Stereotactic Body Radiation Therapy for Medically Inoperable Stages I and II Non-Small Cell Lung Cancer. Single Institution Retrospective Analysis of Outcomes and Predictive Factors - Abstract
Purpose: This retrospective series aims to report the Brazilian single institutional experience and predictive factors for outcomes in patients with early stage and medically inoperable NSCLC treated with SBRT.
Materials/methods: Retrospective analysis of 82 consecutive patients with NSCLC stages IA – IIA (T1aN0M0 – T2bN0M0), by AJCC 8th edition criteria treated from May 2013 to March 2019 with SBRT. All patients were staged with PET/CT and considered medically inoperable. The median age was 77 years old and median tumor size was 2.2cm. Histological subtype was adenocarcinoma in 54 (65.8%), patients, squamous cell carcinoma (SCC), in 25 (30.5%), and 3 (3.7%), had no biopsy. Fifty and six (68.3%), patients were treated with 48Gy in 4 fractions (BED=105.6Gy10), and 26 (31.7%), with 40Gy in 4 fractions (BED=80Gy10) delivered twice a week. Local recurrence free survival (LRFS), disease free survival (DFS) and overall survival (OS), were estimated by Kaplan-Meier method. BED, histological subtype, age and tumor size were factors analyzed for outcomes. Statistical differences in survival curves were calculated by Long Rank test and the hazard ratios were determined by Cox regression model.
Results: With a median follow up of 25 months, the 3-year LRFS, DFS and OS were 82.8%, 68.4%, and 57.9%, respectively. Patients treated with BED=10.6Gy10 had superior 3-year LRFS (89.9% vs 70.0%; p=0.049) and SCC histological subtype was a negative predictive factor for 3-year LRFS compared with adenocarcinoma (90.8% Vs 55.7%; p=0.023). Tumor size and age were not predictive factors for LRFS, DFS and OS. Patients with adenocarcinoma had better 3-year DFS than those with SCC (75.7% % Vs 40.9%; p=0.014). Any grade of pneumonitis occurred with a median of 11 months after the last fraction of SBRT. RTOG grades 1 and 2 pneumonitis occurred in 36 (43.9%), and 4 (4.9%), patients, respectively. Four (4.9%) patients developed thoracic pain with no rib fracture and one patient developed rib fracture.
Conclusions: Results of this series are similar to the literature and confirm that BED larger than 100Gy10 is more effective for local control than lower level in the treatment of NSCLC with SBRT. Patients with SCC had lower LRFS and DFS compared with those with adenocarcinoma. The radiation dose of 48Gy in 4 fractions was effective and safe for patients with peripheral early stages tumors.