Research has found that trigger tools perform poorly in cancer care. This cohort study comprised of adult patients undergoing treatment for breast, colorectal, lung or prostate cancer investigated the feasibility of a cancer-specific claims-based trigger tool to identify patients with potential adverse events. Results found that triggers affected 19% of patients during their initial year in treatment, and that trigger burden varied by disease, stage, and patient demographics. The most prevalent triggers were abnormal lab test results, blood transfusions, orders for non-contrast CT after chest radiation, and hypoxemia.