Temporal Dynamics and Heterogeneity of Cancer-Specific and Cardiovascular Mortality in Adult Cancer Survivors: A SEER-Based Competing Risks Analysis

Background: Advances in cancer detection and treatment have extended survival, creating a growing population at risk for competing causes of mortality. Cardiovascular disease (CVD) is a leading competing cause, yet the comparative dynamics of cancer-specific and cardiovascular mortality across cancer types and demographics remain unclear. Methods: We analyzed 487,619 adults with first primary malignancies from the SEER 17 Registries (2000–2019). Cause-specific mortality was examined using Kaplan-Meier survival and cumulative incidence functions (CIF) to account for competing risks. Fine-Gray competing risks regression assessed age, sex, and cancer site effects on cancer-specific and cardiovascular mortality. Results: Over median 79 months, CVD mortality exceeded cancer mortality from diagnosis with no crossover. At 12 months, CIF for CVD death was 6.62% vs 0.24% for cancer death; at 60 months, CVD death rose to 20.75%, cancer death remained 0.40%. Females had an 18% higher cancer death risk but 28% lower CVD death risk vs males (p < 0.001). Colorectal cancer carried the highest cancer death risk; lung cancer had the highest CVD death risk (p < 0.001). Age was strongly linked to CVD but not cancer mortality. Conclusions: CVD is the dominant competing cause of death in adult cancer survivors, highlighting urgent need for integrated cardio-oncology care. Targeted cardiovascular risk reduction alongside oncologic management is essential to improve long-term outcomes and survivorship quality.