Efficacy and Toxicity of Stereotactic Body Radiation Therapy Treatment of Multiple Lung Lesions

Abstract

<h3>Purpose/Objective(s)</h3> As the role of SBRT in caring for patients with complex cancer presentations continues to expand, it is paramount to elucidate how many courses of lung SBRT are safe and what factors predict toxicity. Our study seeks to evaluate the dose-volume factors and associated toxicities for treatment of multiple lung tumors with SBRT. <h3>Materials/Methods</h3> This retrospective IRB approved study was conducted using our institutional database of patients who underwent SBRT for multiple lung lesions between 2012 to 2020. 64 patients underwent SBRT for multiple tumors for a total of 137 tumors treated. We compared dosimetry and clinical outcome parameters of these patients to a paired set of 50 randomly selected patients who received SBRT for a solitary lung lesion. Variables collected include patient age, gender, cancer stage, tumor histology, SBRT dose, dosimetric parameters, toxicities from SBRT, and progression-free survival (PFS). Acute toxicity was defined as any toxicity related to lung SBRT occurring <90 days from the start of SBRT and late toxicity was beyond 90 days from the end of SBRT. Statistical analysis was performed using statistical software. <h3>Results</h3> 137 pulmonary lesions in 64 patients (2+ lesions in every patient) were treated using SBRT at our institution. Of these 137 lesions, 122/137 (89.1%) were primary lung tumors and 15/137 (10.9%) were metastatic lesions. Out of the 137 lesions, 9.5% were classified as SCLC, 43.1% as adenocarcinoma, 36.5% as squamous cell carcinoma, and 10.9% as distant metastases. The mean prescription dose for multi-lesion patients was 50 Gy delivered in 3-5 fractions versus 50 Gy in 5 fractions in the single lesion group. The mean V5 (47.3% vs. 25.7%, p<0.05), V10 (26.8.3% vs. 15.4%, p<0.05), V20 (10.2% vs. 4.5%, p<0.05), and mean lung dose (10.05 Gy vs. 5.29 Gy, p<0.05) were significantly greater in multi-lesion patients compared to single lesion patients, respectively. Fatigue and dyspnea were the most commonly reported acute toxicities; 56.2% multi-lesion patients experienced fatigue and 18.8% experienced dyspnea while 22.0% of single lesion patients experienced fatigue and 12.0% experienced dyspnea (p=0.315). No late toxicities were documented. 126/137 (92.0%) of the lung lesions treated with multiple SBRT treatments demonstrated local control, while 11/137 (8.0%) had local recurrence. 1-year PFS was 92.2% in the multi-lesion group versus 84.0% in the single lesion group. There was no significant correlation between pulmonary toxicity and histology in the single lesion and multi-lesion groups. <h3>Conclusion</h3> Our results suggest that SBRT treatment of multiple pulmonary tumors is safe and feasible without increasing in acute or late pulmonary toxicity. While there is significant difference in all lung parameters between these two groups, it did not translate into increasing toxicity. Further studies are needed to understand the relation between radiation dose parameters and incidence of pulmonary toxicity.