Survival of patients newly diagnosed with colorectal cancer and with a history of previous cancer

Abstract Patients with previous cancer are often excluded from clinical trials despite limited evidence about their prognosis. We examined the effect of previous cancer on overall and colorectal cancer (CRC)‐specific survival of patients newly diagnosed with CRC. This population‐based cohort study from the U.S.A. included patients aged ≥66 years and diagnosed with CRC between 2005 and 2015 in linked Surveillance, Epidemiology, and End Results‐Medicare data. We estimated the stage‐specific effects of a previous cancer on overall survival using Cox regression and on CRC‐specific survival using competing risk regression. We also examined the effect of previous cancer type, timing, and stage on overall survival. Of 112,769 patients, 14.1% were previously diagnosed with another cancer––commonly prostate (32.9%) or breast (19.4%) cancer, with many (47.1%) diagnosed