Objective:To investigate the effects of estimated dose of radiation to immune cells (EDRIC) on overall survival (OS), local progression-free survival (LPFS) and distant metastasis-free survival (DMFS) in limited-stage small-cell lung cancer (LS-SCLC) with different tumor burdens.Methods:Clinical data of 216 patients with LS-SCLC who initially received conventional fractionated radiotherapy of the chest for radical treatment in Tianjin Medical University Cancer Institute and Hospital from 2013 to 2019 were retrospectively analyzed. EDRIC was calculated based on the model developed by Jin et al. and tumor burdens were assessed by gross tumor volume (GTV) or clinical stage. The study endpoints were OS, LPFS and DMFS, which were calculated from the date of diagnosis. The optimal cut-off value of EDRIC was calculated by R language. The correlation between EDRIC and tumor burdens was analyzed using Spearman's correlations. Survival analysis was performed by Cox proportional hazards regression model and Kaplan-Meier curve. Results:The median follow-up time for the whole group was 47.8 months, and the median OS and DMFS was 34.6 months and 18.5 months, respectively, while the median LPFS did not reach. The optimal cut-off value of EDRIC was 6.8 Gy. Cox multivariate analysis showed that EDRIC was an independent prognostic factor affecting OS and DMFS. EDRIC was weakly correlated with GTV or clinical stage. Stratified by the median GTV, OS ( P=0.021) and DMFS ( P=0.030) were significantly shortened and LPFS had a tendency of shortening ( P=0.107) when EDRIC>6.8 Gy compared with those when EDRIC ≤ 6.8 Gy in the GTV ≤ 34.6 cm 3 group; EDRIC had little effect on OS, LPFS, and DMFS ( P=0.133, 0.420, 0.374) in the GTV>34.6 cm 3 group. Stratified by clinical stage, OS ( P=0.003) and DMFS ( P=0.032) were significantly shortened and LPFS ( P=0.125) tended to shorten when EDRIC>6.8 Gy in stage I, II and IIIA groups; EDRIC exerted slight effect on OS, LPFS, and DMFS ( P=0.377, 0.439, 0.484) in stage IIIB and IIIC groups. Conclusion:EDRIC is an important factor affecting prognosis and exerts more significant impact on prognosis in patients with smaller tumor burden.

Objective:To establish a brain metastasis (BM) prediction model for limited-stage small cell lung cancer (LS-SCLC) patients who achieved complete response (CR) or partial response (PR) after thoracic chemoradiotherapy, and to explore the value of prophylactic cranial irradiation (PCI) in different risk groups.Methods:Clinical data of 274 patients with LS-SCLC who achieved CR/PR after thoracic chemoradiotherapy in Tianjin Medical University Cancer Institute & Hospital from January 2010 to December 2021 were retrospectively analyzed, including 144 cases in the PCI group and 130 in the non-PCI group. The nomogram was developed based on variables determined by univariate and multivariate analyses in the non-PCI group. The bootstrap method, receiver operating characteristics (ROC) curve, calibration curve and decision curve analysis (DCA) were employed to evaluate the predictive power and clinical benefits of the model. Patients were stratified into high- and low-risk groups based on risk scores. The brain metastases-free survival (BMFS), progression-free survival (PFS), extracranial progression-free survival (ePFS) and overall survival (OS) were compared between patients with and without PCI in different risk-stratified populations using the log-rank test.Results:The nomogram included five variables: systemic immune inflammation index (SII), lymphocyte-to-monocyte ratio (LMR), pro-gastrin-releasing peptide precursor (ProGRP), neuron-specific enolase (NSE), and blood calcium. The area under the ROC curve (AUC) of the nomogram in predicting 1- and 2-year BMFS was 0.761 and 0.822. In the low-risk group, there was no significant difference in the BMFS ( P=0.374), PFS ( P=0.551), ePFS ( P=0.508) and OS ( P=0.767) between the PCI and non-PCI groups. In the high-risk group, PCI could significantly increase the BMFS ( P<0.001) and PFS ( P=0.022), while there was no significant difference in the ePFS ( P=0.963) and OS ( P=0.632). And propensity score-matching (PSM) analysis showed similar results. Conclusions:PCI does not improve OS in LS-SCLC patients regardless of high or low risk of BM. However, PCI significantly prolong the BMFS and PFS in patients at a high risk of BM.