Clinical use of tobramycin inhalation solution (TOBI®) shows sustained improvement in FEV₁ in cystic fibrosis

Objectives Tobramycin inhalation solution (TIS; TOBI®) has improved forced expiratory volume in 1 sec (FEV₁) in cystic fibrosis (CF) trials. Using data from the Epidemiologic Study of CF (ESCF), we assessed the change in level and trend of FEV₁ % predicted (pred) over a 2-year period associated with initiation of TIS during routine clinical practice. Methods Patients age 8-38 years and in ESCF for ≥2 years before treatment with TIS as a chronic therapy were selected if they remained on therapy for 2 years, defined as being on TIS for at least 3 months per year (C-TIS group). Comparator intervals age 8-38 years used TIS <10% of the time. For each interval, we estimated the level and trend (rate of decline) in FEV₁ % pred before and after the index using a piecewise linear mixed-effects model adjusted for potential confounders. Results During the 2-year pre-index period the C-TIS group (n = 2,534) had a more rapid decline in FEV₁ (-2.49% vs. -1.39% pred/year) and a lower FEV₁ at index (62.6% vs. 74.7% pred) than the comparator group (N = 17,656 intervals). After starting chronic TIS, the FEV₁ trend line over the 2-year post-index period was higher, but the comparator group's FEV₁ was essentially unchanged (difference 2.22, P < 0.001). Change in slope was not different between groups (0.06, P = 0.82). Conclusions Initiating chronic TIS therapy in the routine clinical care of patients with CF was associated with improvement in FEV₁ % pred but no change in rate of decline, which means that this benefit was sustained over the 2 years studied.