Competing risk analysis of cancer-specific mortality and postoperative recurrence in SEER-reportable basal cell carcinoma

Basal cell carcinoma (BCC) occurring at Surveillance, Epidemiology, and End Results (SEER)-reportable sites (primarily the lip and external genitalia) represents a distinct subset that is systematically captured in cancer registries, since most cutaneous BCCs are not reportable. This study aimed to identify prognostic factors for cancer-specific death and postoperative recurrence in this SEER-reportable BCC cohort using a competing risk model. Patients with SEER-reportable BCC were identified from the SEER database. Cumulative incidence functions were used to estimate and visualize the time-dependent probabilities of cancer-specific death and postoperative recurrence, and Gray’s tests were applied for univariable group comparisons. Multivariable Fine–Gray models were then employed to assess potential independent prognostic factors. Recurrence was indirectly inferred from subsequent records in SEER. About 25% of recurrence times were missing and addressed by multiple imputation, with sensitivity analyses confirming robustness. Among 2,753 and 2,052 patients included for cancer-specific death and postoperative recurrence analyses, 69 deaths (2.5%) were attributed to BCC, while 32 cases (1.6%) experienced recurrence after surgery. Multivariable Fine–Gray models identified age, sex, marital status, pathological subtype, summary stage, and chemotherapy as independent predictors of cancer-specific mortality; though this likely reflects confounding by indication (chemotherapy reserved for advanced disease). For postoperative recurrence, an exploratory analysis with limited events suggested that residential area was a potential independent factor. Using a competing-risk approach, this study identified predictors of cancer-specific death and, in an exploratory analysis, potential factors for postoperative recurrence in SEER-reportable BCC, providing preliminary evidence for risk stratification within this registry-defined population.