Abstract & Commentary
The Success of Cystic Fibrosis Treatment: A New Patient Population for Hospitalists
By Deborah J. DeWaay, MD, FACP
Assistant Professor, Medical University of South Carolina, Charleston, SC
Dr. DeWaay reports no financial relationships in this field of study
SYNOPSIS: Patients born with cystic fibrosis in the current age will live to be adults and will require healthcare in the adult system.
SOURCE: MacKenzie T, Gifford A, Sabadosa K, Hebe Q, Knapp E, Goss C, Marshall B. Longevity of Patients With Cystic Fibrosis in 2000 to 2010 and Beyond: Survival Analysis of the Cystic Fibrosis Foundation Patient Registry. Ann Intern Med. 161(4):233-241. August 2014
Patients with cystic fibrosis (CF) have a dysfunctional CF transmembrane conductance regulator (CFTR) epithelial chloride channel. As a result, the channel prevents their secretions from being adequately hydrated. In addition to causing pancreatic dysfunction, malabsorption and infertility, this genetically recessive disease shortens a patient’s life span because the inadequate clearance of secretions from the lungs leads to bronchiectasis and chronic infections. The Cystic Fibrosis Foundation Patient Registry (CFFPR) tracks patients with this disease in an attempt to describe the natural history of the illness. In 2010, 26,000 of the 30,000 people living with CF in the United States were registered in the CFFPR.
There are 260 programs for CF patients that are included in 110 Cystic Fibrosis Foundation accredited care centers that participate in the CFFPR. Patient data (age of diagnosis, clinical presentation, respiratory cultures, pulmonary function tests, nutritional status, therapies and complications) are collected via a Web-based portal system. This study analyzed data from Jan. 1, 2000, through Dec. 31, 2010. Multivariable Cox proportional hazard models were used to analyze mortality trends in the data. In order to account for patient characteristics that are not modifiable, the authors made adjustments for race, gender, presence of symptoms at diagnosis, F508del mutation status, and age at diagnosis. The authors made the assumption that most diagnoses would be made using the newborn screen and that diagnoses made later in life would be patients with a milder phenotype who had residual CFTR function.
The median age of the cohort increased from 14.3 years in 2000 to 16.7 years in 2010. In addition, patients who were 18 years and older reached an all-time high of 48%.
The authors analyzed the data to estimate mortality trends in 3 different ways. First, if the mortality rate were to indefinitely stay at 2010 levels the median survival for children born in 2010 with CF will be 39 years (CI, 38-40 years). Second, if the mortality rate were to decrease indefinitely at the rate calculated between 2000 and 2010, 1.8%, the median survival for children born in 2010 with CF will be 56 years (CI, 54-58 years). Third, if the mortality rate were to decrease at one-half the rate calculated between 2000 and 2010, 0.9%, the median survival will be 45 years old (CI, 44-46 years).
COMMENTARY
It won’t be long before more than half of patients with cystic fibrosis are over the age of 18. Based on this study, the median life expectancy of children born with CF in 2010 will be between 39 and 56 years. These patients are living longer and requiring adult care more frequently. In fact, more than half of their life will be spent as an adult. Whether patients with CF are receiving their care at an academic medical center, or at a non-academic center, hospitalists will be caring for more patients with CF in the future. It is important for hospitalists to be aware of this epidemiologic shift.
These increases in life expectancy are attributed to aggressive nutritional therapies including high fat and high calorie diets, daily regimens of airway clearance, antibiotics, new inhaled medications to break up mucus, aggressive diabetes management and universal newborn screening. Yet as patients with CF live longer, they are developing complications from their therapies as well as their disease. Aminoglycosides, for example, that are frequently used to treat CF exacerbations, lead to kidney and vestibular injury. CF diabetes leads to the complications typical of diabetes: retinopathy, neuropathy and nephropathy. Patients will be more likely to develop colon cancer, chronic renal insufficiency, and hypertriglyceridemia. Mental health concerns continue to be an issue as this population ages and depression occurs in roughly 30% of patients with CF. These are all issues with which hospitalists are very familiar. Hospitalists will also have a role as a part of the multidisciplinary team required to care for this patient population during an acute pulmonary exacerbation.
Limitations of this study include the following. First, 2% of patients were lost to follow up. Second, over 12% of patients in the registry were missing data. Third, these projections apply to patients who are diagnosed within the first year of life. Those diagnosed later should have a better prognosis because they are more likely to be pancreatic-sufficient. Fourth, all of these patients are receiving care at specialized medical centers that participate in the registry and thus the projected survival may be overestimated. Nevertheless, the findings of this study are consistent with similar findings found in the United Kingdom CF registry.
In conclusion, care of patients with CF has led to a remarkable improvement in survival and the prevalence of adult patients is increasing dramatically. Over time, hospitalists will be caring for these patients with CF as they are hospitalized for complications of their disease. It behooves us all to be aware of this change.
