Lateral Pelvic Nodal Management and Patterns of Failure in Patients Receiving Short-Course Radiation for Locally Advanced Rectal Cancer.

Abstract

Management of lateral pelvic lymph nodes in locally advanced rectal cancer is controversial, with limited data indicating the optimal approach. Additionally, no data exists regarding treatment of lateral nodes in the setting of short course radiation and nonoperative intent. We evaluate a novel approach incorporating simultaneous integrated boost to suspicious lateral nodes. This was a retrospective study. This study was conducted at a large, tertiary referral center. Patients treated with radiation and consolidation chemotherapy were included. All primary tumors were biopsy confirmed and disease-staged with pelvic magnetic resonance imaging. Primary tumors were biopsy proven and staged with pelvic magnetic resonance imaging. A subset of lateral pelvic lymph nodes patients received simultaneous integrated boost to 35 Gy in 5 fractions. Then, chemotherapy was administered with the majority receiving mFOLFOX (modified folinic acid, fluorouracil, and oxaliplatin). Clinical partial response required total mesorectal excision. Patterns of failure and survival analyses by subgroup were assessed. Outcomes based on receipt of radiation were compared across node status. Between January 2017 - January 2022, 155 patients were treated with short course and chemotherapy with 121 included in final analysis. Forty-nine percent underwent nonoperative management. Median follow-up was 36 months and median age was 58 years. Thirty-eight patients (26%) had positive lateral pelvic lymph nodes. Comparing lateral node status, progression-free survival was significantly worse for patients with positive disease (p < 0.001) with a trend for worse overall survival. Receipt of nodal boost in patients with lateral nodes resulted in meaningful locoregional control. Nodal boost did not contribute to additional acute or late GI toxicity. Limitations included retrospective nature and lack of lateral nodes pathology; however, thorough radiographic review was performed. Lateral node positive rectal cancer is correlated with worse oncologic outcomes and higher locoregional failure. Boost to clinically positive lateral nodes is a safe approach in the setting of short course and in those receiving nonoperative intent.