Incidence of second cancer within 5 years of diagnosis of a breast, prostate or colorectal cancer: a population-based study.

The objective of this study was to evaluate the risk for cancer patients of developing a new primary invasive cancer. Using data from a French Cancer Registry, we included 14,353 cancer patients (breast, colorectal or prostate cancer) diagnosed between 1989 and 1997. Observed second cancers occurring during the first 5 years after the first cancer were compared with the expected number, based on primary cancer incidence rate, by the standardized incidence ratio (SIR). Breast cancer patients had significantly elevated SIR for contralateral breast cancer (SIR=1.7), kidney cancer (SIR=3.5) and myeloid leukaemia (SIR=8.3). Patients diagnosed with colorectal cancer had significantly elevated risk for small intestine (SIR=10.7) and colorectal cancer (SIR=1.6). Young age at diagnosis of breast and colorectal cancers was associated with risk of a second cancer. After prostate cancer, men had no greater risk of cancer, except for kidney cancer. Our results help to direct attention to regions especially vulnerable to secondary cancers after primary breast or colorectal cancer.