Prophylactic Cranial Irradiation (PCI) vs. Active Surveillance in Patients with Limited-Stage Small Cell Lung Cancer: A Retrospective, Multicenter study

Abstract

<h3>Purpose/Objective(s)</h3> The recommendation of PCI for limited-stage small cell lung cancer (LS-SCLC) with good response to chemoradiotherapy is primarily based on the evidence from the pre-magnetic resonance imaging (MRI) era. However, as the MRI fidelity improves and stereotactic radiosurgery advances, the role of PCI for LS-SCLC becomes uncertain. This study aims to compare the contemporary survival outcomes of PCI versus active surveillance in patients with LS-SCLC. <h3>Materials/Methods</h3> We conducted a retrospective cohort study in which 1068 patients with LS-SCLC who achieved good response to first-line chemoradiotherapy were consecutively enrolled from 5 tertiary hospitals between June 2009 and June 2019. Of these, 440 patients received PCI while 628 received active surveillance with PCI omission. Propensity score matching in a 1:1 ratio with a caliper of 0.2 was performed to balance baseline characteristics of the two groups. The endpoints of this study were overall survival (OS) and the incidence of brain metastases (BM). <h3>Results</h3> In total, 324 LS-SCLC patients with PCI were matched to 324 with active surveillance. Baseline characteristics were generally well balanced between the two matched groups. At a median follow up of 64.5 months (range 2-190), patients with PCI had a significantly lower risk for BM than those with active surveillance. The 3-year cumulative incidence rate of BM was 28.2% (95% CI 22.5%-33.8%) in the PCI group and 38.5% (95% CI 32.6%-44.5%) in the surveillance group (Gray's <i>p</i>=0.002). However, the lower incidence of BM in the PCI group did not translate into a significant extension of OS. The median OS was 35.8 months (95% CI 27.6-44.0 months) in the PCI group versus 32 months (95% CI 26.4-37.6 months) in the surveillance group (HR 0.90, 95% CI 0.74-1.10, <i>p</i>=0.29). <h3>Conclusion</h3> Collectively, PCI reduces the risk for BM but did not substantially prolong OS compared with active surveillance. A Phase 3, prospective clinical trial (NCT04829708) we initiated is currently underway, which is expected to corroborate our results.