The goal of this observational study is to learn more about the real-world efficacy of biologics in patients with chronic rhinosinusitis with nasal polyposis (CRSwNP). All patients who are 18 years or older, who have CRSwNP and are eligible for reimbursement of a biological for the indication of CRSwNP can be included.

The main question is the efficacy of biologics in real life after 24 weeks. The main focus are patient reported outcomes measured via several questionnaires and the nasal polyp score, scored with nasal endoscopy.

Chronic rhinosinusitis with nasal polyps (CRSwNP) has a prevalence of 5-10% in adults. It is often associated with other comorbidities, such as asthma (30-70% of CRSwNP patients) and aspirin exacerbated respiratory disease (AERD) (16% of CRSwNP patients) leading to a significant reduced quality of life (QoL). CRSwNP is diagnosed in patients with nasal polyps who have 2 or more of the following symptoms for more than 12 weeks:

• Nasal blockage or nasal congestion
• Runny nose or postnasal drip
• Impaired sense of smell
• Facial pain/pressure. Nasal rinses, intranasal or systemic corticosteroids, long-term antibiotics, and sinus surgery are the current standard of care. However, many patients fail to achieve complete therapeutic benefit and relapse after time, even after surgery. Moreover, oral corticosteroids are associated with significant side effects, and repeated sino-nasal surgery becomes progressively more complex with higher risk of complications. Patients with CRSwNP and most patients with asthma share a common type 2 inflammatory response, characterised by elevated levels of interleukin (IL)-4, IL-5, IL-13, eosinophils, T helper 2 (Th2)cells, and type 2 innate lymphoid cells. In addition, locally produced immunoglobulin E (IgE) is able to activate mast cells and induce local inflammation in CRSwNP.

Biologicals are a specific kind of treatment with recombinant DNA-derived humanized monoclonal antibody that selectively binds specific targets in the inflammatory cascade which contributes to the pathophysiology of CRSwNP. Different biologicals have already been reimbursement for the treatment of Asthma for years, slowly these biologicals start to get their approval and reimbursement for CRSwNP. In Belgium (omalizumab (Xolair®), mepolizumab (Nucala®) and dupilumab (Dupixent ®) are reimbursed for patients with CRSwNP. Their efficacy has been demonstrated through large double-blind placebo-controlled clinical studies. However, until now only very limited reports on real-world data regarding this therapy have been published. This real-world data is important because it enables us to go beyond data gathered throughout a traditional randomised controlled trial (RCT). Traditional RCTs gather data from a controlled sample population with limited comorbidities and concomitant medications, who are likely to be compliant with the study requirements, whereas in real life patients might have poorer performance status and compliance and consist of a higher proportion of elderly patients.

Therefore, this real-world data study aims to investigate how clinical outcomes of biologic therapy in real-world application (real-world efficacy) corresponds to outcomes in clinical trials (efficacy) and to look into factors that might explain an efficacy gap.

Inclusion Criteria:

1. Participant must be at least 18 years of age at the time of signing the informed consent.
2. Capable of giving signed informed consent.
3. Participants should have CRSwNP.
4. Participants should fulfil the reimbursement criteria for their prescribed biological (omalizumab, mepolizumab and/or dupilumab).

Exclusion Criteria:

1. Patients treated with other biological therapies in the 3 months prior to the current biological (this is not applicable to patients who are in the trial and switch biological).

Patients with CRSwNP that are prescribed a biological in the outpatient clinic of several ENT departments across Belgium