Trends in the clinical characteristics of the U.S. cystic fibrosis patient population from 1995 to 2005

Epidemiologic Study of Cystic Fibrosis: 25 years of observational research

The Epidemiologic Study of Cystic Fibrosis (ESCF) was a prospective observational study of over 32,000 people with cystic fibrosis (CF) from 250 clinical care sites in North America from 1994 to 2005. Begun as a pharmacovigilance study in connection with the approval of dornase alfa in 1993, ESCF was open to all people with CF treated at any participating site in the United States or Canada. In addition to obtaining safety and effectiveness data on dornase alfa, ESCF collected encounter-based data to characterize the natural history and management of CF with a special focus on lung disease. During the study, 32,178 patients reported at least one encounter, contributing 869,136 encounters, 622,592 pulmonary function tests, 432,896 cultures, and 118,563 pulmonary exacerbations treated with intravenous antibiotics. Although ESCF data collection concluded in 2005, through a collaboration with the U.S. Cystic Fibrosis Foundation Patient Registry, additional follow-up data through 2017 was available for two-thirds of patients. This allowed for updating of CF genotype and survival information. Fifty-six peer-reviewed publications (cited over 3600 times) resulted from this study. In this manuscript we summarize the published ESCF manuscripts in thematic groups with key study findings and brief comments, and speculate on how ESCF findings will inform future data registries and patient care practices.

Use of ibuprofen to assess inflammatory biomarkers in induced sputum: Implications for clinical trials in cystic fibrosis

BACKGROUND

High-dose ibuprofen (HDI) is a clinically beneficial anti-inflammatory regimen that may be a useful reagent to study induced sputum inflammatory marker changes over short study periods appropriate for early-phase CF clinical trials.

METHODS

We conducted a 28-day, open-label, randomized, controlled trial among 72 clinically stable CF subjects (FEV1≥40% predicted) randomized to HDI or routine care that assessed IL-6, IL-8, TNF-α, IL-1-β, free neutrophil elastase, and white cell counts with differentials change from baseline in induced sputum.

RESULTS

IL-6 was the only biomarker with significant within-group change: 0.13 log10 pg/mL mean reduction among ibuprofen-treated subjects (p=0.04); and no change in the control group. IL-6 change between groups was statistically significant (p=0.024). No other inflammatory biomarker differences were observed between groups after 28 days.

CONCLUSION

Although we studied only one agent, HDI, these results suggest that one month may be inadequate to assess anti-inflammatory candidates using markers from induced sputum.

Utilization of patient-reported outcomes as a step towards collaborative medicine

Patient-reported outcomes (PROs) have been successfully developed for a variety of chronic respiratory diseases, such as asthma and cystic fibrosis (CF). They have recently been used to evaluate the efficacy of new medications and assess current patient functioning. Although regulatory bodies have favored PROs that measures symptoms, other domains of functioning, such as treatment burden, should be considered. This review examines current guidelines for the development and application of PROs in clinical trials, describes methods for selecting appropriate measures for paediatric populations, and presents a model incorporating PROs into clinical practice. Guidance on interpretation of these measures and graphic presentation of results are illustrated. PROs can serve as the link between the health care provider and patient to foster collaborative and personalized medicine. This model promotes greater patient responsibility, facilitates communication with providers, encourages shared decision-making, and enhances adherence.

Risk factors for onset of persistent respiratory symptoms in children with cystic fibrosis

OBJECTIVES

To characterize the onset of persistent signs and symptoms of cystic fibrosis (CF) lung disease and identify characteristics that predict onset.

STUDY DESIGN

Patients in the Epidemiologic Study of CF who were <4 years of age at enrollment and had ≥2 years of follow-up were included. We defined persistence as a sign or symptom that was present during two consecutive encounters separated by 60-365 days, and persistent clubbing as ≥50% of encounters with clubbing within 365 days. Predictors were assessed in a Cox proportional hazards model for age at first occurrence of each symptom.

RESULTS

Each sign or symptom met the criterion of persistence in a substantial proportion of patients during a follow-up period of 7 ± 3 years (mean ± SD; range 2-12). Risk factors that predicted earlier onset of signs and symptoms included pancreatic enzyme use, Pseudomonas aeruginosa infection, and prior diagnosis of asthma. Other risk factors had variable effects on signs and symptoms.

CONCLUSIONS

Signs and symptoms of lung disease begin early in CF. Risk factors previously reported for lower forced expiratory volume in 1 sec are also associated with earlier onset of persistent signs and symptoms of CF lung disease, but their impact varies.

An overview of international literature from cystic fibrosis registries. Part 4: update 2011

A total of 53 national cystic fibrosis (CF) patient registry studies published between July 2008 and November 2011 have been reviewed, focusing on the following topics: CF epidemiology, nutrition, microbiology, clinical complications, factors influencing diagnosis and lung disease, effects of socioeconomic status, therapeutic strategy evaluation, clinical trial methodology. The studies describe the clinical characteristics of CF patients, the incidence and prevalence of disease and role of gender gap, as well as the influence of socioeconomic status and environmental factors on clinical outcomes, covering a variety of countries and ethnic groups. Original observations describe patients as they get older, with special reference to the adult presentation of CF and long-term survival. Methodological aspects are discussed, covering the design of clinical trials, survival analysis, auxometry, measures of quality of life, follow up of lung disease, predictability of disease progression and life expectancy. Microbiology studies have investigated the role of selected pathogens, such as Burkholderia species and MRSA. Pulmonary exacerbations are discussed both as a factor influencing morbidity and an endpoint in clinical trials. Finally, some studies give insights on complications, such as CF-related diabetes and hemoptysis, and emerging problems, such as chronic nephropathy.

Outcome measures for clinical trials assessing treatment of cystic fibrosis lung disease

Cystic fibrosis (CF) is a complex genetic disease characterized by death from loss of lung function. Therapies target pathophysiologic changes associated with pulmonary disease progression. Although therapeutic mechanisms differ, efficacy demonstration is limited to a few accepted outcome measures, each with shortcomings that are becoming more pronounced as CF population health improves. Pulmonary function improvement (as forced expiratory volume in 1 s [FEV₁]) and reduction of pulmonary exacerbation risk are commonly used outcomes. Changes in FEV₁ decline rate, quality of life, linear growth and/or weight gain are less utilized outcomes. Validated outcomes tend to work best in subjects with more aggressive or advanced lung disease and less so in healthier subjects. Assays of effects on primary therapeutic targets have yet to be validated as surrogate measures of clinical efficacy. As CF population health improves, it will become increasingly difficult to employ current clinical outcome measures to demonstrate efficacy.

Design and powering of cystic fibrosis clinical trials using pulmonary exacerbation as an efficacy endpoint

BACKGROUND

Reduction in pulmonary exacerbations is an important efficacy endpoint for CF clinical studies. Powering exacerbation endpoints requires estimation of the future exacerbation incidence in CF study populations, but rates differ across the population.

METHODS

We have estimated exacerbation rates for Epidemiologic Study of CF subpopulations stratified by age, FEV(1)% predicted, sex, weight-for-age percentile, respiratory signs and symptoms, and history of exacerbation and bacterial culture. Sample sizes required to attain 80% power to detect exacerbation reductions of 20% to 80% in 1:1 randomized studies of 3 to 12 month duration were determined. Exacerbation treatments with "any" antibiotic (new oral quinolone, new inhaled antibiotic, or intravenous (IV) antibiotic) and with IV antibiotics were studied.

RESULTS

At all ages, decreased FEV(1), female sex, exacerbation history, and Pseudomonas aeruginosa culture history were associated with increased treatment for exacerbation.

CONCLUSIONS

These data should assist investigators in the design of future CF exacerbation studies.

Levofloxacin inhalation solution (MP-376) in patients with cystic fibrosis with Pseudomonas aeruginosa

RATIONALE

Lower respiratory tract infection with Pseudomonas aeruginosa (PA) is associated with increased morbidity in patients with cystic fibrosis (CF). Current treatment guidelines for inhaled antibiotics are not universally followed due to the perception of decreased efficacy, increasing resistance, drug intolerance, and high treatment burden with current aerosol antibiotics. New treatment options for CF pulmonary infections are needed.

OBJECTIVES

This study assessed the efficacy and safety of a novel aerosol formulation of levofloxacin (MP-376, Aeroquin) in a heavily treated CF population with PA infection.

METHODS

This study randomized 151 patients with CF with chronic PA infection to one of three doses of MP-376 (120 mg every day, 240 mg every day, 240 mg twice a day) or placebo for 28 days. The primary efficacy endpoint was the change in sputum PA density. Secondary endpoints included changes in pulmonary function, the need for other anti-PA antimicrobials, changes in patient-reported symptom scores, and safety monitoring.

MEASUREMENTS AND MAIN RESULTS

All doses of MP-376 resulted in reduced sputum PA density at Day 28, with MP-376 240 mg twice a day showing a 0.96 log difference compared with placebo (P = 0.001). There was a dose-dependent increase in FEV(1) for MP-376, with a difference of 8.7% in FEV(1) between the 240 mg twice a day group and placebo (P = 0.003). Significant reductions (61-79%) in the need for other anti-PA antimicrobials were observed with all MP-376 treatment groups compared with placebo. MP-376 was generally well tolerated relative to placebo.

CONCLUSIONS

Nebulized MP-376was well tolerated and demonstrated significant clinical efficacy in heavily treated patients with CF with PA lung infection. Clinical trial registered with www.clinicaltrials.gov (NCT00677365).

Pulmonary outcome prediction (POP) tools for cystic fibrosis patients

RATIONALE

Loss of lung function in patients with cystic fibrosis (CF) is associated with increased mortality and varies between individuals and over time. Predicting this decline could improve patient management.

OBJECTIVES

To develop simple pulmonary outcome prediction (POP) tools to estimate lung function at age 6 in patients aged 2-5 years (POP(2-5)) and lung function change over a 4-year period in patients aged 6-17 years (POP(6-17)).

METHODS

Analyses were conducted using patients from the Epidemiologic Study of CF (ESCF). To be included in any analysis, patients had to have 1 year of clinical history recorded in ESCF prior to a clinically stable routine Index Clinic Visit (ICV). In addition to this criterion, for the POP(2-5) tool patients had to be between 2 and 5 years old at ICV and have a second clinically stable visit with spirometric measures at age 6. For the POP(6-17) tool, patients had to be between the ages of 6 and 17 years old at an ICV that included spirometric measures and had to have a second clinically stable visit with spirometric measures from 3 to 5 years after ICV. All patients enrolled in ESCF who met these inclusion criteria were studied. POP(2-5) and POP(6-17) populations were further divided into development groups (with ICV before January 1, 1998) and validation groups (with ICV after that date). Development groups were used to model forced expiratory volume in 1 sec (FEV(1)) percent predicted at age 6 years (for POP(2-5)) and annualized FEV(1) % predicted change from ICV to the second visit (for POP(6-17)) by multivariable linear regression using age, sex, weight-for-age percentile, cough, sputum production, clubbing, crackles, wheeze, sinusitis, number of exacerbations requiring intravenous antibiotics in the past year, elevated liver enzymes, pancreatic enzyme use, and respiratory tract culture status, plus height-for-age percentile (POP(2-5)) and index FEV(1) (POP(6-17)). Integer-based POP(2-5) and POP(6-17) tools created from selected variables were evaluated by Pearson correlation and then prospectively validated with separate data collected later from ESCF patients with ICV after January 1, 1998.

MAIN RESULTS

POP(2-5) and POP(6-17) development groups included 2,709 and 6,113 patients and validation groups included 3,458 and 7,086 patients, respectively. Variables retained were weight-for-age percentile, clubbing, crackles, wheeze, number of exacerbations, and Pseudomonas aeruginosa culture status (both tools), daily cough (POP(2-5)), and age, sex, and index FEV(1) % predicted (POP(6-17)). Correlation coefficients for POP(2-5) and POP(6-17) tools prospectively applied to validation groups were +0.32 and +0.37, respectively.

CONCLUSIONS

These simple integer-based POP algorithms employ variables available at clinic visits and can be used to predict the probability of different future pulmonary outcomes for individual patients and patient populations.

Trends in the use of routine therapies in cystic fibrosis: 1995-2005

Many therapies are used to treat manifestations of cystic fibrosis (CF). Trends in routine therapy use in Epidemiologic Study of Cystic Fibrosis patients were studied from 1995 to 2005. Patients (15,087) were assessed in 1995; 12,778 in 2005. Observed differences in therapy use of ≥2% were statistically significant at P < 0.001. Comparing the 1995 and 2005 populations, mean age was 13.9 versus 15.5 years; weight-for-age percentile was 30.3 versus 36.9; and mean forced expiratory volume in 1 sec (FEV(1)) was 73.7% (n = 7065) versus 78.7% (n = 7867) predicted. Use of several therapies increased, including airway clearance (69.9-89.6%), inhaled bronchodilators (72.0-84.0%), dornase alfa (44.8-67.2%), inhaled corticosteroids (16.0-49.3%), inhaled antibiotics (6.5-43.1%), oral nutritional supplements (18.3-24.5%), and insulin/oral hypoglycemic agents (4.9-10.2%). Use of mast cell stabilizers (from 22.0% to 5.3%) and oral bronchodilators (from 10.4% to 1.5%) decreased. Less dramatic changes occurred for pancreatic enzymes (92.6-91.0%), oral nonquinolone antibiotics (44.7-39.8%), oral corticosteroids (7.8-5.2%), mucolytics (4.4-2.5%), NSAIDs/high-dose ibuprofen (3.6-3.3%), enteral nutrition (5.2% vs. 8.2%), and oxygen (4.7-4.5%). Therapies not tracked in 1995 were evident in 2005, including oral macrolide antibiotics (33.8%), leukotriene inhibitors/antagonists (10.8%), and inhaled hypertonic saline (2.6%). Routine therapies were generally used more often by older patients and those with lower FEV(1). Notable increases in use of therapies, particularly of inhaled therapies, suggest that overall patient treatment burden must have risen correspondingly.