Radiographic and metabolic response rates following image-guided stereotactic radiotherapy for lung tumors

Abstract

Purpose To evaluate radiographic and metabolic response after stereotactic body radiotherapy (SBRT) for early lung tumors. Materials and methods Thirty-nine tumors were treated prospectively with SBRT (dose = 48–60 Gy, 4–5 Fx). Thirty-six cases were primary NSCLC (T1N0 = 67%; T2N0 = 25%); three cases were solitary metastases. Patients were followed using CT and PET at 6, 16, and 52 weeks post-SBRT, with CT follow-up thereafter. RECIST and EORTC criteria were used to evaluate CT and PET responses. Results At median follow-up of 9 months (0.4–26), RECIST complete response (CR), partial response (PR), and stable disease (SD) rates were 3%, 43%, 54% at 6 weeks; 15%, 38%, 46% at 16 weeks; 27%, 64%, 9% at 52 weeks. Mean baseline tumor volume was reduced by 46%, 70%, 87%, and 96%, respectively at 6, 16, 52, and 72 weeks. Mean baseline maximum standardized uptake value (SUV) was 8.3 (1.1–20.3) and reduced to 3.4, 3.0, and 3.7 at 6, 16, and 52 weeks after SBRT. EORTC metabolic CR/PR, SD, and progressive disease rates were 67%, 22%, 11% at 6 weeks; 86%, 10%, 3% at 16 weeks; 95%, 5%, 0% at 52 weeks. Conclusions SBRT yields excellent RECIST and EORTC based response. Metabolic response is rapid however radiographic response occurs even after 1-year post treatment.