Prophylactic cranial irradiation for limited-stage small-cell lung cancer in the magnetic resonance imaging era.

Background: We investigated the role of prophylactic cranial irradiation (PCI) in limited-stage small-cell lung cancer (LS-SCLC) according to tumor response in the magnetic resonance imaging (MRI) era.

Methods: We retrospectively evaluated patients with LS-SCLC without brain metastases (BMs) on MRI who achieved either complete response (CR) or partial response (PR) after initial chemoradiotherapy at our center from 2006 to 2017.

Results: This study comprised 116 patients (median age, 58 years; men, 92; women, 24). After initial chemoradiotherapy, 53 patients achieved CR, while 63 patients achieved PR. Eighty-three patients received PCI. Patients who received PCI had better overall survival (OS, 5-year: 52.5% vs. 35.1%; p = 0.012) and progression-free survival (PFS, 5-year: 45.0% vs. 28.2%; p = 0.001) and a lower incidence of BMs (5-year: 18.3% vs. 39.4%; p = 0.010). In the subgroup analysis, PCI improved OS (5-year: 67.8% vs. 46.7%, p = 0.005) and PFS (5-year: 65.2% vs. 35.0%, p = 0.021) and decreased BM risk (5-year: 12.1% vs. 52.4%, p = 0.002) for patients with CR. However, PCI had no benefit (5-year OS: 40.5% vs. 35.6%, p = 0.763; 5-year BMs: 24.6% vs. 31.9%, p = 0.561) for patients with PR.

Conclusions: Tumor response remained an important factor for selecting patients for PCI in the MRI era. PCI should be recommended for patients with LS-SCLC who achieve CR after initial thoracic chemoradiotherapy.