Cystic fibrosis: Advances, ongoing challenges
After Rena Barrow-Wells, an African American mother, fought mightily to prevent a repeat of her experience of two decades earlier when her first child’s cystic fibrosis (CF) took 4 years to diagnose, her story became the subject of a New York Times feature covering disparities in diagnostic CF screening. The article highlighted not only her struggles, but also the utter transformation of the CF landscape since the introduction of small molecule mutation-specific drugs. These drugs restore function to defective CF transmembrane conductance regulator (CFTR) proteins. By the time Ms. Barrow-Wells’ young son was treated, lung and pancreatic scarring were already significant. So when the 39-mutation variant screening test available in Ms. Barrow-Wells’ Lawrenceville, Georgia, clinic turned out negative for CF, her pediatrician told her to stop worrying despite her new son’s inherent genetic risk, telltale salty skin, foul-smelling diapers, and her pleas to test for sweat chloride. It still took 3 months for a confirmed diagnosis and the initiation of treatment.
Current genetic tests, based largely on older clinical trials that enrolled mostly white children, are highly accurate for identifying CF in white babies (95%), but often fail to identify substantial percentages of mutations originating in Africa, Asia, and Latin America. They miss CF in Asian (44%), Black (22%), and Hispanic, Native American and Alaskan Native babies (14%), the Times article stated. In the United States, the number of CF variants tested for falls into a wide range: from the one variant found mostly in White populations in Mississippi (with a 38% Black populace) to 689 variants in Wisconsin.
Not too far back, CF was thought of as an inherited childhood disease leading often to childhood or adolescent mortality.
Today’s CF challenges
Beyond refinements in screening instruments and policies that broaden access leading to the earliest possible diagnoses, ongoing research needs include finding treatments for other variants, and caring for adult populations living with treated CF and the disease’s multisystem manifestations. “As people with CF live longer, we need to be very focused on optimized adult medical care for this population,” Marc A. Sala, MD, assistant professor of medicine, Adult CF Program, Northwestern University Feinberg School of Medicine, Chicago, said in an interview. “For example, we need higher vigilance for liver, microvascular, coronary artery disease, and various cancer screenings. We do not know exactly how these will manifest differently from the way they do in non-CF populations, so this is where more work needs to be done.”
Emphasis on monitoring
The authors of “Future therapies for cystic fibrosis” (Allen et al. Nature Communications, 2023 Feb 8), after citing the ongoing transformative change for people with CF since the introduction of CFTR drugs, gave voice to important cautions. “Disease will progress, albeit more slowly, and will be more challenging to monitor. Effective CFTR modulators will likely slow or, at best, halt disease progression, but will not reverse a disease that has already become fixed.” They cited pancreatic destruction in the majority, bronchiectasis, and absence of the vas deferens, with still recurring (although less frequently) pulmonary exacerbations along with chronic infections and persistent airway inflammation. “It is essential that we do not become complacent about disease progression in this population,” the researchers stated. They cautioned also that effective surveillance for infection is critical in asymptomatic patients, emphasizing that it underpins the management of young healthy children with CF who demonstrate disease progression despite a lack of symptoms.
Among the ~90% for whom Trikafta is suitable and approved (those with least one copy of F508del or specific other responsive mutations), improvements include increased percent predicted FEV1 by 10%-15% or more, decreased exacerbations, and improved quality of life,” Dr. Sala said. “Subsequent ‘real world’ experience shows dramatic reductions in sputum production and decreased frequency of lung transplant.”
