Paul S, et al. Int J Radiat Oncol Biol Phys 2020.
PURPOSE: Many lung cancer patients are inactive due to their disease and underlying comorbidities, and activity levels can decline further during cancer therapy. Here we explore dosimetric predictors of activity decline in a cohort of patients who underwent continuous activity monitoring during definitive concurrent chemoradiotherapy (CRT) for locally advanced lung cancer.
METHODS AND MATERIALS: We identified patients who participated in prospective clinical trials involving the use of a commercial fitness tracker throughout the course of CRT. For each subject, we applied linear regression to log-transformed daily step counts to compute the weekly rate of activity change from one week before radiotherapy [RT] initiation to two weeks after RT completion. Clinical and dosimetric factors were tested as predictors of activity change using linear regressions.
RESULTS: Forty-six subjects met eligibility criteria. Median age was 66 years (range 38-90). Pre-treatment ECOG performance status [PS] was 0, 1 and 2 for 17%, 70% and 13% of the subjects, respectively. Mean lung dose ranged from 5.0 to 23.5 Gy, mean esophagus dose 1.1 to 39.6 Gy, and mean heart dose 0.6 to 31.5 Gy. Median daily step count average before RT was 5861 (IQR: 3540 to 8282) and two weeks following RT completion was 3422 (IQR: 2364 to 5395). Rate of activity change was not significantly associated with age, PS, or mean RT dose received by lungs or esophagus. In multivariate analysis, mean heart dose was significantly associated with rate of activity decline, with a 3.1% reduction in step count per week for every 10 Gy increase in mean heart dose (95% CI: 0.5 to 5.7, p=0.023).
CONCLUSION: Extent of cardiac irradiation is associated with the rate of physical activity decline during CRT for lung cancer. Our novel finding contributes to the growing body of evidence that adverse effects of cardiac irradiation may be manifested at early time points.