Risk Without Reward: Differing Patterns of Chemotherapy Use Do Not Improve Outcomes in Stage II Early-Onset Colon Cancer

PURPOSERising rates of early-onset colon cancer (EOCC) present challenges in deciding how to optimally treat patients. Although standard of care for stage II CC is surgical resection, adding chemotherapy for high-risk disease, evidence suggests treatment selection may differ by age. We investigated whether adjuvant chemotherapy (AC) administration rates differ between patients with early- and later-onset stage II CC.METHODSData originated from the nationwide Flatiron Health electronic health record (EHR)-derived deidentified database spanning January 1, 2003, to August 1, 2021. Adults with stage II CC were grouped as age 18-49 years (EOCC) and those age 50 years or older (later-onset colon cancer [LOCC]). Demographics, Eastern Cooperative Oncology Group score, tumor stage and site, and chemotherapy were included. Primary outcomes included rates of AC administration by age and ethnicity; secondary outcomes included overall survival (OS) and time to metastatic disease (TTMD). Univariate and multivariable logistic regression models evaluated relationships between chemotherapy administration, age, and ethnicity, adjusting for significant covariates.RESULTSOne thousand sixty-five patients were included. Median age of patients with EOCC was 45.0 years versus 69.0 years for patients with LOCC. Adjusted multivariate analysis showed patients with EOCC received AC significantly more often than patients with LOCC. Non-Hispanic patients received AC at significantly lower rates than Hispanic patients in both cohorts. Subanalysis of stage IIA patients showed that patients with EOCC were more likely to receive AC than patients with LOCC. No significant differences in OS or TTMD were observed by age regardless of AC administration in stage II overall; however, patients with stage IIA EOCC receiving AC had significantly longer TTMD than those not receiving AC.CONCLUSIONAC was given preferentially in stage II EOCC, even in stage IIA, despite deviation from guidelines. This may expose low-risk patients to unnecessary toxicities and suggests bias toward treating younger patients more aggressively, despite unclear evidence for better outcomes.