The Influence of Dosimetric Parameters on Quality of Life for Early Stage Non-small Cell Lung Cancer Patients Treated with Stereotactic Body Radiation Therapy

Abstract

Background: Lung stereotactic body radiotherapy (SBRT) has become a standard treatment option for early stage non-small cell lung cancer (NSCLC) patients who are medically inoperable. The influence of radiation dose/volume parameters on quality of life is not known. Our hypothesis is that clinically meaningful declines in quality of life over time will be associated with increased radiation lung dose/volume parameters. Objectives: To investigate clinical toxicity and quality of life (QOL) outcomes of stage I NSCLC patients after SBRT as a function of radiation dose/volume parameters. Methods: In this IRB-approved study, 55 stage I NSCLC patients who received SBRT (12 Gy x 4) and completed QOL forms were analyzed. Clinical symptoms and QOL were measured at baseline and at 3, 6, 12, 18, 24, and 36 months post-SBRT. Clinical toxicity was graded using the common terminology criteria for adverse effects (CTCAE v4.0). Quality of life was followed using the validated Functional Assessment of Cancer Therapy-Trial Outcome Index (FACT-TOI) instrument. Dosimetric parameters, including the mean lung radiation dose (MLD), and the volume of normal lung receiving \u3e 5, 10, 13 or 20 Gy (V5, V10, V13, and V20) were measured from the radiation treatment plan. Student\u27s t-test and Pearson correlation analyses were used to examine the relationships between radiation lung metrics and clinically meaningful changes in QOL and/or clinical toxicities. Kaplan-Meier method was used to estimate rates of local control (LC), disease free survival (DFS), and overall survival (OS). Results: With a median follow-up of 24 months, the 3 year LC, DFS, and OS were 93%, 65% and 84%, respectively, with 5.5% grade 3 toxicity and no grade 4 or 5 toxicities. Clinically meaningful declines in patient reported QOL (FACT-TOI, lung cancer subscale, physical well-being, and/or functional well-being) post-treatment significantly correlated with increased dosimetric parameters, such as V10, V13, and V20. Conclusions: While lung SBRT is associated with excellent LC and minimal clinical toxicity for early stage NSCLC, clinically meaningful declines in QOL significantly correlated with increasing lung dose/volume parameters. This suggests that further improvements in the techniques of lung SBRT have the potential to further enhance patients\u27 QOL following this treatment