Key PointsQuestionWhat is the relative burden of oncologic and nononcologic mortality among long-term survivors of cancer in the US?FindingsIn this cohort study of 627 702 patients surviving 5 years or more from an initial diagnosis of early-stage breast, prostate, or colorectal cancer, the risk of dying from the index cancer varied widely relative to noncancer-specific causes of death. Patients with low oncologic risk at the time of diagnosis had at least 3-fold higher risk of noncancer death compared with death from the index cancer.MeaningThis study suggests that risk-stratified care may help quantify the relative importance of oncologic and primary care surveillance for long-term survivors of cancer.