Efficacy of Prophylactic Cranial Irradiation in Early to Mid-stage Small Cell Lung Cancer Patients in the Era of Magnetic Resonance Imaging.

Background: Recent advancements in magnetic resonance imaging (MRI) for staging have highlighted the critical question of the need for prophylactic cranial irradiation (PCI) in managing early to mid-stage small cell lung cancer (SCLC). This study assesses the impact of PCI on overall survival (OS) and intracranial control among patients with stage I-IIB SCLC.

Methods: Data from 148 stage I-IIB SCLC patients treated with thoracic radiation therapy (TRT) at two centers were examined. Patients were categorized based on PCI administration: 63 received PCI, while 85 did not. All underwent pretreatment MRI, achieving at least a partial response to therapy. A 1:1 propensity score matching analysis corrected for potential biases.

Results: Propensity scores were generated to 116 patients, considering patient demographics, disease progression, and treatment methods. Death was included as a competing risk. The 3-year brain metastases (BM) occurrence rate was significantly higher in patients who did not receive PCI (30.0%) compared to those who did (14.8%), however, the difference was not statistically significant (No PCI vs. PCI, hazard ratio [HR]: 2.08, 95% CI [0.93-4.55], P = .07). No significant effect of PCI on OS was observed [PCI vs. No PCI, HR: 0.80, 95% CI (0.45-1.43), P = .45]. A subgroup analysis of stage IIB patients showed a significant increase in BM risk and mortality for those not receiving PCI (No PCI vs. PCI, BM risk HR: 5.85, 95% CI: 1.83-18.87, P = .003; mortality HR: 2.78, 95% CI: 1.14-6.67, P = .02), with less pronounced effects in stages I-IIA.

Conclusion: With modern MRI-based screening, PCI may markedly benefit stage IIB SCLC patients by reducing BM and improving OS after initial sensitive treatment. This benefit does not appear to extend to stage I-IIA patients.