and whether outcomes vary by anatomic landmarks. <h3>Materials/Methods</h3> We identified 161 pts with non-metastatic T3-T4 and/or N+ rectosigmoid cancers who underwent sx. with NA (radiation with or without chemotherapy) or adjuvant (adj) therapy from 2006 to 2018 at our institution. We included pts with available imaging and with primary tumor located 9-20 cm from the anal verge (AV) on staging CT, MRI, or colonoscopy. We reviewed the relationship of the primary tumor to the peritoneal reflection (PR) and sacral promontory (SP). Comparisons between the NA and adj. groups were performed using Fisher's exact test. Cumulative incidence of locoregional failure (LRF), distant failure (DF), and overall survival (OS) were compared using Kaplan-Meier. <h3>Results</h3> Of the study cohort, 97 pts had NA therapy and 64 pts had upfront sx. Median follow-up was 45.1 months. Pts who had NA therapy were younger, had tumors that were lower and more likely below the PR and with threatened circumferential resection margins (CRM), fewer cycles of adj chemotherapy, and higher cT stage (Table 1). The 3-year OS was 97.5% in the NA group versus 93.7% for upfront sx 2-year cumulative incidence of LRF was 5.2% (NA) vs 5.6% (upfront sx), <i>P</i> = 0.91. 2-year cumulative incidence of DF was 9.2% (NA) vs 10.4% (upfront sx), <i>P</i> = 0.54. Of the 10 pts total with LRF, 8 and 6 occurred in pts with tumors straddling/above the PR and > 10 cm from AV on imaging, respectively. None of the 3 pts with tumors < 10 cm from AV (MRI) treated with NA had LRF, while 16.7% (1/6) of these pts who received upfront sx had LRF. None of the 15 pts with tumors below the PR treated with NA had LRF, while 25% (1/4) of these pts who received upfront sx had LRF. Outcomes did not vary by relationship to the SP. <h3>Conclusion</h3> Pts with locally advanced rectosigmoid cancer treated with NA therapy had tumors closer to the AV and more advanced primaries. Despite these negative prognostic factors, they had cancer control outcomes similar to pts with higher, lower stage tumors treated with upfront sx. Pts with tumors below the PR or < 10 cm from AV may derive more benefit from NA therapy.