Survival of patients with colorectal carcinoma: effect of prior breast cancer.

Abstract
We assessed the combined effect of breast cancer as the first primary tumor and colorectal cancer as the second primary tumor on patient survival in an unbiased way. A new model-based method was employed to control for the expected excess mortality related to the first cancer. The few appropriate previous survival studies (1-7) have been encountered by methodologic problems. The time interval from the first to the second diagnosis was considered in only two studies (7,8). In one small study (9), the survival of patients with colorectal cancer and previous extracolonic primary tumors was better than that of those with no previous tumors.