Outcomes of Stereotactic Body Radiotherapy for T1-T2N0 Small Cell Carcinoma According to Addition of Chemotherapy and Prophylactic Cranial Irradiation: A Multicenter Analysis

T1-T2N0 small cell lung cancer (SCLC) is rare but is often treated with stereotactic body radiotherapy alone, similar to the treatment of T1-T2N0 non-SCLC. This secondary analysis of a multicenter study assessed whether additional chemotherapy or prophylactic cranial irradiation improves the outcomes. Chemotherapy improved disease-free survival. The use of prophylactic cranial irradiation was not significantly associated statistically with outcomes. These results suggest that T1-T2N0 SCLC should be treated as limited-stage SCLC with no clear indication for prophylactic cranial irradiation. Background 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. Materials and Methods 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. Results 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. Conclusion Patients undergoing primary SBRT for T1-T2N0 SCLC should also undergo additional chemotherapy. No established role was found for PCI in this population.