Characteristics and Outcomes of Patients With Malignancies Prior to Colorectal Cancer: A Propensity Score Matched Analysis.

Colorectal cancer(CRC) is the third most commonly diagnosed malignancy with a rising global incidence. CRC shares many risk factors with other malignancies and may occur as a part of hereditary cancer syndromes. This retrospective cohort study aims to evaluate outcomes in patients with CRC and a history of prior malignancy to identify potential implications for personalized management. The National Cancer Database was queried from 2004 to 2022 for patients diagnosed with CRC, who were stratified into two cohorts: those with and without malignancies prior to CRC diagnosis. Propensity score matching was performed to balance sociodemographic characteristics, and logistic regression was used to estimate odds ratios(ORs) for tumor and treatment characteristics. Subsequently, a Cox proportional hazards model was fit to assess the association of having prior malignancies and mortality. A total of 576,076 patients were included, with 288,038 in each cohort. Patients with prior malignancies had significantly lower odds of KRAS mutation(OR = 0.86, 95% CI:0.83-0.89, p < 0.001), abnormal CEA levels(OR = 0.95, 95% CI:0.94-0.96, p < 0.001), perineural invasion(OR = 0.86, 95% CI:0.84-0.88, p < 0.001), early-onset CRC(OR = 0.73, 95% CI:0.71-0.74, p < 0.001), advanced-stage CRC(OR = 0.77, 95% CI:0.76-0.77, p < 0.001), and tumor deposits(OR = 0.82, 95% CI:0.80-0.84, p < 0.001). These patients also had higher odds of receiving treatment(OR = 1.05, 95% CI:1.02-1.08, p < 0.001). However, they had higher odds of microsatellite instability(OR = 1.20, 95% CI:1.17-1.23, p < 0.001), treatment delays(OR = 1.42, 95% CI:1.40-1.43, p < 0.001), and postoperative readmissions(OR = 1.14, 95% CI:1.11-1.17, p < 0.001). Patients with a history of prior malignancies were associated with higher overall mortality(aHR = 1.19, 95% CI:1.10-1.27, p < 0.001) as well as stage-specific mortality, except for stage 1 CRC. These findings indicate that patients with prior malignancies may require greater preoperative optimization, closer post-discharge monitoring, and proactive efforts to avoid treatment delays.