Prophylactic Cranial Irradiation in Patients with Limited-Stage Small-Cell Lung Cancer without Brain Metastases: A Retrospective Cohort Study

Abstract

<h3>Purpose/Objective(s)</h3> Previous studies showed that prophylactic cranial irradiation (PCI) reduced brain metastases and improved overall survival of patients with limited-stage small-cell lung cancer (LS-SCLC). However, brain magnetic resonance imaging (MRI), currently recognized as the preferred modality for brain metastases detection, was not routinely used for staging and reassessment in previous trials. This retrospective study aimed to reevaluate the role of PCI for LS-SCLC patients in the modern MRI era. <h3>Materials/Methods</h3> We retrospectively reviewed LS-SCLC patients treated with definitive chemoradiotherapy (≥4 cycles of chemotherapy and thoracic intensity-modulated radiotherapy [IMRT]) between 2006 and 2014 in our center. Patients who responded to initial therapy were included and subsequently reassessed for brain metastases by MRI. The cumulative incidence of brain metastases was estimated using the Fine-Grey competing risks regression model. The overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method. Univariate and multivariate analyses were performed using the Cox proportional hazards model. <h3>Results</h3> We enrolled 177 patients in this study, of which 79 were treated by PCI and 98 were not (non-PCI). The median follow-up was 76.0 months (95% confidence interval, 71.2-80.8 months). All patients achieved complete response (<i>n</i> = 50, 28.2%) or partial response (<i>n</i> = 127, 71.8%) to initial chemoradiotherapy. The cumulative incidence of brain metastases in the PCI group was lower than in the non-PCI group (6.6% vs. 30.0% at 2 years, 12.2% vs. 31.0% at 5 years, <i>P</i> = 0.004). 5-year PFS in the PCI group was significantly higher than in the non-PCI group (45.3% vs. 26.5%, <i>P</i> = 0.002). However, 5-year OS of 48.8% and 39.2% in the PCI and non-PCI groups, respectively, were similar (<i>P</i> = 0.255). In the multivariate analysis, treatment response (<i>P</i><0.001) and PCI (<i>P</i> = 0.038) were independent prognostic factors for PFS. Stratification analysis revealed that PCI did not improve 5-year PFS for patients with partial response to initial therapy (26.6% vs. 19.7%, <i>P</i> = 0.234). <h3>Conclusion</h3> In the Modern Era with MRI Surveillance, PCI is associated with a lower incidence of brain metastases and improved PFS while OS benefit wasn't observed. Patients achieving partial response to initial therapy did not gain PFS benefit from PCI. Prospective trials are still needed to further evaluate the utility of PCI for patients with LS-SCLC.