Prediction of Risk of Metastatic Recurrence for Female Breast Cancer Patients in the Presence of Competing Causes of Death.

Background: To estimate risk of recurrence for women diagnosed with nonmetastatic breast cancer considering the risks of other causes mortality.

Methods: We extend a method based on the diagnosis-metastasis-death pathway to include risks of other causes mortality. We estimate three probabilities as cumulative incidence of: (i) being alive and recurrence-free, (ii) death for other causes before a recurrence, and (iii) recurrence. We apply the method to female breast cancer relative survival from the Surveillance, Epidemiology, and End Results Program registries (2000-2018) data.

Results: The cumulative incidence of recurrence shows a higher increase with more advanced cancer stage and is less influenced by age at diagnosis. At 5 years from diagnosis, the cumulative incidence of recurrence is less than 3% for those diagnosed with stage I, 10% to 13% for those diagnosed with stage II, and 37% to 47% for those diagnosed with stage III breast cancer. The estimates of recurrence considering versus ignoring the risks of dying from other causes were generally consistent, except for older women with more advanced stage, and longer time since diagnosis. In these groups, the net probability of recurrence, excluding the risks of dying from other causes, were overestimated.

Conclusions: For patients with cancer who are older or long-term survivors, it is important to include the risks of other cause mortality as the crude cumulative incidence of recurrence is a more appropriate measure.

Impact: These estimates are important in clinical decision making, as higher competing mortality may preclude the benefits of aggressive treatments.