Change of bone mineral density as a prognostic marker in small cell lung cancer treated with immune checkpoint inhibitors: a multicenter retrospective study.

Background: Changes in bone mineral density (BMD) are recognized as an independent predictor of survival in a variety of diseases. However, the prognostic value of BMD in small cell lung cancer (SCLC) patients treated with immune checkpoint inhibitors (ICIs) is not well understood. This study aimed to explore the prognostic ability of change in bone mineral density (ΔBMD) on the survival of SCLC patients receiving ICIs.

Methods: A total of 300 SCLC patients receiving ICIs from three hospitals were enrolled and underwent non-enhanced thoracic computed tomography (CT) before and after treatment. Overall survival (OS) and progression-free survival (PFS) were analyzed using Cox regression models and Kaplan-Meier survival curves. A nomogram model based on independent prognostic factors was developed using multivariate Cox proportional hazards analysis. The predictive efficacy and clinical benefit of the nomogram were evaluated using the time-dependent area under the receiver operating characteristic (ROC) curve and calibration curves.

Results: Lower ΔBMD was associated with shorter PFS and OS. ΔBMD was identified as an independent prognostic factor affecting OS (risk ratios =0.461; P<0.001). The established nomogram resulted in the area under the ROC curve for OS at 9, 12, and 18 months of 0.743, 0.782, and 0.781, respectively. The C-index was 0.701 [95% confidence interval (CI): 0.663-0.739], and the calibration curves confirmed that predictions aligned well with actual observations.

Conclusions: Lower ΔBMD is correlated with poorer clinical outcomes in SCLC patients undergoing treatment with ICIs.