Patients receiving radiotherapy for lung cancer commonly experience treatment-related effects that can reduce daily activity. The APART-LUNG pilot study set out to quantify changes in physical activity during a radiotherapy course by using smartphone-derived step counts. The stated aim was to compare average weekly step counts per smartphone wear-hour between the first and the fifth week of radiotherapy and to explore factors potentially associated with decreased activity.
Twenty patients were enrolled in the study; 19 patients were eligible for analysis. Physical activity was assessed using smartphone recordings, summarized as the weekly mean number of steps per smartphone wear-hour. The analysis compared within-patient values from week 1 (baseline) to week 5 of radiotherapy. In addition to the primary comparison, the study explored associations between changes in step counts and a set of patient characteristics.
The primary endpoint was the within-patient difference in the weekly mean steps per wear-hour between week 5 and week 1. Secondary/exploratory assessments examined whether changes in step counts were associated with: age, sex, performance status, comorbidity, body-mass index (BMI), histology, and concurrent systemic treatment. Reported summary measures included mean ± standard deviation and median with ranges for step counts.
For the 19 analyzed patients, the mean number of steps per wear-hour was 344.3 ± 171.6 in week 1 and 363.5 ± 189.9 in week 5. Median step counts were 318.4 (range 123.3–762.9) in week 1 and 300.3 (range 108.3–704.7) in week 5. The within-patient difference between week 5 and week 1 did not reach statistical significance (p = 0.465). In aggregate, the study did not find a significant decrease in step counts during the radiotherapy course.
Individual patient trajectories showed heterogeneity. Weekly average steps per wear-hour decreased in nine patients, increased in nine patients, and remained almost constant (an increase of three steps) in one patient. This distribution indicates that while some patients experienced declines in activity, an equal number improved, and overall the group mean remained similar across the two time points.
The investigators explored associations between decreases in step counts and clinical or demographic characteristics. No tested characteristic reached statistical significance as a predictor of decreased activity. The largest observed difference in the proportion of patients with decreased steps was related to concurrent systemic treatment: comparing patients without versus with concurrent systemic therapy yielded a 37% difference in the proportion showing decreased step counts. Although this represented the strongest signal among the explored variables, it was not reported as statistically significant in this pilot dataset.
In this pilot cohort, step counts measured via smartphone did not significantly decline between the first and fifth weeks of radiotherapy for lung cancer. Patient-level responses were heterogeneous, with roughly equal numbers showing increases and decreases in activity. No baseline characteristic was identified as a significant predictor of decreased activity; however, concurrent systemic treatment produced the largest observed difference in proportions and is highlighted by the authors as a variable to consider when designing future prospective trials.
Limitations reported in the abstract include the small sample size (20 enrolled, 19 analyzed) and the pilot nature of the investigation; these factors limit statistical power to detect modest associations. The study used smartphone wear-hour normalization to summarize activity, but further methodological details (for example, specifics of smartphone usage adherence or any reminder application employed) were not provided in the abstract. The authors recommend that the potential impact of concurrent systemic therapy on physical activity be considered in future study designs.
Overall, APART-LUNG provides preliminary data indicating that, in this small sample, physical activity as captured by smartphone step counts remained broadly stable during the early-to-mid course of radiotherapy for lung cancer, while suggesting hypotheses (not definitive associations) for future, larger investigations.