Propensity-Score Matched Analysis of Survival Outcomes of Adjuvant Therapy in Stage II-III Signet-Ring Cell Carcinoma of the Colon

This retrospective analysis assessed survival benefits of adjuvant therapy after curative resection of stage II-III colonic signet ring cell carcinoma (SRCC) using National Cancer Database (2010-2019) data. Patients who received/did not receive adjuvant therapy were matched using nearest neighbor propensity-score matching. Adjuvant therapy showed improved overall survival in stage III, right-sided, and transverse colonic SRCC. Survival benefit of adjuvant therapy in stage II and left-sided colon SRCC was limited. Background: Colonic signet ring cell carcinoma (SRCC) is a mucinous adenocarcinoma subtype often associated with poor prognosis. This study assessed the survival benefits of adjuvant therapy after curative resection of stage II-III colonic SRCC. Methods: This was a retrospective analysis of outcomes of adjuvant therapy in colonic SRCC using National Cancer Database (2010-2019) data. Patients who received adjuvant therapy were matched to those who did not use the nearest neighbor propensity-score matching. The primary outcome was 5-year overall survival (OS). Results: The unmatched cohort included 3530 patients. Patients who received adjuvant therapy were significantly younger, more often male, and more often had Charlson scores 0-1, left-sided cancers, stage III disease, lymphovascular invasion, and perineural invasion. The matched cohort included 958 patients (53.6% female); 479 received adjuvant therapy and 479 did not. Adjuvant therapy was associated with longer mean OS (39.9 vs. 29.2 months; P < .001)<bold>.</bold> Survival benefit of adjuvant therapy was evident in stage III disease (37.5 vs. 24.7 months; P < .001), right-sided colon cancer (40.2 vs. 27.7 months; P < .001), and transverse colon cancer (40.6 vs. 31.1 months; P = .002), but not stage II disease (52.1 vs. 53.1 months; P = .694) or left-sided colon cancer (35.8 vs. 32.6 months; P = .417). Independent predictors of improved OS were adjuvant therapy (HR: 0.539; P < .001), laparoscopic surgery (HR: 0.829; P = .001), robotic-assisted surgery (HR: 0.63; P = .007), and number of harvested lymph nodes (HR: 0.976; P < .001). Conclusions: Adjuvant therapy was associated with improved OS in stage III, right-sided, and transverse colon SRCC. The survival benefit of adjuvant therapy in stage II and left-sided colon SRCC was limited.