Construction of a nomogram to guide prophylactic cranial irradiation in extensive‑stage small cell lung cancer

Patients with extensive-stage small cell lung cancer (ES-SCLC) have a high risk of brain metastasis (BM). However, to the best of our knowledge, the risk factors for BM remain unclear. The present study aimed to investigate the risk factors and establish a prediction model for BM in patients with ES-SCLC. A total of 156 patients with ES-SCLC who had no BM and achieved a partial or complete response between January 2020 and March 2023 were included. Patients were randomly divided into training (n=109) and validation (n=47) cohorts. Factors associated with BM were assessed in the training cohort. Univariate and Cox multivariate analyses were performed to evaluate patients with ES-SCLC. Cox multivariate analysis identified oligometastasis [hazard ratio (HR), 0.35; 95% CI, 0.14-0.85; P=0.021], sex (HR, 2.48; 95% CI, 1.05-5.85; P=0.038) and baseline adrenal metastasis (HR, 2.85; 95% CI, 1.54-5.21; P<0.001) as independent risk factors for BM. A nomogram model was constructed to predict intracranial progression-free survival (iPFS). The areas under the receiver operating characteristic curves for the 9-, 12- and 18-month iPFS in the training cohort were 0.77, 0.74 and 0.75, respectively. The nomogram prediction and actual validation cohorts demonstrated good agreement. Among the high-risk factors for BM, the overall survival analysis demonstrated that non-oligometastasis and baseline adrenal metastasis were unfavorable prognostic factors. The present nomogram may aid risk assessment for BM in patients with ES-SCLC and guide prophylactic cranial irradiation.