SU-E-T-289: Dose-Volume-Effect Relationships for Lung Cancer Patients Treated with SBRT On a Prospective Protocol

Abstract

Purpose: Stereotactic body radiotherapy (SBRT) is commonly used to treat early stage lung tumors. This study was designed to evaluate associations between dose, volume and clinical outcomes including analysis of both clinical toxicity scores and quality of life (QOL) data for non‐small cell lung cancer patients treated with SBRT. Preliminary results are presented. Methods: Sixty‐seven NSCLC patients, 46 primarily with early stage, and 21 with recurrent disease were treated with dose regimens consisting mainly of 12 Gy × 4 fractions, and 3 or 5 fractions at lower dose, for patients with recurrent disease (Table 1). Follow‐up data is being collected at baseline, after treatment and at 3, 6, 12, 18 and 24 months post‐treatment. Clinical follow‐up data acquired to date was assessed using the Charlson Comorbidity Clinical and Toxicity Scoring forms. QOL data was evaluated using the EQ‐5D, and FACT‐TOI validated surveys. All outcomes surveys are collected within an “in‐house” developed outcomes database. Results: The median follow‐up was 3.5±0.8 months. Mean lung doses (MLD) were converted to BED‐2 Gy using the linear‐quadratic model with an alpha/beta=3.0. Average MLD was 3.7+3.1 Gy (range: 0.4–20.9 Gy). The percentages of patients with > grade 2 cough, dyspnea and fatigue were 13.3, 17.0, 6.3%, respectively. Preliminary analyses (at 3 months after SBRT) show a mild correlation between MLD > 2 Gy and > grade 2 cough (borderline significant) and dyspnea (significant, p<0.05). One patient was observed with a grade 3 cough. Given the short follow‐up, tumor control is not yet assessable. Conclusion: The SBRT dose fractionation regimen of 12 Gy × 4 was well tolerated at early time points. Additional follow‐up is required to assess the long‐term clinical outcome efficacy and toxicity profiles of the dose regimen.

Simple Factors Associated With Radiation-Induced Lung Toxicity After Stereotactic Body Radiation Therapy of the Thorax: A Pooled Analysis of 88 Studies

“…This pooled analysis did not show a significant correlation of BED10 with either G2+ or G3+ RILT. This may be partially explained by the fact that here, BED10 specifically represents the dose to tumor instead of the normal lung, which has α/β of 3-4 Gy (33,34), which would generate different values of BED. Further, for highly conformal SBRT, the prescription dose does not necessarily correlate with the dose distribution in normal lung, which depends upon target volume, location and conformity.…”