R. Roden1, W. S. Harmsen2, W. Breen3,4, K. Olivier3, Y. Garces3, S. S. Park3, K. W. Merrell3, J. N. Sarkaria3, and D. Owen3; 1Mayo Clinic Alix School of Medicine, Rochester, MN, 2Mayo Clinic Rochester, Rochester, MN, 3Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 4Mayo Clinic, Rochester, MN
Purpose/Objective(s): Interstitial lung disease (ILD) increases the risk for life threatening pulmonary complications in patients treated with definitive radiotherapy. We report our early oncologic outcomes and adverse events (AEs) for intensity modulated proton therapy (IMPT) for patients with ILD and primary lung cancers. Materials/
Methods: Between 2017 and 2023, 37 patients with ILD aged > 18yrs and who received definitive chemoradiotherapy (CRT) or stereotactic body radiation (SBRT) with IMPT were retrospectively reviewed. Baseline demographics, pulmonary function tests, dosimetric factors, and outcomes were collected. Overall survival (OS) and disease-free survival (DFS) were estimated using the Kaplan-Meier method. Adverse events were graded by CTCAE v5.0. Results: Median age of our cohort was 71.3 years (R: 37.9-91.4), and 23 pts were male. Median smoking history was 30 pack/years (R: 0-70), and 56.4% patients were = Stage IIA. 23/37 (62.2%) patients had prior chest RT with median a prior RT dose of 60 Gy. 32/37 (86.2%) patients were on oxygen at baseline. Median percent predicted DLCO prior to IMPT was 44% (R: 31-75) and post IMPT was 36% (R: 24-67). Median absolute FEV1 and FVC pre IMPT were 1.7 L (R: 1.1-3.5) and 2.5 L (R: 1.2-4.7) and post IMPT were 2.0 L (R: 1.0-3.1) and 2.7 L (R: 1.2-4.7). IMPT physical dose (RBE 1.1) ranged from 40-60 Gy in 4-30 fractions. 58.8% of patients received chemotherapy. 26/37 patients received SBRT or hypofractionated IMPT. Of the 33 patients with a biopsy, 12 had squamous cell carcinoma (36%), 15 had adenocarcinoma (45%), and 2 (6%) were small cell lung cancer. Median lung V20 from the SBRT plans was 6.9% (R:0.8-27.8) and 10.6% (0.6-30.1) for the CRT plans. Median CTV volume (cc) was 137 cc (4.5-999). With a median follow up for surviving patients of 81 months (R: 1.4-4.9), 34 pts had evaluable imaging after treatment. At the time of analysis, 21/34 patients were deceased. 6 patients succumbed to respiratory failure/pneumonia. Cancer related deaths occurred in 10 patients. OS at 1 and 2 years were 69.4% and 42.8. DFS at 1 and 2 years were 54.9% and 33.4%. Seven patients (19%) had = grade 2+ pneumonitis [grade 2 (4) and grade 3 (3)]. One patient terminated IMPT early (chemoradiation) secondary to a grade 3 tension pneumothorax from bronchopleural fistula due to cancer/radiation. Conclusion: Definitive proton radiotherapy appears to be safe in patients with interstitial lung disease, even in a reirradiation scenario.
