(P058) Stereotactic Body Radiotherapy for Non–Small-Cell Lung Cancer Patients With Central Lung Tumors: An Analysis of Outcomes and Toxicity

Benjamin Mou, MD, Kenneth W. Merrell, MD, Dawn A. Owen, MD, PhD, Katy Nelson, RN, Yolanda I. Garces, MD, Kenneth R. Olivier, MD; Mayo Clinic

Background: Stereotactic body radiotherapy (SBRT) is increasingly used as the primary treatment for early-stage medically inoperable non–small-cell lung cancer (NSCLC). Although the role of SBRT is established in the treatment of peripheral lung tumors, the outcomes and toxicities of SBRT for central lung tumors are not well characterized. This study investigates our institutional experience with SBRT for central tumors in NSCLC patients.

Materials and Methods: The Mayo Clinic SBRT database prospectively collects patient demographic and treatment-related data for all patients treated at our institution. We performed a retrospective chart review on NSCLC patients with primary and recurrent central lung tumors treated with SBRT between April 2008 and May 2013. The most frequently used dose fractionation regimens were 50 Gy in five fractions and 48 Gy in four fractions delivered over consecutive days. Local control (LC) and overall survival (OS) were measured using Kaplan-Meier estimates. Tumor response was scored using Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1). Toxicity was graded using the Radiation Therapy Oncology Group (RTOG) Common Toxicity Criteria.

Results: A total of 85 central lung tumors from 80 patients were included for analysis. Median age was 74 years (range: 40–91 yr), and median follow-up was 19.1 months (range: 3.3–61.0 mo). There were 54 primary tumors and 31 recurrent tumors. Median tumor size was 2.0 cm (range: 0.6–5.5 cm). There were three local failures, resulting in 2-year and 4-year LC rates of 96.6% and 87.8%, respectively. The median survival was 46.1 months. The 2-year and 4-year OS rates were 69.8% and 39.9%, respectively. Rates of complete response, partial response, and stable disease were 29% (n = 25), 53% (n = 45), and 18% (n = 15), respectively. There were 16 patients with grade III or higher pneumonitis, including one grade IV and one grade V toxicity. The patient with grade V toxicity had a 5.5-cm tumor and prior pneumonectomy. There were no grade III or higher acute toxicities. Toxicities were not associated with tumor size, radiation dose, or previous local therapy. Univariate analysis demonstrated no statistically significant differences in LC or OS between primary or recurrent tumors, histology, tumor size, or radiation dose.

Conclusions: SBRT provides excellent LC for central NSCLC tumors. Toxicity rates are acceptable; however, appropriate patient selection is imperative, as we await results from prospective trials of SBRT for central lung tumors.