Toxicity Profile for Connective Tissue Disease Patients Treated with Lung Stereotactic Body Radiation Therapy (SBRT)

Abstract

<h3>Purpose/Objective(s)</h3> Connective tissue diseases (CTDs) have historically been considered as presenting contraindications to radiotherapy (RT), in particular lung RT, due to concern for increased rates of severe toxicity. Improving medical management of CTDs may lead to an increasing number patients with CTDs requiring lung RT. As a subset of lung RT, stereotactic body radiation therapy (SBRT) used for inoperable early-stage lung cancer or oligometastases is associated with very low rates of high-grade toxicity. The present study seeks to detail the safety of lung SBRT in CTD patients. <h3>Materials/Methods</h3> A single institution prospective lung SBRT registry was surveyed for all patients treated for primary cancer, oligometastasis or salvage from 2006 – 2021. Tumors were identified as peripheral or central per RTOG criteria. Treatment-related toxicity was graded per CTCAE version 3.0. Medical management of CTDs was recorded at time of cancer consultation. <h3>Results</h3> A total of 91 CTD patients undergoing 122 courses of lung SBRT were available for analysis. Median age of the cohort was 72 years (64 – 80, IQR) comprised of 27 (30%) males and 64 (70%) females. Median KPS was 80 (70 – 90, IQR). Median follow-up was 20 months (8 – 42, IQR). CTD patients included 43 (47%) with rheumatoid arthritis (RA), 14 (15%) with systemic lupus, 18 (20%) with CTD associated interstitial/idiopathic lung disease, 5 (6%) with scleroderma, and 37 (41%) with other CTDs. Thirty-five (38%) patients had multiple CTDs. At SBRT, 47 (52%) patients were on active medical treatment and two (2%) had prior lung transplantation. For a range of fractionation schedules, SBRT median BED₁₀ was 106 Gy (100 – 149, IQR). Nine (10%) patients were treated with synchronous lesions, with two (2%) patients receiving five simultaneous treatments for oligometastatic disease. Twenty-six tumors (21%) were central. Median tumor size was 1.7 cm (1.2 – 2.7, IQR). Overall, 25 (21%) treatments resulted in grade 2 and greater toxicity, with four (3%) grade 3 and no grade 4 or 5 toxicities. Lung toxicities included 12 (10%) pneumonitis, 10 (8%) chest wall pain, 2 (2%) cough, and 1 (1%) pleural effusion. Grade 3 pneumonitis rate was 10% for CTD associated interstitial/idiopathic lung disease, 2% for RA, and 0% for lupus and scleroderma. <h3>Conclusion</h3> Lung SBRT for CTD patients was not generally associated with increased rates of high-grade toxicity but on subset analysis, patients with CTD associated interstitial/idiopathic lung disease may be at risk for grade 3 pneumonitis.