Survival among colorectal cancer patients with a history of previous cancer.

Abstract

e16146 Background: A growing number of patients with colorectal cancer (CRC) have survived a previous cancer. Although little is known about their prognosis, this population is frequently excluded from clinical trials. We examined the impact of previous cancer on overall and cancer-specific survival in a population-based cohort of patients diagnosed with incident CRC. Methods: We identified patients aged ≥66 years and diagnosed with CRC between 2005-2015 in linked SEER-Medicare data. For patients with and without previous cancer, we estimated overall survival using Cox regression and cause-specific survival using competing risk regression, separately by CRC stage, while adjusting for numerous covariates and competing risk of death from previous cancer, other causes, or the incident CRC. Results: Of 112,769 CRC patients diagnosed with incident CRC, 15,935 (14.1%) had a previous cancer – most commonly prostate (32.9%) or breast (19.4%) cancer, with many 7505 (47.1%) diagnosed ≤5 years of CRC. For all CRC stages except IV in which there was no significant difference in survival, patients with previous cancer had modestly worse overall survival (hazard ratios from fully adjusted models range from 1.11-1.28 across stages; see Table). This survival disadvantage was driven by deaths due to previous cancer and other causes. Notably, most patients with previous cancer had improved CRC-specific survival. Conclusions: CRC patients who have survived a previous cancer have generally worse overall survival but superior CRC-specific survival. This evidence should be considered concurrently with concerns about trial generalizability, low accrual, and heterogeneity of participants when determining exclusion criteria. [Table: see text]