329P Duration of adjuvant therapy in stage III colon cancer: A real world multi-institutional US-based experience

Abstract

Since the publication of IDEA, the duration of adjuvant chemotherapy (CTX) in stage III colon cancer (CC) has shifted to a risk-stratified approach as 3 months (mo) of CAPOX vs 6 mo was found to be non-inferior in patients (pts) with low risk (LR) (T1-T3/N0-N1). High risk (HiR) (T4 or N2) disease failed to show non-inferiority, however 3-year DFS differences were less than 2% and only .1% when pts received CAPOX. However in the US cohort, pts did not receive CAPOX, possibly due to capecitabine intolerance. Herein, we performed a real-world evaluation of CTX in US pts with stage III CC. A retrospective review of stage III CC pts treated from 2016-2022 from 5 US academic medical institutions was performed. Pts were stratified into 3mo vs 6mo of CTX, HiR vs LR, and CAPOX vs FOLFOX. 3-year DFS and adverse events were recorded. A total of 443 pts were included. In the overall population, no difference in 3-year DFS was observed in 3 vs 6 mo of CTX (69.3 vs 71.0%, hazard ratio [HR] = 1.26, 95% CI (0.74, 2.17), adjusted p [aP] = 0.40), numerically less than was observed in IDEA. HiR pts were observed to have detriment in 3-year DFS with 3mo vs. 6mo CTX (34.0% vs 62.9%, HR = 1.51, 95% CI (0.77, 2.99), aP=0.23). Grade 3 adverse events (AE) of nausea, diarrhea, and hand/foot syndrome from capecitabine were higher than reported in IDEA.Table: 329PDFS by treatment, duration and riskCTXN (Events)36 Months DFS6 mo FOLFOX255 (76)71.8%6 mo CAPOX54 (17)67.5%3 mo FOLFOX37 (9)68.8%3 mo CAPOX97 (16)69.4%HiR vs LR6 mo LR126 (23)82.3%6 mo HiR183 (70)62.9%3 mo LR102 (13)81.2%3 mo HiR32 (12)34.0% Open table in a new tab In this real-world experience we observed no DFS benefit in pts treated with 3 vs 6mo CTX. In HiR pts treated with 3mo CTX, we observed a lower 3-year DFS rate compared to 6mo of CTX. The findings were not statistically significant due to low number of events in this cohort and was significantly lower than reported in IDEA. AEs were more prevalent in US pts compared to non-US pts in IDEA, likely due to capecitabine intolerance. Our study is the first to assess 3mo vs 6mo capecitabine based adjuvant CTX in a risk stratified US population and suggests discrepancies in DFS and AEs compared to IDEA in US pts who received CAPOX.