abstract: Outcomes for Patients who Develop Both Breast and Colorectal Cancer

BACKGROUND: Patients diagnosed with both breast and colorectal cancer are not uncommon and will likely be seen more often as the population ages and treatment modalities improve. Survival outcomes for such patients have not been previously reported.  

METHODS: The 1988-2007 Surveillance, Epidemiology, and End Results data were used to identify women diagnosed with both breast and colorectal cancer. Disease-specific survival rates were compared.  

RESULTS: We identified 4,835 women who were diagnosed with both breast and colorectal cancer. Of these, 2,844 (58.8%) were diagnosed with breast cancer first and 1,807 (37.4%) were diagnosed with colorectal cancer first; 184 (3.8%) had synchronous cancers. At 5 years following the second cancer diagnosis, 163 (3.4%) died of breast cancer and 477 (9.9%) died of colorectal cancer (P < 0.05). Comparing primary site groups between years 1 and 5 after the second cancer diagnosis showed that the relative risk of death from breast cancer declined by 46%, though it did not reach statistical significance (P = 0.24), while it significantly increased by 46% for colorectal cancer death (P = 0.0004). These findings persisted regardless of patient age, stage at diagnosis, or breast tumor histology.  

CONCLUSION: For women diagnosed with both breast and colorectal cancer, the cumulative risk of death at 5 years following the second cancer diagnosis is 3 times more likely to be due to colorectal cancer than to breast cancer. Colorectal cancer specific mortality increases with time, while breast cancer specific mortality decreases with time. Consideration should be given to these findings when discussing prognosis and making treatment decisions.