Main Session
Sep
29
PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care
3611 - Repeat Lung Stereotactic Radiation for Non-Small Cell Lung Cancer: A Single-Institution Retrospective Study
Presenter(s)
Daniel Schep, MD, MS - Juravinski Cancer Centre, Hamilton, ON
D. Schep1,2, D. M. Palhares1,3, G. J. Li1,2, A. Karotki1,3, and A. V. Louie1,3; 1Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada, 2Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada, 3Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada
Purpose/Objective(s):
The safety and efficacy of stereotactic body radiation therapy (SBRT) for non-small cell lung cancer (NSCLC) in the setting of prior thoracic radiation remain poorly defined. This study aims to assess the feasibility, safety, and effectiveness of reirradiation in NSCLC patients.Materials/Methods:
In this health research ethics board approved study, patients treated at our institution who received at least 2 courses of SBRT to the lung for NSCLC were retrospectively reviewed. Patients were included if there was overlap in the 50% isodose lines in at least 2 courses. Radiation treatments in the thorax with at least 3 months of clinical follow up were included in a dose accumulation, wherein CTs and dose distributions were deformed onto the CT used for the most recent lung SBRT treatment. Before summation all dose distributions were converted into 2Gy per fraction equivalent (EQD2). Toxicity was recorded using the Common Terminology Criteria for Adverse Events (CTCAE) criteria. Descriptive statistics were generated to summarize demographics, retreatment details, and toxicities. A cumulative incidence function was used to calculate the incidence of locoregional failure (LRF) with death as a competing risk. Kaplan-Meier estimators were used to calculate progression free survival (PFS) and overall survival (OS). Predictors for any toxicity were assessed using a univariable logistic regression model.Results:
Thirty-five patients were included and received a median of 3 (2-5) radiation courses, of which 99 (94.3%) were SBRT and 6 (5.7%) were fractionated. Thirty patients (85.7%) had stage I disease, and 5 (14.3%) had stage IV. The most common dose was 48Gy in 4 fractions for both initial SBRT and first retreatment. The median time to first re-irradiation was 20.4 months (4-50.4 months). The indication for first re-irradiation was second primary, locoregional recurrence, and distant metastasis in 21 (60%), 9 (25.7%), and 6 (17.1%) cases, respectively. The 12-month LRF, PFS, and OS rates after first re-irradiation were 31.4%, 45.7%, and 68.6%, respectively. The median cumulative lung V20Gy, D1500cc, and Dmean were 16.1% (7.7-59.4%), 3.7Gy (0.2-15.4Gy), and 13.2Gy (6.4-43.9Gy), respectively. The median cumulative esophageal D5cc was 21.9Gy (3.1-80Gy). Grade 2 and 3 toxicities were observed in 9 (25.7%) and 3 (8.6%) cases, respectively, with a single case each of grade 3 dyspnea, chest wall pain, and esophageal stricture observed. Esophageal D5cc was the only significant predictor of any toxicity (OR 1.04, p=0.046).Conclusion:
Repeat thoracic SBRT is feasible, although ongoing progression remains likely to require yet further radiation courses. While toxicities are acceptable, additional studies are required to determine dosimetric thresholds for safety.