P05.13 Central vs Peripheral Thoracic Malignancies Treated with SBRT: Early Outcomes of a Prospective Quality of Life Study

Abstract

Thoracic malignancies in close proximity to central mediastinal structures are known to have a higher rate of treatment-related toxicity following stereotactic body radiation therapy (SBRT). Intrinsic damage secondary to tumor invasion may contribute to this increased toxicity and could be identified by pretreatment quality of life metrics. The appropriate dose fractionation schedule as well as daily treatment schedule that may mitigate the aforementioned central toxicity remains nebulous. We reviewed patients on a prospective trial assessing quality of life before and after SBRT and stratified based on central versus peripheral anatomical location. In this single institutional study, patients were enrolled on a prospective quality of life trial approved by the local Institutional Review Board. All patients were evaluated by a multidisciplinary thoracic oncology team and were diagnosed with thoracic malignancy amenable to stereotactic body radiation therapy delivered in 5 or fewer treatment fractions on an every other day schedule. Central tumors were defined as those within 2 cm of central mediastinal structures including the proximal bronchial tree. Patients underwent pre-and post-treatment quality of life questionnaires including the prospectively validated EORTC Quality of Life Core questionnaire (QLQ-C30 version 3) and Supplemental Lung Cancer module questionnaire (QLQ-LC13). Baseline differences between groups were analyzed using the Mann-Whitney U and Chi-squared tests. Score comparisons for EORTC questionnaires pre- and post- SBRT were conducted using the Wilcoxon signed-rank test. All statistics were performed in SPSS, version 24. A total of 31 patients from February 2018 to February 2020 were enrolled with a median age of 70 (59-90) years. The majority of patients had an ECOG of 1 (n = 15) and the most common histology was adenocarcinoma (n = 17). A total of 13 patients were found to have central lung tumors. There were no significant pretreatment differences in age, performance status, gender or the predefined EORTC questionnaire-specific subcategorized functional, quality of life, or symptom domains between patients diagnosed with central versus peripheral tumors. Following SBRT, there were notable, statistically significant improvements in the Emotional functioning (EF) domain (pre- and post- treatment median: 61.5 and 91.7, respectively, z=-2.01, p=.044) and the Cognitive functioning (CF) domain (pre- and post- treatment median: 75.0 and 91.7, respectively z=-2.06, p=.039) in patients treated for central lung tumors. Similar improvements were not observed in patients treated for peripheral lung tumors. There were no significant changes in any other functional, symptom, or quality of life domain following treatment for either group. Pretreatment EORTC quality of life metrics did not demonstrate significant differences in patients diagnosed with central versus peripheral thoracic malignancies in our prospective cohort. However, patients with central lung tumors experienced significant improvements in their EF and CF domains following SBRT. These findings suggest patients with central lung tumors may experience greater psychological distress from their disease independent of self-reported physical symptom burden.