F.E.S.: FESS effectiveness Study: a multi-centre randomised controlled trial studying the effectiveness of functional endoscopic sinus surgery (FESS) in adult patients with chronic rhinosinusitis/nasal polyps unresponsive to medical therapy.

Functional Endoscopic Sinus Surgery (FESS) is a well-accepted component of the management of chronic rhinosinusitis (CRS) with or without nasal polyps (NP). Evidence level III studies show success rates of FESS between 85-95% improvement. Eventhough FESS is often performed, 10.000/year in the Netherlands, evidence level I is lacking. The relevance of CRS/NP follows the high prevalence and the high impact on quality of life, which results in significant costs.

In a prospective, multi centre, randomised controlled trial the efficacy and cost-effectiveness of Functional Endoscopic Sinus Surgery (FESS) plus medical treatment is studied and compared to ongoing medical treatment. Patients having the common condition chronic rhinosinusitis with or without nasal polyps with its severe impact on the quality of life are eligible if they are refractory to the regular medical treatment and have an indication for FESS.

One treatment arm will receive FESS plus a standardised form of medical treatment. The control group will receive standardised medical treatment. The primary outcome measures is a validated rhinosinusitis specific quality of life questionnaire: Sinonasal Outcome test (4). A sample size of 77 in each group (154 in total) will have 80% power to detect a difference in means of 0.5 assuming that the common standard deviation is 1.1 using a two group t-test with a 0.05 two-sided significance level (4). The treatment arms will be stopped and evaluated at the time-point of 3 months. For the long-term follow-up evaluation of FESS the total duration of this study will be 1 year.

After checking the assumptions of normality and constant variance an unpaired t-test will be performed to compare the means in the 2 groups. The economic evaluation of FESS is designed as a cost-effectiveness study, with primary economic outcome expressed as cost difference per CRS-severity-adjusted life time. Costs are distinguished in direct medical and non-medical costs, and indirect costs; they will be estimated according to current methodology and national guidelines (12). Days of sick leave and the EuroQoL questionnaires (generic health) will be used.

The trial start-up will take a half year, inclusion-period 1 year, trial duration 1 year and analysing the results another half year, which leads to a total planned study duration of 3 years.

FESS is effective: giving significant reduction of symptoms.

The indication for FESS must be based on the symptoms of the patient and its duration, CT scan abnormalities and/or nasal endoscopic abnormalities, and a history of adequate conservative treatment.

The intervention to be investigated is FESS: Functional Endoscopic Sinus Surgery. One treatment arm will receive FESS plus a standardised form of medical treatment. The control group will receive standardised medical treatment. The standardised medical treatment is topical steroids for mild CRS (without NP). in moderate/severe disease a long-term antibiotic is added. The therapy for NP will be corticosteroids. For mild NP a spray, for moderate disease: spray and drops, and for severe disease: oral steroids with drops. Specific details are in the protocol.