Progressive destruction of the lungs is the main cause of shortened life expectancy in people with cystic fibrosis (pwCF). Inflammation and respiratory infections play a key role in CF lung disease. Previous studies have shown that an increase in inflammatory markers predicts structural lung damage. Close monitoring of pwCF is crucial to adequately provide optimal care. Pulmonary management for pwCF involves treating infections and exacerbations and promoting exercise and mucociliary clearance to slow or prevent structural lung damage. To evaluate the treatment and incite timely interventions it is important for the pulmonary physician to be well-informed about the condition of the lungs.

The main monitoring tools in regular CF care are lung function, sputum cultures, symptom reporting and more recently imaging by chest computed tomography (CT-scan) or magnetic resonance imaging (MRI). Strangely enough, there are currently no monitoring tools used in clinics to measure inflammation in the lung, although this is a main factor for progressive lung disease.

New highly effective modulator therapy (HEMT) such as elexacaftor/tezacaftor/ivacaftor [ETI, Kaftrio®] is transforming CF treatment, vastly improving lung function and reducing exacerbations. Initial CFTR modulators like ivacaftor and lumacaftor/ivacaftor also improved lung function and reduced exacerbations, but studies showed that lung inflammation was still present. The long-term impact of ETI and its effect on inflammation is not yet known.

Thus, monitoring pwCF on HEMT may be different from before, as lung damage seen on chest CT will be less apparent and lung function will improve considerably, therefore not being adequate markers for subtle changes in the lungs. Thus, the focus of monitoring in the era of highly effective CFTR modulators needs to change preferably focusing on measuring lung inflammation.

An ideal monitoring tool for lung inflammation in pwCF should be non-invasive, efficient, and provide accurate and sensitive results. Currently, sputum and BAL are the most common methods for assessing inflammation, but BAL is invasive and sputum may not always be available. Exhaled breath analysis by the electronic nose (eNose) or gas chromatography-mass spectrometry (GC-MS) of volatile organic compounds (VOCs) shows promise as a non-invasive monitoring tool. Other promising markers and techniques are inflammatory markers in the blood (cytokines and micro-RNA (miRNA)) and urine.

Thus, the objective of this project is to design novel, minimally invasive monitoring techniques capable of identifying lung inflammation in pwCF undergoing highly effective CFTR modulator therapy (ETI) compared to those not using CFTR modulators. The efficacy of these innovative techniques will be evaluated and verified against inflammatory markers in sputum, spirometry, and validated symptom and quality of life scores.

Objective:

The overall aim of the study is to develop innovative minimally invasive monitoring techniques that can identify lung inflammation in pwCF when using highly effective modulators, compared to patients whom are not eligible for CFTR modulators (control group) yet.

Primary objective is to assess whether measuring VOCs with GC-MS is a sensitive method to monitor changes in lung inflammation in pwCF.

Secondary objectives are:

• To assess whether eNose is a sensitive method to monitor changes in lung inflammation in pwCF.
• To explore the usefulness of other inflammatory markers in blood and urine.

Study design: Explorative cohort study aimed to develop innovative minimally invasive monitoring techniques that can identify lung inflammation in pwCF when using highly effective CFTR modulators. (eNose, GC-MS, inflammatory markers in urine and blood), compared to a control group: pwCF not using CFTR modulators. Furthermore, the investigators will compare these techniques with inflammatory markers in induced sputum, conventional spirometry, symptom and quality of life scores.

Study population: pwCF older than 6 years of age who are eligible to start on ETI treatment and as a control group pwCF who are not on CFTR modulators,

Intervention: Subjects will be included till at least 3 study visits have taken place during treatment with ETI or for the control group: 3 consecutive regular outpatient clinic visits, which are usually 3 months apart. If the subject has not started with ETI an extra visit at baseline will be added just before start of ETI. At the study visits routine care checks will be done, such as spirometry and blood sampling for liver enzyme monitoring. The extra investigations performed at these study visits are: exhaled breath sampling, 3 extra vials of blood, urine collection, induced sputum. Lung clearance index (LCI) will be done for subjects below 18 years of age. Subjects may opt out for blood, induced sputum and urine samples, there always need to be an exhaled breath sampling with eNose and GC-MS. If the patient has a contra-indication or does not want to participate in the induced sputum procedure, the investigators will attempt to collect spontaneous expectorated sputum instead.

To limit their burden of the study for the age group 6-11, the investigators will not conduct all measurements in that age group. Resulting, in the following difference in study design between two age groups:

Patients >12 years: At all visits there will be exhaled breath sampling, 3 extra vials of blood with a blooddraw, induced sputum, urine sample and 2 questionnaires (QoL and symptom score).

Patients <12 years: At all visits there will be exhaled breath sampling and 1 questionnaire (symptom score) will be done by doing an interview with the child. On the last visit 2 extra vials of blood will be collected. For patients 6-18 years of age a multiple breath washout (MBW) for LCI will be scheduled at study visits.

Main study parameters/endpoints:

Primary endpoint is the comparison of VOCs, measured by GC-MS, during ETI treatment compared to control group over time during 3 different study visits.

Secondary endpoints entail the correlation of VOCs by GC-MS breath profiles/VOCs, measured by eNose, inflammatory markers in induced sputum (IL-8, free neutrophilic elastase (NE), calprotectin and myeloperoxidase, plus a predetermined cytokine panel), blood (IL-18, IL-1β, TNF, hsCRP, sCD14, calprotectin, HGMB-1, amyloid and miRNA), urine and, lung function, quality of life and symptom scores at baseline (if available) and overtime during 3 consecutive study visits. In addition, the change of VOCs by GC-MS and eNose from baseline till 3 months of ETI treatment will be investigated.

Inclusion Criteria:

In order to be eligible to participate in this study, a subject must meet all of the following criteria:

Diagnosed with CF, either by abnormal sweat test and/or confirmed with 2 CF causing mutations found by genetic analysis, either from heel-prick screening or diagnosed later in life. Aged >6 years (i.e. children and adults). Age appropriate written informed consent is required.

In addition, patients need to meet the criteria of one of the following study groups:

Group 1: Treated group : people with CF with mutations who are eligible to start ETI or who are already using it. This maybe patients who transition from another CFTR modulator or who are CFTR modulator naïve.

Group 2: Control group: people with CF whom are not eligible to start on any CFTR modulator yet and receive standard treatment. This group will function as controls.

Exclusion Criteria:

- People with CF who cannot follow instructions

people with CF older than 6 years of age who are eligible to start on ETI treatment and as a control group people with CF who are not on CFTR modulators.