Limited Stage Small Cell Lung Cancer Patients With Complete Response After Thoracic Chemoradiotherapy Still Benefit From Prophylactic Cranial Irradiation in the MRI Era

Abstract

Currently prophylactic cranial irradiation (PCI) is recommended for limited stage small cell lung cancer (LS-SCLC) patients with good response after thoracic chemoradiotherapy. However, the role of PCI for LS-SCLC was doubted after Japanese study published, which PCI was not superior to magnetic resonance imaging (MRI) follow up for extensive stage of SCLC. This study was aimed to investigate the role of PCI for LS-SCLC in the MRI era.We retrospectively evaluated patients with LS-SCLC who without brain metastasis (BM) confirmed by MRI, and had complete response (CR) or partial response (PR) after initial chemoradiotherapy in our Center between 2007 and 2018. The overall survival (OS), progression-free survival (PFS), and cumulative incidence of BM were estimated by Kaplan-Meier method between patients received PCI or not.There were 121 patients enrolled in this study. The median age was 59 years old. Ninety-six patients were male, and 25 patients were female. After initial chemoradiotherapy, 55 patients achieved CR, and 66 patients achieved PR. Eighty-six patients received PCI, and 35 patients did not. For the whole group, patients received PCI had lower 2-year BM (10.8% vs 31.9%, P = 0.02), and better median PFS (58.0 [95% CI: 7.4 - 108.6] months vs 18.0 [95% CI: 11.0 - 25.0] months, P = 0.002) than those did not. However, the difference of median OS between two group was not statistically significant (95.0 [95% CI: 56.5 - 133.5] months vs 56.0 [95% CI: 13.8 - 98.2] months, P = 0.08). For the CR subgroup, patients received PCI had lower 2-year BM (8.6% vs 47.1%, P = 0.04), better median PFS (93.0[95% CI: 54.7 - 131.3] months vs 66.0 [95% CI: 0.0 - 141.6] months, P = 0.04), and better median OS (117.0 [95% CI: 85.4 - 148.6] months vs 68.0 [95% CI: 0.0 - 143.3] months, P = 0.049) than those did not. For the PR subgroup, patients received PCI had better median PFS (31.0 [95% CI: 17.0 - 44.9] months vs 16.0 [95% CI: 5.8 - 26.2] months, P = 0.012) than those did not. However, the difference of median OS between two group was not statistically significant (45.0 [95% CI: 28.4 - 61.7] months vs 56.0 [95% CI: 9.2 - 102.8] months, 2-year BM between two group was not statistically significant (12.8% vs 20.6%, P = 0.53).In the MRI era, LS-SCLC patients with CR after thoracic chemoradiotherapy still benefited from PCI. However, PCI should not be recommended to patients achieved only PR after initial treatment.