Longitudinal assessment of lung function in Swiss childhood cancer survivors

RationaleChildhood cancer survivors (CCSs) are at increased risk for pulmonary morbidity due to exposure to lung-toxic treatments, including specific chemotherapies, radiotherapy, and surgery. Longitudinal data on lung function, with information on how outcomes change over time, in CCSs are scarce. ObjectivesTo investigate lung function trajectories in childhood cancer survivors over time and investigate the association with lung-toxic treatment. MethodsThis retrospective, multi-center cohort study included CCSs, who were diagnosed between 1990 and 2013 in Switzerland and had been exposed to lung-toxic chemotherapeutics or thoracic radiotherapy. Pulmonary function tests (PFTs) were obtained from hospital charts. We assessed quality of PFTs systematically and calculated z-scores and percentage predicted of forced expiratory volume in first second (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, total lung capacity (TLC) and diffusion capacity for carbon-monoxide (DLCO) based on recommended reference equations. We described lung function over time and determined risk factors for change in FEV1 and FVC using multivariable linear regression. ResultsWe included 790 PFTs from 183 CCSs, with a median age of 12 years (IQR 7 - 14) at diagnosis. Common diagnoses were lymphoma (55%), leukemia (11%) and CNS tumors (12%). Median follow-up time was 5.5 years. Half (49%) of CCSs had at least one abnormal pulmonary function parameter, with restrictive impairment being common (22%). Trajectories of FEV1 and FVC started at z-scores of -1.5 at diagnosis and remained low throughout follow-up. CCSs treated with thoracic surgery started particularly low, with an FEV1 of -1.08 z-scores (-2.02 to -0.15) and an FVC of -1.42 z-scores (-2.27 to -0.57) compared to those without surgery. In CCS exposed to lung-toxic chemotherapeutics FEV1 z-scores increased slightly over time (0.12 per year; 95%CI 0.02 - 0.21). ConclusionThe large proportion of CCSs with reduced lung function identified in this study underlines the need for more research and long-term surveillance of this vulnerable population.