Treatment with ivacaftor is associated with a change from pancreatic exocrine insufficiency (PI) to pancreatic sufficiency (PS) in children with cystic fibrosis and gating mutations, Australian research shows.

In a WA study of 204 children and adolescents with CF, all 12 patients eligible for ivacaftor were pancreatic insufficient (PI) at diagnosis and 11 were on pancreatic enzymes replacement therapy (PERT).

The study, published as a letter in Pediatric Pulmonology, found 36% (4/11 patients) became PS after starting ivacaftor.

“Children are more likely to change function if initial pancreatic elastase is more than 50 μg/g and if ivacaftor is started at a younger age,” it said.

“Potentially children eligible for ivacaftor at 1 year of age with borderline pancreatic function can now be managed without PERT if growing well.”

The study said that two of the four children on ivacaftor experienced recurrent abdominal pain while taking PERT. Their symptoms resolved when PERT was discontinued.

Another child with a residual CFTR function mutation became constipated before repeat testing of pancreatic function.

“There are many causes of abdominal pain and constipation in CF, and change in pancreatic status should be considered,” the researchers said.

The study also found that in 35 patients with at least one residual CFTR function mutation, most (83%) had pancreatic elastase above 200 μg/g since diagnosis.

Two had spontaneously become PS before the age of 2 years and the remaining three were offered retesting. Two became PS at ages 3 and 16 years; only one patient with a residual CFTR function mutation continues to be PI.

“Most changed to PS before age 4 years and if their initial pancreatic elastase was over 150 μg/g.”

Dr Rachael Marpole and Dr Andrew Wilson, from the Department of Respiratory and Sleep Medicine at Perth Children’s Hospital, said there was benefit in reviewing pancreatic function regularly in patients on CF modulators.

“This review is especially important for patients on ivacaftor for a gating mutation or elexacaftor−tezacaftor−ivacaftor, have residual CFTR function mutations or have new abdominal pain when taking PERT.”

“Regular reassessment of pancreatic function will prevent inappropriate PERT prescription and reduce side effects.”

They said Nutrition Guidelines for CF in Australia and New Zealand suggest all children with CF have pancreatic function tested at diagnosis with repeat testing to guide PERT in patients on CF modulators.