Data collection time points in months.

Introduction
Cystic fibrosis (CF) is commonly complicated by chronic rhinosinusitis (CRS). Despite highly effective management options, CRS in people with CF (PwCF+CRS) may be refractory to medical therapy, eventually requiring endoscopic sinus surgery. The impact of sinus surgery on pulmonary, quality of life (QOL), and other outcomes in PwCF+CRS in the expanding era of highly effective modulator therapy has not been fully elucidated. This study aims to determine if endoscopic sinus surgery can offer superior outcomes for PwCF+CRS when compared to continued medical treatment of CRS.
Methods and analysis
This multi-institutional, observational, prospective cohort study will enroll 150 adults with PwCF+CRS across nine US CF Centers who failed initial medical therapy for CRS and elected to pursue either endoscopic sinus surgery or continue medical treatment. To determine if sinus surgery outperforms continued medical therapy in different outcomes, we will assess changes in pulmonary, CF-specific QOL, CRS-specific QOL, sleep quality, depression, headache, cognition, olfaction, productivity loss, and health utility value after treatment. The influence of highly effective modulator therapy on these outcomes will also be evaluated. This study will provide crucial insights into the impact of endoscopic sinus surgery for PwCF+CRS and aid with development of future treatment pathways and guidelines.
Ethics and dissemination
This study has been approved by each institution’s internal review board, and study enrollment began August 2019. Results will be disseminated in conferences and peer-reviewed journals.
Trial registration
This study was registered on ClinicalTrials.gov (NCT04469439).