PUB114 Dose-Response Relationship for Safety and Efficacy Using Stereotactic Body Radiation Therapy for Centrally-Located Non-Small Cell Lung Cancer

Abstract

Stereotactic body radiation therapy (SBRT) has become a standard treatment for inoperable peripherally-located early-stage non-small cell lung cancer (NSCLC). However, the role of SBRT for centrally-located lesions remains controversial because of the potentially severe toxicity. This study was to evaluate the dose-response relationship for safety and efficacy using SBRT for centrally-located NSCLC. Eighty patients (56 male and 24 female) with centrally-located NSCLC treated with Cyberknife were enrolled between 2006 and 2015. The primary endpoint was the toxicity. The second endpoints were overall survival (OS), progression-free survival (PFS), local control rate (LC), and pattern of failures. The median age was 71 years (range, 51-85). All included patients were confirmed by histologically and PET-CT or CT. Thirty-seven patients had T1 cancer, 33 had T2a, 9 had T2b and 1 had T3. All patients didn’t perform surgery due to organs dysfunction (38.8%), elderly (26.2%), refusal (23.7%), compromised with central lesions (7.5%), and low PS score (3.8%). The planning target volume (PTV) was constructed by adding a 5-mm margin to the gross tumor volume (GTV). The PTV dose was prescribed with a median 74% (range, 58%-80%) isodose line, which covered at least 95% of the PTV. The median PTV volume was 52.2 mL (range, 2.8-264.5), the median prescription dose was 56 Gy (range, 48-60) in 6 fractions (range, 3-10), and the median BED10 was 102.6 Gy (range, 81.3-151.2). Forty-one and 39 patients received Xsight and synchrony tracking model. Median follow-up was 22.6 months (range, 2.6-68.2). CTCAE v4.0 ≥ Grade 3 toxicities occurred in one patient, who died from radiation pneumonitis. Moreover, the occurrence of stenosis and occlusion in lobe bronchus was significantly related with D1 (p < 0.05) other than D0.1, D0.5, D2, D3, and D5 (all p > 0.05). The median OS, 3-year, and 5-year OS were 37.9 months, 51.7%, and 36.8%, respectively. The 3-year and 5-year cancer-specific OS were 63.6% and 52.5%, respectively. The median PFS, 3-year, and 5-year PFS were 26.1 months, 42.5%, and 25%, respectively. The 1-year and 5-year LC rates were 97.1% and 95.6%, respectively. Nine patients (11.3%) and 31 patients (38.8%) had local and regional recurrence as well as distant metastases, respectively. SBRT is a safe and efficacious treatment strategy for centrally-located NSCLC. We recommended that the prescription dose and fractionation modality were given considering potential toxicity except for the patient’s characteristics. And selected patients may require adjuvant chemotherapy in light of the high rate of distant metastasis.