Impact of CFTR modulator therapy on body composition as assessed by thoracic computed tomography: A follow-up study

Treatment with cystic fibrosis transmembrane conductance regulator (CFTR) modulators in individuals with cystic fibrosis (CF) has brought a significant change in forced expiratory volume in 1 second (FEV₁) and clinical parameters. However, it also results in weight gain. The aim of our study is to evaluate the effect of CFTR modulator treatment on body composition, measured by computed tomography (CT).

Adult subjects with CF under follow-up at La Princesa University Hospital were recruited. All of them were on elexacaftor-tezacaftor-ivacaftor (ELX/TEZ/IVA) treatment. Body composition analysis was conducted using CT scans and an open-source software. The results were then compared with bioimpedance estimations, as well as other clinical and spirometry data.

Our sample consisted of 26 adult subjects. The fat mass compartments on CT scans correlated with similar compartments on bioimpedance, and normal-density muscle mass exhibited a strong correlation with phase angle. Higher levels of very low-density muscle prior to treatment were associated with lower final FEV₁ and less improvement in FEV₁ after therapy. We observed an increase in total body area (P < 0.001), driven by increases in total fat mass (P < 0.001), subcutaneous fat (P < 0.001), visceral fat (P = 0.002), and intermuscular fat (P = 0.022). The only muscle compartment that showed an increase after treatment was very low-density muscle (P = 0.032).

CT scans represent an opportunity to assess body composition on CF. Combination treatment with CFTR modulators, leads to an improvement in FEV₁ and to an increase in body mass in all compartments primarily at the expense of fat mass.