Abstract
Despite major advances in cancer treatment, the majority of childhood cancer survivors (CCS) will continue to experience cancer treatment-related side effects. Pulmonary dysfunction is a major late effect that can be worsened by respiratory muscle dysfunction. Inspiratory muscle training (IMT) is a possible solution, but CCS may be less responsive to training compared to healthy, typically developing, non-cancer controls (HTD). In this exploratory study, we investigated the effects of 6-weeks of IMT [5 sets of 6 breaths, 5 days per week, at 75% of maximal inspiratory pressure (MIP)] in a home-based setting with weekly monitoring in 7 CCS and 10 HTD, aged between 6 and 12 years. Diaphragm structure and function as well as exercise tolerance were measured before (T1) and after training (T2). Diaphragm thickness at total lung capacity, measured via ultrasonography, improved in CCS [T1 vs. T2: +0.05, 95% confidence interval: (0.01, 0.1) cm, P = 0.02], but not in HTD. Whereas chest wall excursion (CWE) and performance on the 6-minute walk test (z-score) improved in HTD [T1 vs. T2 CWE: +0.81 (0.23, 1.39) cm, P < 0.001; T1 vs. T2 6MWT z-score: +0.49 (0.23, 0.75), P < 0.001], but not in CCS. Respiratory muscle performance, measured by MIP (% predicted) and muscle quality, defined as the ratio of MIP (cmH(2)O) to diaphragm thickness, improved in both groups (P < 0.05 for all). Thus, we provide preliminary findings suggesting that there might have been differences in the response to training due to cancer treatment-related late effects in CCS. However, these findings should be interpreted with caution given the exploratory nature of our study. Nonetheless, the overall positive benefits of IMT on the respiratory muscles support its potential clinical utility in CCS. CLINICAL TRIAL REGISTRATION: http://ClinicalTrials.gov NCT06205251 and NCT06230692.