A Phase II Trial of Primary Tumor SBRT Boost Prior to Concurrent Chemoradiation for Locally-Advanced Non-Small Cell Lung Cancer (LA-NSCLC)

Abstract

Primary tumor failure is common in patients treated with chemoradiation (CRT) for unresectable LA-NSCLC. Stereotactic body radiation therapy (SBRT) yields high rates of primary tumor control in Stage I NSCLC. This trial tested an SBRT boost to the primary tumor prior to the start of CRT to improve primary tumor control (PTC).Patients with LA-NSCLC with primary tumor ≤10 cm were enrolled on a prospective phase II trial testing an SBRT boost in 2 fractions (central 6 Gy x 2, peripheral 8 Gy x 2) immediately followed by standard concurrent CRT (60 Gy in 30 fractions). Patients were staged with PET-CT, brain MRI, and underwent 4D-CT simulation for radiation planning using a customized immobilization device that enabled radiation planning for the sequential delivery of the SBRT boost and conventionally-fractionated radiation from the same CT dataset. Chemotherapy was carboplatin/paclitaxel (C/P) or cisplatin/etoposide. For patients receiving C/P, consolidation C/P for 2 cycles was given at the discretion of the medical oncologist. The trial was later amended to allow for consolidation durvalumab. The primary objective was to estimate PTC rate at 1-year with a hypothesis that the 1-year PTC rate is ≥90%. Secondary objectives were to establish the safety, feasibility, objective response rate (ORR; RECISTv1.1), and rates of regional & distant control, disease-free survival (DFS), and overall survival (OS). Exploratory functional MRI (fMRI) scans before and within the first 30 hrs of the first SBRT fraction were performed in 11 patients.The study enrolled 21 patients (10 male, 11 female), with median age 62 years (range 52-78). 16 patients received 6 Gy x 2 SBRT boost, while 5 patients received 8 Gy x 2 SBRT boost. 18 patients received C/P chemotherapy, of whom 9 patients received consolidation C/P. Six patients received consolidation durvalumab. Median pre-treatment primary tumor size was 5.0 cm (range 1.0-8.3). Median and mean follow-up were17.9 and 20.2 months, respectively. The most common toxicities were fatigue, neutropenia, leukopenia, lymphopenia, anemia, pneumonitis, fibrosis, dyspnea and esophagitis. Five grade 4 toxicities related to treatment occurred [lymphopenia (3), neutropenia (1), and leukopenia (1)], but no grade 5 toxicities related to treatment occurred. ORR at 3 and 6 months was 72.7% and 80.0%. The PTC rate was 100% and 92.3% at 1 and 2 years, respectively. The 2-year regional and distant control were 81.6% and 70.3%, respectively. Disease-free survival and overall survival at 2 yrs were 46.1% and 50.3%, respectively. Median survival was 37.8 months. fMRI detected a mean relative decrease in BOLD signal of -87.1% (P = 0.05).Dose escalation to the primary tumor utilizing upfront SBRT appears feasible and safe. PTC was high and other oncologic endpoints compared favorably with the literature. Through the use of 1 CT simulation dataset, accurate calculation of the planned dose through the 2 sequentially-delivered plans is achievable.