Although T1-T2N0 non-small cell lung cancer can be managed with stereotactic body radiotherapy (SBRT) alone, this management has often been extrapolated to T1-T2N0 small cell lung cancer (SCLC). This secondary analysis of a multi-institutional cohort study investigated whether the addition of chemotherapy and prophylactic cranial irradiation (PCI) improved the outcomes for these patients.

All cases of histologically confirmed T1-T2N0M0 SCLC were obtained from 24 institutions' prospectively collected SBRT databases. The clinical and treatment characteristics, toxicities, outcomes, and patterns of failure were assessed. We used Kaplan-Meier analysis to evaluate the survival outcomes. Univariate and multivariate analyses identified the predictors of outcomes.

From 24 institutions, 76 lesions were treated in 74 patients (median follow-up, 18 months). Chemotherapy and PCI were delivered in 56% and 23% of cases, respectively. The median SBRT dose per fraction was 50 Gy/5 fractions. Patients receiving chemotherapy experienced increased median disease-free survival (61.3 vs. 9.0 months; P = .02) and overall survival (31.4 vs. 14.3 months; P = .02). Chemotherapy independently predicted for better outcomes for disease-free survival and overall survival on multivariate analysis (P = .01). Toxicities were uncommon; 5.2% experienced grade ≥ 2 pneumonitis. Post-treatment failures were most commonly distant (45.8% of recurrences), followed by nodal (25.0%), and elsewhere in the lung (20.8%). The median time to each was 5 to 7 months.

Patients undergoing primary SBRT for T1-T2N0 SCLC should also undergo additional chemotherapy. No established role was found for PCI in this population.