Heterogeneity of CFTR modulator-induced sweat chloride concentrations in people with cystic fibrosis

BACKGROUND

Sweat chloride (SC) concentrations in people with cystic fibrosis (PwCF) reflect relative CF transmembrane conductance regulator (CFTR) protein function, the primary CF defect. Populations with greater SC concentrations tend to have lesser CFTR function and more severe disease courses. CFTR modulator treatment can improve CFTR function within specific CF genotypes and is commonly associated with reduced SC concentration. However, SC concentrations do not necessarily fall to concentrations seen in the unaffected population, suggesting potential for better CFTR treatment outcomes. We characterized post-modulator SC concentration variability among CHEC-SC study participants by genotype and modulator.

METHODS

PwCF receiving commercially approved modulators for ≥90 days were enrolled for a single SC measurement. Clinical data were obtained from chart review and the CF Foundation Patient Registry (CFFPR). Variability of post-modulator SC concentrations was assessed by cumulative SC concentration frequencies.

RESULTS

Post-modulator SC concentrations (n = 3787) were collected from 3131 PwCF; most (n = 1769, 47 %) were collected after elexacaftor/tezacaftor/ivacaftor (ETI) treatment. Modulator use was associated with lower SC distributions, with post-ETI concentrations the lowest on average. Most post-ETI SC concentrations were <60 mmol/L (79 %); 26 % were <30 mmol/L. Post-ETI distributions varied by genotype. All genotypes containing at least one F508del allele had individuals with post-ETI SC ≥60 mmol/L, with the largest proportion being F508del/minimal function (31 %).

CONCLUSIONS

Post-modulator SC concentration heterogeneity was observed among all genotypes and modulators, including ETI. The presence of PwCF with post-modulator SC concentrations within the CF diagnostic range suggests room for additional treatment-associated CFTR restoration in this population.

The effect of discontinuing hypertonic saline or dornase alfa on mucociliary clearance in elexacaftor/tezacaftor/ivacaftor treated people with cystic fibrosis: The SIMPLIFY-MCC Study

Many people with CF (pwCF) desire a reduction in inhaled treatment burden after initiation of elexacaftor/tezacaftor/ivacaftor. The randomized, open-label SIMPLIFY study showed that discontinuing hypertonic saline (HS) or dornase alfa (DA) was non-inferior to continuation of each treatment with respect to change in lung function over a 6-week period. In this SIMPLIFY substudy, we used gamma scintigraphy to determine whether discontinuation of either HS or DA was associated with deterioration in the rate of in vivo mucociliary clearance (MCC) in participants ≥12 years of age. While no significant differences in MCC endpoints were associated with HS discontinuation, significant improvement in whole and peripheral lung MCC was observed after discontinuing DA. These results suggest that pwCF on ETI with mild lung disease do not experience a subclinical deterioration in MCC that could later impact health outcomes after discontinuing HS, and in fact may benefit from improved MCC after stopping DA treatment.

The cost of simplifying treatments for cystic fibrosis: Implications of the SIMPLIFY trial

BACKGROUND

Dornase alfa and hypertonic saline are mucoactive therapies that can improve respiratory symptoms in people with cystic fibrosis (CF). A recent randomized control trial showed that participants with well-preserved pulmonary function taking elexacaftor + tezacaftor + ivacaftor (ETI) who discontinued dornase alfa or hypertonic saline for 6 weeks had no clinically meaningful decline in lung function. This may prompt discussions with care providers regarding ongoing use of these medications.

OBJECTIVE

To compare the costs of outpatient medications between people taking ETI who continued or discontinued (1) dornase alfa or (2) hypertonic saline from 2 clinical trials and project cost differences in the US CF population if these 2 medications were used only intermittently for symptom relief instead of chronically.

METHODS

The SIMPLIFY study was 2 parallel multicenter trials that randomized participants 1:1 to either continue or discontinue therapy. To estimate costs, we used data from the Merative MarketScan Databases to identify people with CF from 2020 to 2021. Our primary outcomes were differences in costs of outpatient prescription drugs among those who continued vs discontinued dornase alfa and, separately, hypertonic saline. We obtained adjusted differences in median costs. To estimate the annual cost savings if the population of people with CF taking ETI used these medications only intermittently, we multiplied the proportion of people in MarketScan with CF diagnoses who were taking each of these medications by the median cost savings per year and subtracted the cost of "rescue" use.

RESULTS

A total of 392 participants from the dornase alfa trial and 273 from the hypertonic saline trial were included in analyses. The adjusted difference in median medication costs was not significant for the hypertonic saline trial, but we observed a significantly decreased 6-week cost of medications in the dornase alfa trial (adjusted median difference in costs between discontinue and continue of $5,860 (95% CI = $4,870-$6,850); P < 0.0001). We estimated that two-thirds of people with CF use ETI and dornase alfa in the United States; if they discontinued dornase alfa except for intermittent use, the resulting annual savings would be $1.21 billion.

CONCLUSIONS

Although the costs of dornase alfa and hypertonic saline are smaller compared with ETI, reduction in use would lead to substantial prescription drug cost savings and reduce the treatment burden. However, individual benefits of these therapies should be considered, and decisions regarding changes in therapy remain an important discussion between people with CF and their providers. Study registration number: NCT04378153.

Standards for the care of people with cystic fibrosis; establishing and maintaining health

This is the second in a series of four papers updating the European Cystic Fibrosis Society (ECFS) standards for the care of people with CF. This paper focuses on establishing and maintaining health. The guidance is produced using an evidence-based framework and with wide stakeholder engagement, including people from the CF community. Authors provided a narrative description of their topic and statements, which were more directive. These statements were reviewed by a Delphi exercise, achieving good levels of agreement from a wide group for all statements. This guidance reinforces the importance of a multi-disciplinary CF team, but also describes developing models of care including virtual consultations. The framework for health is reinforced, including the need for a physically active lifestyle and the strict avoidance of all recreational inhalations, including e-cigarettes. Progress with cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapy is reviewed, including emerging adverse events and advice for dose reduction and interruption. This paper contains guidance that is pertinent to all people with CF regardless of age and eligibility for and access to modulator therapy.

Limited effects of azithromycin on the oropharyngeal microbiome in children with CF and early pseudomonas infection

BACKGROUND

Tobramycin inhalation solution (TIS) and chronic azithromycin (AZ) have known clinical benefits for children with CF, likely due to antimicrobial and anti-inflammatory activity. The effects of chronic AZ in combination with TIS on the airway microbiome have not been extensively investigated. Oropharyngeal swab samples were collected in the OPTIMIZE multicenter, randomized, placebo-controlled trial examining the addition of AZ to TIS in 198 children with CF and early P. aeruginosa infection. Bacterial small subunit rRNA gene community profiles were determined. The effects of TIS and AZ were assessed on oropharyngeal microbial diversity and composition to uncover whether effects on the bacterial community may be a mechanism of action related to the observed changes in clinical outcomes.

RESULTS

Substantial changes in bacterial communities (total bacterial load, diversity and relative abundance of specific taxa) were observed by week 3 of TIS treatment for both the AZ and placebo groups. On average, these shifts were due to changes in non-traditional CF taxa that were not sustained at the later study visits (weeks 13 and 26). Bacterial community measures did not differ between the AZ and placebo groups.

CONCLUSIONS

This study provides further evidence that the mechanism for AZ's effect on clinical outcomes is not due solely to action on airway microbial composition.

Understanding and addressing the needs of people with cystic fibrosis in the era of CFTR modulator therapy

Cystic fibrosis is a multiorgan disease caused by impaired function of the cystic fibrosis transmembrane conductance regulator (CFTR). Since the introduction of the CFTR modulator combination elexacaftor-tezacaftor-ivacaftor (ETI), which acts directly on mutant CFTR to enhance its activity, most people with cystic fibrosis (pwCF) have seen pronounced reductions in symptoms, and studies project marked increases in life expectancy for pwCF who are eligible for ETI. However, modulator therapy has not cured cystic fibrosis and the success of CFTR modulators has resulted in immediate questions about the new state of cystic fibrosis disease and clinical challenges in the care of pwCF. In this Series paper, we summarise key questions about cystic fibrosis disease in the era of modulator therapy, highlighting state-of-the-art research and clinical practices, knowledge gaps, new challenges faced by pwCF and the potential for future health-care challenges, and the pressing need for additional therapies to treat the underlying genetic or molecular causes of cystic fibrosis.

Advancing the pipeline of cystic fibrosis clinical trials: a new roadmap with a global trial network perspective

The growing use of modulator therapies aimed at restoring cystic fibrosis transmembrane conductance regulator (CFTR) protein function in people with cystic fibrosis has fundamentally altered clinical trial strategies needed to advance new therapeutics across an orphan disease population that is now divided by CFTR modulator eligibility. The development of a robust pipeline of nucleic acid-based therapies (NABTs)-initially directed towards the estimated 10% of the cystic fibrosis population who are genetically ineligible for, or intolerant of, CFTR modulators-is dependent on the optimisation of restricted trial participant resources across multiple development programmes, a challenge that will preclude the use of gold standard placebo-controlled trials. Advancement of a full pipeline of symptomatic therapies across the entire cystic fibrosis population will be challenged by smaller effect sizes and uncertainty regarding their clinical importance in a growing modulator-treated population with more mild and stable pulmonary disease. In this Series paper, we aim to lay the foundation for clinical trial strategy and community partnership that must deviate from established and familiar precedent to advance the future pipeline of cystic fibrosis therapeutics.

Potential implicit bias in attribution of adverse events in randomized controlled trials in cystic fibrosis

INTRODUCTION

Although work to date in cystic fibrosis (CF) has elucidated frequencies and characteristics of adverse events, the accuracy of attribution of relatedness to study drug by investigators has not been assessed. We aimed to determine whether there was an association of attribution by group allocation in CF clinical trials.

METHODS

We conducted a secondary analysis from 4 CF trials of all persons who experienced an AE. Our primary outcome was the odds of an AE related to active study drug and predictor of interest was the treatment allocation. We constructed a multivariable generalized estimating equation model allowing for repeated measures.

RESULTS

A total of 785 subjects (47.5% female, mean age 12 years) had 11,974 AEs, of which 430 were serious. AE attribution was greater with receipt of active study drug as compared to placebo but did not reach statistical significance (OR 1.38, 95% CI 0.98-1.82). Significantly associated factors included female sex (OR 0.58, 95% 0.39-0.87), age (OR 1.24, 95% CI 1.06-1.46) and baseline lung function (per 10%, OR 1.16, 95% CI 1.05-1.28).

CONCLUSION

In our large study, there was a non-significant but greater odds of AE attribution (a key element of clinical trial reporting) to active study drug based on assigned treatment to study drug or control which suggests that there is a trend in physicians to attribute blinded safety data to the active drug. Interestingly, females were less likely to have AE attribution to study drug and warrants further work in development and validation of monitoring guidelines and processes.

Willingness of people with cystic fibrosis receiving elexacaftor/tezacaftor/ivacaftor (ETI) to participate in randomized modulator and inhaled antimicrobial clinical trials

OBJECTIVE

To assess the feasibility of enrolling people with CF (pwCF) taking the CFTR modulator elexacaftor/tezacaftor/ivacaftor (ETI) in clinical trials of a new modulator.

METHODS

PwCF receiving ETI at CHEC-SC study (NCT03350828) enrollment were surveyed for interest in 2-week to 6-month placebo- (PC) and active-comparator (AC) modulator studies. Those taking inhaled antimicrobials (inhABX) were surveyed for interest in PC inhABX studies.

RESULTS

Of 1791 respondents, 75% [95% CI 73, 77] would enroll in a 2-week PC modulator study versus 51% [49, 54] for a 6-month study; 82% [81, 84] and 63% [61, 65] would enroll in 2-week and 6 month AC studies; 77% [74, 80] of 551 taking inhABX would enroll in a 2-week PC inhABX study versus 59% [55, 63] for a 6-month study. Previous clinical trial experience increased willingness.

CONCLUSIONS

Study designs will affect feasibility of future clinical trials of new modulators and inhABX in people receiving ETI.

Lung Function Decline in Cystic Fibrosis: Impact of Data Availability and Modeling Strategies on Clinical Interpretations

Rationale: Studies estimating the rate of lung function decline in cystic fibrosis have been inconsistent regarding the methods used. How the methodology used impacts the validity of the results and comparability between studies is unknown. Objectives: The Cystic Fibrosis Foundation established a work group whose tasks were to examine the impact of differing approaches to estimating the rate of decline in lung function and to provide analysis guidelines. Methods: We used a natural history cohort of 35,252 individuals with cystic fibrosis aged ⩾6 years in the Cystic Fibrosis Foundation Patient Registry (CFFPR), 2003-2016. Modeling strategies using linear and nonlinear forms of marginal and mixed-effects models, which have previously quantified the rate of forced expiratory volume in 1 second (FEV1) decline (percent predicted per year), were evaluated under clinically relevant scenarios of available lung function data. Scenarios varied by sample size (overall CFFPR, medium-sized cohort of 3,000 subjects, and small-sized cohort of 150), data collection/reporting frequency (encounter, quarterly, and annual), inclusion of FEV1 during pulmonary exacerbation, and follow-up length (<2 yr, 2-5 yr, entire duration). Results: Rate of FEV1 decline estimates (percent predicted per year) differed between linear marginal and mixed-effects models; overall cohort estimates (95% confidence interval) were 1.26 (1.24-1.29) and 1.40 (1.38-1.42), respectively. Marginal models consistently estimated less rapid lung function decline than mixed-effects models across scenarios, except for short-term follow-up (both were ∼1.4). Rate of decline estimates from nonlinear models diverged by age 30. Among mixed-effects models, nonlinear and stochastic terms fit best, except for short-term follow-up (<2 yr). Overall CFFPR analysis from a joint longitudinal-survival model implied that an increase in rate of decline of 1% predicted per year in FEV1 was associated with a 1.52-fold (52%) increase in the hazard of death/lung transplant, but the results exhibited immortal cohort bias. Conclusions: Differences were as high as 0.5% predicted per year between rate of decline estimates, but we found estimates were robust to lung function data availability scenarios, except short-term follow-up and older age ranges. Inconsistencies among previous study results may be attributable to inherent differences in study design, inclusion criteria, or covariate adjustment. Results-based decision points reported herein will support researchers in selecting a strategy to model lung function decline most reflective of nuanced, study-specific goals.

Discontinuation versus continuation of hypertonic saline or dornase alfa in modulator treated people with cystic fibrosis (SIMPLIFY): results from two parallel, multicentre, open-label, randomised, controlled, non-inferiority trials

BACKGROUND

Reducing treatment burden is a priority for people with cystic fibrosis, whose health has benefited from using new modulators that substantially increase CFTR protein function. The SIMPLIFY study aimed to assess the effects of discontinuing nebulised hypertonic saline or dornase alfa in individuals using the CFTR modulator elexacaftor plus tezacaftor plus ivacaftor (ETI).

METHODS

The SIMPLIFY study included two parallel, multicentre, open-label, randomised, controlled, non-inferiority trials at 80 participating clinics across the USA in the Cystic Fibrosis Therapeutics Development Network. We included individuals with cystic fibrosis aged 12-17 years with percent predicted FEV1 (ppFEV1) of 70% or more, or those aged 18 years or older with ppFEV1 of 60% or more, if they had been taking ETI and either (or both) mucoactive therapies (≥3% hypertonic saline or dornase alfa) for at least 90 days before screening. Participants on both hypertonic saline and dornase alfa were randomly assigned to one of the two trials, and those on a single therapy were assigned to the applicable trial. All participants were then randomly assigned 1:1 to continue or discontinue therapy for 6 weeks using permuted blocks of varying size, stratified by baseline ppFEV1 (week 0; ≥90% or <90%), single or concurrent use of hypertonic saline and dornase alfa, previous SIMPLIFY study participation (yes or no), and age (≥18 or <18 years). For participants randomly assigned to continue their therapy during a given trial, this therapy was instructed to be taken at least once daily according to each participant's pre-existing, clinically prescribed regimen. Hypertonic saline concentration was required to be at least 3%. The primary objective for each trial was to determine whether discontinuing was non-inferior to continuing, measured by the 6-week change in ppFEV1 in the per-protocol population. We established a non-inferiority margin of -3% for the difference between groups in the 6-week change in ppFEV1. Safety outcomes were analysed in the intention-to-treat population. This study is registered with ClinicalTrials.gov, NCT04378153.

FINDINGS

From Aug 25, 2020, to May 25, 2022, a total of 672 unique participants were screened for eligibility for one or both trials, resulting in 847 total random assignments across both trials with 594 unique participants. 370 participants were randomly assigned in the hypertonic saline trial and 477 in the dornase alfa trial. Participants across both trials had an average ppFEV1 of 96·9%. Discontinuing treatment was non-inferior to continuing treatment with respect to the absolute 6-week change in ppFEV1 in both the hypertonic saline trial (-0·19% [95% CI -0·85 to 0·48] in the discontinuation group [n=133] vs 0·14% [-0·51 to 0·78] in the continuation group [n=140]; between-group difference -0·32% [-1·25 to 0·60]) and dornase alfa trial (0·18% [-0·38 to 0·74] in the discontinuation group [n=199] vs -0·16% [-0·73 to 0·41] in the continuation group [n=193]; between-group difference 0·35% [-0·45 to 1·14]), with consistent results in the intention-to-treat populations. In the hypertonic saline trial, 64 (35%) of 184 in the discontinuation group versus 44 (24%) of 186 participants in the continuation group and, in the dornase alfa trial, 89 (37%) of 240 in the discontinuation group versus 55 (23%) of 237 in the continuation group had at least one adverse event.

INTERPRETATION

In individuals with cystic fibrosis on ETI with relatively well preserved pulmonary function, discontinuing daily hypertonic saline or dornase alfa for 6 weeks did not result in clinically meaningful differences in pulmonary function when compared with continuing treatment.

Characterizing CFTR modulated sweat chloride response across the cf population: Initial results from the CHEC-SC study

BACKGROUND

CHEC-SC is an ongoing epidemiologic study characterizing modulator-induced sweat chloride (SC) responses across the CF population, with interim results available prior to the availability of triple combination modulator therapy.

METHODS

Eligible participants had been prescribed a modulator for ≥90 days with re-enrollment allowed upon establishment of a new modulator. Pre-modulator SC values were obtained from chart review; post-modulator sweat was collected and analyzed locally. SC changes were descriptively summarized with biologic sex effects adjusted for age, weight, and CFTR genotype. Heterogeneity in ivacaftor SC response was characterized in relation to published CFTR functional responses.

RESULTS

1848 participants provided 2004 SC measurements, 26.2% on ivacaftor, 39.1% on lumacaftor/ivacaftor, and 34.7% on tezacaftor/ivacaftor. Average SC changes for all modulators were consistent with those reported in previous clinical studies, with greater variation in SC response observed among rarer mutations and notable shifts in the proportion with SC <60mmol/L independent of the magnitude of SC change. Ivacaftor induced in vitro CFTR functional change was significantly correlated with ivacaftor-modulated SC response (Pearson correlation= ‒0.52, 95% CI: ‒0.773, ‒0.129). Average SC change from ivacaftor to tezacaftor/ivacaftor was ‒4.9 mmol/L (n=17,95% CI:‒9.3, ‒0.5) and differed from those switching from lumacaftor/ivacaftor (10.0 mmol/L, n=139, 95% CI:7.8,12.3). Sex at birth was not associated with SC response.

CONCLUSIONS

CHEC-SC is the largest study characterizing modulator-induced SC changes across the CF population. There was a strong association between ivacaftor induced in vitro CFTR function and SC response across a genotypically heterogenous cohort. Biological sex was not associated with SC response.

Impact of azithromycin on serum inflammatory markers in children with cystic fibrosis and new Pseudomonas

Chronic azithromycin improves outcomes in cystic fibrosis (CF), but its mechanism of action is unclear. The OPTIMIZE trial demonstrated improvement in time to first pulmonary exacerbation in children with new Pseudomonas treated with azithromycin. Azithromycin effect on systemic markers of inflammation over 18 months was assessed by change from baseline for high-sensitivity C-reactive protein, myeloperoxidase, calprotectin and absolute neutrophil count in the OPTIMIZE population. Subjects treated with chronic azithromycin or placebo had samples collected at baseline, 39 and 78 weeks of treatment. In 129 subjects, a significant decrease in high-sensitivity C-reactive protein was present at 39 weeks in the azithromycin group compared to placebo, but no significant difference between the groups at 78 weeks. No differences in change from baseline in myeloperoxidase, calprotectin or absolute neutrophil count were present at either time point. This supports the concept of a transient immunomodulatory effect for chronic azithromycin therapy in children with CF.

Development and Internal Validation of a Prognostic Model of the Probability of Death or Lung Transplantation Within 2 Years for Patients With Cystic Fibrosis and FEV1 ≤ 50% Predicted

BACKGROUND

Improved methods are needed to risk-stratify patients with cystic fibrosis (CF) and reduced FEV1.

RESEARCH QUESTIONS

What are the predictors of death or lung transplantation (LTx) within 2 years among patients with CF whose FEV1 ≤ 50% predicted? Do these markers similarly predict outcomes among G551D patients taking ivacaftor since 2012?

STUDY DESIGN AND METHODS

Patients with CF, age ≥ 6 years with FEV1 ≤ 50% predicted as of December 31, 2014, were identified in a data set that merged Cystic Fibrosis Foundation and United Network for Organ Sharing (UNOS) registries. The least absolute shrinkage and selection operator (LASSO) method was applied to a randomly selected training set to select important prognostic variables. Accuracy and association of the model with death or LTx with 2 years (2-year death or LTx) were validated via logistic regression on an independent test set. Sensitivity analyses explored predictors for patients with UNOS data.

RESULTS

FEV1 percent predicted (OR, 1.51 for 5% decrease; 95% CI, 1.27-1.81), number of pulmonary exacerbations treated with IV antibiotics (OR, 1.35; 95% CI, 1.11-1.65), and continuous or nocturnal oxygen (OR, 3.71; 95% CI, 1.81-7.59) were significantly associated with 2-year death or LTx. Our model predicted outcomes with greater sensitivity (ratio of sensitivity, 1.26; 95% CI, 1.02-1.54), ratio of positive predictive value (1.25; 95% CI, 1.05-1.51), and ratio of negative predictive value (1.04; 95% CI, 1.01-1.07) than FEV1 < 30% predicted. Among those taking ivacaftor in 2014, only FEV1 remained associated with 2-year death or LTx. For patients with UNOS data, LASSO identified additional covariates of interest, including noninvasive ventilation use, low hemoglobin, pulmonary arterial systolic pressure, supplemental oxygen, mechanical ventilation, FEV1 percent predicted, and cardiac index.

INTERPRETATION

Among individuals with CF and FEV1 ≤ 50% predicted, FEV1 percent predicted, oxygen therapy, and number of pulmonary exacerbations predicted 2-year death or LTx. Although limited by small sample size, only FEV1 remained predictive in patients receiving highly effective modulator therapy. Additional physiologic variables could improve prognostication in CF.

Testing the effects of combining azithromycin with inhaled tobramycin for P. aeruginosa in cystic fibrosis: a randomised, controlled clinical trial

RATIONALE

Inhaled tobramycin and oral azithromycin are common chronic therapies in people with cystic fibrosis and Pseudomonas aeruginosa airway infection. Some studies have shown that azithromycin can reduce the ability of tobramycin to kill P. aeruginosa. This trial was done to test the effects of combining azithromycin with inhaled tobramycin on clinical and microbiological outcomes in people already using inhaled tobramycin. We theorised that those randomised to placebo (no azithromycin) would have greater improvement in forced expiratory volume in one second (FEV1) and greater reduction in P. aeruginosa sputum in response to tobramycin.

METHODS

A 6-week prospective, randomised, placebo-controlled, double-blind trial testing oral azithromycin versus placebo combined with clinically prescribed inhaled tobramycin in individuals with cystic fibrosis and P. aeruginosa airway infection.

RESULTS

Over a 6-week period, including 4 weeks of inhaled tobramycin, the relative change in FEV1 did not statistically significantly differ between groups (azithromycin (n=56) minus placebo (n=52) difference: 3.44%; 95% CI: -0.48 to 7.35; p=0.085). Differences in secondary clinical outcomes, including patient-reported symptom scores, weight and need for additional antibiotics, did not significantly differ. Among the 29 azithromycin and 35 placebo participants providing paired sputum samples, the 6-week change in P. aeruginosa density differed in favour of the placebo group (difference: 0.75 log10 CFU/mL; 95% CI: 0.03 to 1.47; p=0.043).

CONCLUSIONS

Despite having greater reduction in P. aeruginosa density in participants able to provide sputum samples, participants randomised to placebo with inhaled tobramycin did not experience significantly greater improvements in lung function or other clinical outcomes compared with those randomised to azithromycin with tobramycin.

Prospectively evaluating maternal and fetal outcomes in the era of CFTR modulators: the MAYFLOWERS observational clinical trial study design

Introduction

Therapeutic advances have markedly increased life expectancy for those with cystic fibrosis (CF), resulting in a median predicted survival over 50 years. Consequently, people with CF (pwCF) are living through their reproductive years and the rate of pregnancy is rapidly rising. Despite the increased relevance of this topic, multicentre studies investigating the association between maternal health and choices made during pregnancy on maternal and fetal outcomes do not exist. Furthermore, there are very limited data on the outcomes following CF transmembrane conductance regulator (CFTR) modulator use during pregnancy and lactation.

Methods and analysis

Maternal and Fetal Outcomes in the Era of Modulators (MAYFLOWERS) is a prospective, multicentre observational clinical trial which will enrol approximately 285 pregnant pwCF including those who are modulator ineligible and those who choose to continue or discontinue CFTR modulator therapy during pregnancy and lactation. The primary aim of this 35-month study is to assess whether lung function changes during pregnancy differ based on the continued use of modulators or other factors such as pre-existing comorbid conditions. Secondary objectives include evaluation of pregnancy related and obstetrical complications and changes in mental health.

Ethics and dissemination

The design of this study required special consideration of study burden on pregnant and lactating people with chronic illness in the setting of a substantial number of unanswered questions under these conditions. MAYFLOWERS is the first prospective clinical trial examining pregnancy in CF; the outcomes will guide providers on pregnancy management in pwCF and others with chronic respiratory disease.

Validation of the French 3-year prognostic score for death or lung transplant in the United States cystic fibrosis population

In 2017, Nkam et al. published a prognostic score to predict death or lung transplant within 3 years among adult cystic fibrosis (CF) patients. Their model was developed using French CF registry data and was subsequently validated in the Canadian CF registry. We evaluated this prognostic score using data from adult patients with CF in the United States (US) CF Foundation Patient registry, combined with lung transplant records from the United Network for Organ Sharing (UNOS) Registry (2013 to 2016) (n=11,542). We found that the prognostic score had a very good discriminative index predicting death or lung transplant in the US CF population (AUC 0.88, 95% CI 0.88-0.89) with an odds ratio (OR) of 2.83 (95% CI 2.69 - 2.97) for each unit increase in the score. However, it did not provide significant additional utility over an FEV1 ≤30% of predicted as a predictor of death or lung transplant.

A new path for CF clinical trials through the use of historical controls

BACKGROUND

Given future challenges in conducting large randomized, placebo controlled trials for future CF therapeutics development, we evaluated the potential for using external historical controls to either enrich or replace traditional concurrent placebo groups in CF trials.

METHODS

The study included data from sequentially completed, randomized, controlled clinical trials, EPIC and OPTIMIZE respectively, evaluating optimal antibiotic therapy to reduce the risk of pulmonary exacerbation in children with early Pseudomonas aeruginosa infection. The primary treatment effect in OPTIMIZE, the risk of pulmonary exacerbation associated with azithromycin, was re-estimated in alternative designs incorporating varying numbers of participants from the earlier trial (EPIC) as historical controls. Bias and precision of these estimates were characterized. Propensity scores were derived to adjust for baseline differences across study populations, and both Poisson and Cox regression were used to estimate treatment efficacy.

RESULTS

Replacing 86 OPTIMIZE placebo participants with 304 controls from EPIC to mimic a fully historically controlled trial resulted an 8% reduction in risk of pulmonary exacerbations (Hazard ratio (HR):0.92 95% CI 0.61, 1.34) when not adjusting for key baseline differences between study populations. After adjustment, a 37% decrease in risk of exacerbation (HR:0.63, 95% CI 0.50, 0.80) was estimated, comparable to the estimate from the original trial comparing the 86 placebo participants to 77 azithromycin participants on azithromycin (45%, HR:0.55, 95% CI: 0.34, 0.86). Other adjusted approaches provided similar estimates for the efficacy of azithromycin in reducing exacerbation risk: pooling all controls from both studies provided a HR of 0.60 (95% x`CI 0.46, 0.77) and augmenting half the OPTIMIZE placebo participants with EPIC controls gave a HR 0.63 (95% CI 0.48, 0.82).

CONCLUSIONS

The potential exists for future CF trials to utilize historical control data. Careful consideration of both the comparability of controls and of optimal methods can reduce the potential for biased estimation of treatment effects.

The impact of SARS-CoV-2 on the cystic fibrosis foundation therapeutics development network

The Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) global pandemic significantly impacted CF clinical research within the Cystic Fibrosis Foundation Therapeutics Development Network (CFF TDN). A Research Electronic Data Capture (REDCap) survey was developed and sent to network sites to monitor and understand the impact on research teams, ongoing and anticipated clinical research, and specific clinical and research procedures. Key findings indicated an early impact on participant enrollment, research team stability, and procedures such as spirometry and sputum induction. These trends steadily improved over the months as research activities began to recover across the TDN. While SARS-CoV-2 created a significant challenge it also highlights new opportunities to expand CF research with greater focus on data collection outside of research centers and increased access for remote participation.

Measuring the impact of CFTR modulation on sweat chloride in cystic fibrosis: Rationale and design of the CHEC-SC study

BACKGROUND

The Characterizing CFTR Modulated Changes in Sweat Chloride and their Association with Clinical Outcomes (CHEC-SC) study is a large epidemiologic study designed to determine the relationship between sweat chloride response and clinical outcomes in people with cystic fibrosis (CF) on commercially approved CFTR modulators. A challenge to study feasibility was capturing sweat chloride measurements before modulator initiation. We tested the hypothesis that historic sweat chloride approximated contemporary pre-modulator values to estimate CFTR modulator-induced changes, allowing a single-visit study design.

METHODS

GOAL and PROSPECT were multi-center prospective studies of individuals initiating ivacaftor or lumacaftor-ivacaftor. At enrollment, pre-modulator sweat chloride was measured and historic results recorded. Post-modulator sweat chloride was measured at 1, 3 and 6 months. For this analysis, differences between historic and pre-modulator sweat chloride were estimated. CFTR modulator-induced sweat chloride mean changes were compared using historic and pre-modulator sweat chloride.

RESULTS

Paired historic and pre-modulator sweat chloride (n=406 participants) revealed a non-significant mean change of -1.0 mmol/L (95% CI: -2.71, 0.66) over an average of 17.2 years. Calculating sweat response to ivacaftor or lumacaftor-ivacaftor using historic or pre-modulator values resulted in similar estimates of modulator response. Based on these results, the CHEC-SC study was designed with a single, post-modulator sweat chloride measurement.

CONCLUSIONS

Historic sweat chloride values provide a reliable estimate of pre-modulator sweat chloride for people starting on modulator therapy. The CHEC-SC study anticipates capturing approximately 5,000 sweat chloride values, providing an unprecedented understanding of sweat chloride across the CF population in the era of CFTR modulators.

Long-term azithromycin use is not associated with QT prolongation in children with cystic fibrosis

Chronic Azithromycin (AZM) is a common treatment for lung infection. Among adults at risk of cardiac events, AZM use has been associated with cardiovascular harm. We assessed cardiovascular safety of AZM among children with CF, as a secondary analysis of a placebo-controlled, clinical trial, in which study drug was taken thrice-weekly for a planned 18 months. Safety assessments using electrocardiogram (ECG) occurred at study enrollment, and then after 3 weeks and 18 months of participation. Among 221 study participants with a median of 18 months follow-up, increased corrected QT interval (QTc) of ≥30 msec was rare, at 3.4 occurrences per 100 person-years; and incidence of QTc prolongation was no higher in the AZM arm than the placebo arm (1.8 versus 5.4 per 100 person-years). No persons experienced QTc intervals above 500 msec. Long-term chronic AZM use was not associated with increased QT prolongation.

Cystic Fibrosis: Emergence of Highly Effective Targeted Therapeutics and Potential Clinical Implications

Cystic fibrosis (CF) remains the most common life-shortening hereditary disease in white populations, with high morbidity and mortality related to chronic airway mucus obstruction, inflammation, infection, and progressive lung damage. In 1989, the discovery that CF is caused by mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) gene that encodes a cAMP-dependent anion channel vital for proper Cl^- and HCO₃^- transport across epithelial surfaces provided a solid foundation for unraveling underlying disease mechanisms and the development of therapeutics targeting the basic defect in people with CF. In this review, we focus on recent advances in our understanding of the molecular defects caused by different classes of CFTR mutations, implications for pharmacological rescue of mutant CFTR, and insights into how CFTR dysfunction impairs key host defense mechanisms, such as mucociliary clearance and bacterial killing in CF airways. Furthermore, we review the path that led to the recent breakthrough in the development of highly effective CFTR-directed therapeutics, now applicable for up to 90% of people with CF who carry responsive CFTR mutations, including those with just a single copy of the most common F508del mutation. Finally, we discuss the remaining challenges and strategies to develop highly effective targeted therapies for all patients and the unprecedented potential of these novel therapies to transform CF from a fatal to a treatable chronic condition.

Building global development strategies for cf therapeutics during a transitional cftr modulator era

As CFTR modulator therapy transforms the landscape of cystic fibrosis (CF) care, its lack of uniform access across the globe combined with the shift towards a new standard of care creates unique challenges for the development of future CF therapies. The advancement of a full and promising CF therapeutics pipeline remains a necessary priority to ensure maximal clinical benefits for all people with CF. It is through collaboration across the global CF community that we can optimize the evaluation and approval process of new therapies. To this end, we must identify areas for which harmonization is lacking and for which efficiencies can be gained to promote ethical, feasible, and credible study designs amidst the changing CF care landscape. This article summarizes the counsel from core advisors across multiple international regions and clinical trial networks, developed during a one-day workshop in October 2019. The goal of the workshop was to identify, in consideration of the highly transitional era of CFTR modulator availability, the drug development areas for which global alignment is currently uncertain, and paths forward that will enable advancement of CF therapeutic development.

Rapid lung function decline in adults with early-stage cystic fibrosis lung disease

RATIONALE

The prevalence of adults living with cystic fibrosis (CF) who have early-stage lung disease is increasing.

OBJECTIVES

Describe the prevalence and evaluate spirometric risk factors associated with the subgroup of patients with early-stage lung disease and FEV₁ decline of ≥5% predicted/year.

METHODS

Retrospective cohort study of patients ≥18 years with FEV₁% predicted ≥80% included in the US CF Foundation Patient Registry from 2010-2013. Regression models were developed to estimate FEV₁ rate of decline. Multivariable logistic analysis was used to assess if spirometric risk factors were associated with FEV₁ decline.

MEASUREMENTS AND MAIN RESULTS

3,029 subjects were in the study cohort. Approximately 15% of the cohort had a substantial decline in lung function ≥5% predicted/year. In multivariable models adjusted for confounders, FEV₁/FVC ratio <0.8 (Odds Ratio (OR) 1.63, 95% confidence interval (CI) 1.31 to 2.02) and history of FEV₁% predicted variability (OR 2.35,95%CI 1.74 to 3.18) were associated with rapid lung function decline.

CONCLUSIONS

Even among adults with early-stage lung disease, approximately 15% are shown to progress and experience a large decline in lung function. This reinforces the concept that lung function in early-stage CF is not normal or mild. Rather, lung function decline may be delayed, but not avoided, in these individuals. Variability in FEV₁% predicted and airway obstruction as measured by FEV1/FVC ratio may identify individuals at increased risk of decline. Adults with early-stage lung disease should be followed in clinic to monitor for onset of decline.

A Novel Tool to Evaluate the Accuracy of Predicting Survival and Guiding Lung Transplantation in Cystic Fibrosis

Background

Effective transplantation recommendations in cystic fibrosis (CF) require accurate survival predictions, so that high-risk patients may be prioritized for transplantation. In practice, decisions about transplantation are made dynamically, using routinely updated assessments. We present a novel tool for evaluating risk prediction models that, unlike traditional methods, captures classification accuracy in identifying high-risk patients in a dynamic fashion.

Methods

Predicted risk is used as a score to rank incident deaths versus patients who survive, with the goal of ranking the deaths higher. The mean rank across deaths at a given time measures time-specific predictive accuracy; when assessed over time, it reflects time-varying accuracy.

Results

Applying this approach to CF Registry data on patients followed from 1993-2011, we show that traditional methods do not capture the performance of models used dynamically in the clinical setting. Previously proposed multivariate risk scores perform no better than forced expiratory volume in 1 second as a percentage of predicted normal (FEV₁%) alone. Despite its value for survival prediction, FEV₁% has a low sensitivity of 45% over time (for fixed specificity of 95%), leaving room for improvement in prediction. Finally, prediction accuracy with annually-updated FEV₁% shows minor differences compared to FEV₁% updated every 2 years, which may have clinical implications regarding the optimal frequency of updating clinical information.

Conclusions

It is imperative to continue to develop models that accurately predict survival in CF. Our proposed approach can serve as the basis for evaluating the predictive ability of these models by better accounting for their dynamic clinical use.

Reinfection rates following adherence to Infectious Diseases Society of America guideline recommendations in first cerebrospinal fluid shunt infection treatment

OBJECTIVECSF shunt infection treatment requires both surgical and antibiotic decisions. Using the Hydrocephalus Clinical Research Network (HCRN) Registry and 2004 Infectious Diseases Society of America (IDSA) guidelines that were not proactively distributed to HCRN providers, the authors previously found high adherence to surgical recommendations but poor adherence to intravenous (IV) antibiotic duration recommendations. In general, IV antibiotic duration was longer than recommended. In March 2017, new IDSA guidelines expanded upon the 2004 guidelines by including recommendations for selection of specific antibiotics. The objective of this study was to describe adherence to both 2004 and 2017 IDSA guideline recommendations for CSF shunt infection treatment, and to report reinfection rates associated with adherence to guideline recommendations.METHODSThe authors investigated a prospective cohort of children younger than 18 years of age who underwent treatment for first CSF shunt infection at one of 7 hospitals from April 2008 to December 2012. CSF shunt infection was diagnosed by recovery of bacteria from CSF culture (CSF-positive infection). Adherence to 2004 and 2017 guideline recommendations was determined. Adherence to antibiotics was further classified as longer or shorter duration than guideline recommendations. Reinfection rates with 95% confidence intervals (CIs) were generated.RESULTSThere were 133 children with CSF-positive infections addressed by 2004 IDSA guideline recommendations, with 124 at risk for reinfection. Zero reinfections were observed among those whose treatment was fully adherent (0/14, 0% [95% CI 0%-20%]), and 15 reinfections were observed among those whose infection treatment was nonadherent (15/110, 14% [95% CI 8%-21%]). Among the 110 first infections whose infection treatment was nonadherent, 74 first infections were treated for a longer duration than guidelines recommended and 9 developed reinfection (9/74, 12% [95% CI 6%-22%]). There were 145 children with CSF-positive infections addressed by 2017 IDSA guideline recommendations, with 135 at risk for reinfection. No reinfections were observed among children whose treatment was fully adherent (0/3, 0% [95% CI 0%-64%]), and 18 reinfections were observed among those whose infection treatment was nonadherent (18/132, 14% [95% CI 8%-21%]).CONCLUSIONSThere is no clear evidence that either adherence to IDSA guidelines or duration of treatment longer than recommended is associated with reduction in reinfection rates. Because IDSA guidelines recommend shorter IV antibiotic durations than are typically used, improvement efforts to reduce IV antibiotic use in CSF shunt infection treatment can and should utilize IDSA guidelines.

Azithromycin for Early Pseudomonas Infection in Cystic Fibrosis. The OPTIMIZE Randomized Trial

RATIONALE

New isolation of Pseudomonas aeruginosa (Pa) is generally treated with inhaled antipseudomonal antibiotics such as tobramycin inhalation solution (TIS). A therapeutic approach that complements traditional antimicrobial therapy by reducing the risk of pulmonary exacerbation and inflammation may ultimately prolong the time to Pa recurrence.

OBJECTIVES

To test the hypothesis that the addition of azithromycin to TIS in children with cystic fibrosis and early Pa decreases the risk of pulmonary exacerbation and prolongs the time to Pa recurrence.

METHODS

The OPTIMIZE (Optimizing Treatment for Early Pseudomonas aeruginosa Infection in Cystic Fibrosis) trial was a multicenter, double-blind, randomized, placebo-controlled, 18-month trial in children with CF, 6 months to 18 years of age, with early Pa. Azithromycin or placebo was given 3× weekly with standardized TIS.

MEASUREMENTS AND MAIN RESULTS

The primary endpoint was the time to pulmonary exacerbation requiring antibiotics and the secondary endpoint was the time to Pa recurrence, in addition to other clinical and safety outcomes. A total of 221 participants (111 placebo, 110 azithromycin) out of a planned 274 were enrolled. Enrollment was stopped early by the NHLBI because the trial had reached the prespecified interim boundary for efficacy. The risk of pulmonary exacerbation was reduced by 44% in the azithromycin group as compared with the placebo group (hazard ratio, 0.56; 95% confidence interval, 0.37-0.83; P = 0.004). Weight increased by 1.27 kg in the azithromycin group compared with the placebo group (95% confidence interval, 0.01-2.52; P = 0.046). No significant differences were seen in microbiological or other clinical or safety endpoints.

CONCLUSIONS

Azithromycin was associated with a significant reduction in the risk of pulmonary exacerbation and a sustained improvement in weight, but had no impact on microbiological outcomes in children with early Pa. Clinical trial registered with clinicaltrials.gov (NCT02054156).

Changing Rates of Chronic Pseudomonas aeruginosa Infections in Cystic Fibrosis: A Population-Based Cohort Study

Background

Chronic Pseudomonas aeruginosa lung infection is associated with significant morbidity and mortality in cystic fibrosis (CF). It is not known whether recent advances in care have affected the rates of chronic infection. We aimed to determine if the rates of developing new chronic P. aeruginosa infection among adolescents and adults with CF significantly changed over time.

Methods

The cohort consisted of individuals with CF followed in the Cystic Fibrosis Foundation Patient Registry aged ≥13 years without chronic P. aeruginosa at baseline. Multivariable regression models accounting for within-patient correlation were used to assess the change in rate of developing chronic P. aeruginosa infection between 2003 and 2012.

Results

A total of 15504 individuals were followed for a median of 5 (interquartile range, 2-9) years. The annual rates of developing new chronic P. aeruginosa decreased from 14.3% in 2003 to 6.4% in 2012. After adjusting for potential confounders, relative risk (RR) of developing chronic P. aeruginosa infection decreased significantly over time compared to 2003 (P value test of trend < .001). Compared with 2003, the RR of developing chronic P. aeruginosa infection in 2012 was 0.33 (95% confidence interval, 0.30-0.37). No significant increases in risk of chronic infections with other major CF bacterial pathogens relative to 2003 were identified.

Conclusions

Among individuals with CF, a significant decrease in the risk and rates of developing chronic P. aeruginosa infection between 2003 and 2012 was observed. Whether this decline results in changes in clinical outcomes warrants further exploration.

Patient and Treatment Characteristics by Infecting Organism in Cerebrospinal Fluid Shunt Infection

BACKGROUND

Previous studies of cerebrospinal fluid (CSF) shunt infection treatment have been limited in size and unable to compare patient and treatment characteristics by infecting organism. Our objective was to describe variation in patient and treatment characteristics for children with first CSF shunt infection, stratified by infecting organism subgroups outlined in the 2017 Infectious Disease Society of America's (IDSA) guidelines.

METHODS

We studied a prospective cohort of children <18 years of age undergoing treatment for first CSF shunt infection at one of 7 Hydrocephalus Clinical Research Network hospitals from April 2008 to December 2012. Differences between infecting organism subgroups were described using univariate analyses and Fisher's exact tests.

RESULTS

There were 145 children whose infections were diagnosed by CSF culture and addressed by IDSA guidelines, including 47 with Staphylococcus aureus, 52 with coagulase-negative Staphylococcus, 37 with Gram-negative bacilli, and 9 with Propionibacterium acnes. No differences in many patient and treatment characteristics were seen between infecting organism subgroups, including age at initial shunt, gender, race, insurance, indication for shunt, gastrostomy, tracheostomy, ultrasound, and/or endoscope use at all surgeries before infection, or numbers of revisions before infection. A larger proportion of infections were caused by Gram-negative bacilli when antibiotic-impregnated catheters were used at initial shunt placement (12 of 23, 52%) and/or subsequent revisions (11 of 23, 48%) compared with all other infections (9 of 68 [13%] and 13 of 68 [19%], respectively). No differences in reinfection were observed between infecting organism subgroups.

CONCLUSIONS

The organism profile encountered at infection differs when antibiotic-impregnated catheters are used, with a higher proportion of Gram-negative bacilli. This warrants further investigation given increasing adoption of antibiotic-impregnated catheters.

Reinfection after treatment of first cerebrospinal fluid shunt infection: a prospective observational cohort study

OBJECTIVE CSF shunt infection requires both surgical and antibiotic treatment. Surgical treatment includes either total shunt removal with external ventricular drain (EVD) placement followed by new shunt insertion, or distal shunt externalization followed by new shunt insertion once the CSF is sterile. Antibiotic treatment includes the administration of intravenous antibiotics. The Hydrocephalus Clinical Research Network (HCRN) registry provides a unique opportunity to understand reinfection following treatment for CSF shunt infection. This study examines the association of surgical and antibiotic decisions in the treatment of first CSF shunt infection with reinfection. METHODS A prospective cohort study of children undergoing treatment for first CSF infection at 7 HCRN hospitals from April 2008 to December 2012 was performed. The HCRN consensus definition was used to define CSF shunt infection and reinfection. The key surgical predictor variable was surgical approach to treatment for CSF shunt infection, and the key antibiotic treatment predictor variable was intravenous antibiotic selection and duration. Cox proportional hazards models were constructed to address the time-varying nature of the characteristics associated with shunt surgeries. RESULTS Of 233 children in the HCRN registry with an initial CSF shunt infection during the study period, 38 patients (16%) developed reinfection over a median time of 44 days (interquartile range [IQR] 19-437). The majority of initial CSF shunt infections were treated with total shunt removal and EVD placement (175 patients; 75%). The median time between infection surgeries was 15 days (IQR 10-22). For the subset of 172 infections diagnosed by CSF culture, the mean ± SD duration of antibiotic treatment was 18.7 ± 12.8 days. In all Cox proportional hazards models, neither surgical approach to infection treatment nor overall intravenous antibiotic duration was independently associated with reinfection. The only treatment decision independently associated with decreased infection risk was the use of rifampin. While this finding did not achieve statistical significance, in all 5 Cox proportional hazards models both surgical approach (other than total shunt removal at initial CSF shunt infection) and nonventriculoperitoneal shunt location were consistently associated with a higher hazard of reinfection, while the use of ultrasound was consistently associated with a lower hazard of reinfection. CONCLUSIONS Neither surgical approach to treatment nor antibiotic duration was associated with reinfection risk. While these findings did not achieve statistical significance, surgical approach other than total removal at initial CSF shunt infection was consistently associated with a higher hazard of reinfection in this study and suggests the feasibility of controlling and standardizing the surgical approach (shunt removal with EVD placement). Considerably more variation and equipoise exists in the duration and selection of intravenous antibiotic treatment. Further consideration should be given to the use of rifampin in the treatment of CSF shunt infection. High-quality studies of the optimal duration of antibiotic treatment are critical to the creation of evidence-based guidelines for CSF shunt infection treatment.

Home Monitoring of Patients with Cystic Fibrosis to Identify and Treat Acute Pulmonary Exacerbations. eICE Study Results

RATIONALE

Individuals with cystic fibrosis (CF) experience frequent acute pulmonary exacerbations, which lead to decreased lung function and reduced quality of life.

OBJECTIVES

The goal of this study was to determine if an intervention directed toward early detection of pulmonary exacerbations using home spirometry and symptom monitoring would result in slower decline in lung function than in control subjects.

METHODS

We conducted a multicenter, randomized trial at 14 CF centers with subjects at least 14 years old. The early intervention arm subjects measured home spirometry and symptoms electronically twice per week. Sites were notified if a participant met criteria for an exacerbation and contacted participants to determine if treatment for acute exacerbation was required. Participants in the usual care arm were seen every 3 months and were asked to contact the site if they were concerned about worsening pulmonary symptoms.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the 52-week change in FEV₁. Secondary outcomes included time to first exacerbation and subsequent exacerbation, quality of life, and change in weight. A total of 267 patients were randomized, and the study arms were well matched at baseline. There was no significant difference between study arms in 52-week mean change in FEV₁ slope (mean slope difference, 0.00 L, 95% confidence interval, -0.07 to 0.07; P = 0.99). The early intervention arm subjects detected exacerbations more frequently than usual care arm subjects (time to first exacerbation hazard ratio, 1.45; 95% confidence interval, 1.09 to 1.93; P = 0.01). Adverse events were not significantly different between treatment arms.

CONCLUSIONS

An intervention of home monitoring among patients with CF was able to detect more exacerbations than usual care, but this did not result in slower decline in lung function. Clinical trial registered with www.clinicaltrials.gov (NCT01104402).

Lung function decline is delayed but not decreased in patients with cystic fibrosis and the R117H gene mutation

BACKGROUND

Patients with cystic fibrosis (CF) experience variable lung disease phenotypes. The R117H mutation is often associated with preserved lung function. Our objective was to compare the rate of lung function decline in patients with the R117H mutation and patients homozygous for the F508del mutation.

METHODS

Rate of decline in percentage-of-predicted FEV₁ (ppFEV₁) was analyzed using the 2006-2010 US CF Foundation Patient Registry.

RESULTS

4-year rate of decline was slower in 156 R117H patients compared with 6251 F508del patients (-0.61 vs -2.03 ppFEV₁/year, P<0.001). Rates of decline in children were slower in R117H vs F508del patients (6-12-year-olds: +0.73 vs -1.91 ppFEV₁/year, P<0.001 and 13-17-year-olds: -1.55 vs -2.66 ppFEV₁/year, P=0.046), whereas rates in adults were not significantly different (18-24-year-olds: -1.52 vs -2.12, P=0.26 and ≥25-year-olds: -1.17 vs -1.40, P=0.33).

CONCLUSIONS

These findings are consistent with a delayed onset, but ultimately similar progression, of lung disease in R117H compared with homozygous F508del patients.

Residual Weighted Learning for Estimating Individualized Treatment Rules

Personalized medicine has received increasing attention among statisticians, computer scientists, and clinical practitioners. A major component of personalized medicine is the estimation of individualized treatment rules (ITRs). Recently, Zhao et al. (2012) proposed outcome weighted learning (OWL) to construct ITRs that directly optimize the clinical outcome. Although OWL opens the door to introducing machine learning techniques to optimal treatment regimes, it still has some problems in performance. (1) The estimated ITR of OWL is affected by a simple shift of the outcome. (2) The rule from OWL tries to keep treatment assignments that subjects actually received. (3) There is no variable selection mechanism with OWL. All of them weaken the finite sample performance of OWL. In this article, we propose a general framework, called Residual Weighted Learning (RWL), to alleviate these problems, and hence to improve finite sample performance. Unlike OWL which weights misclassification errors by clinical outcomes, RWL weights these errors by residuals of the outcome from a regression fit on clinical covariates excluding treatment assignment. We utilize the smoothed ramp loss function in RWL, and provide a difference of convex (d.c.) algorithm to solve the corresponding non-convex optimization problem. By estimating residuals with linear models or generalized linear models, RWL can effectively deal with different types of outcomes, such as continuous, binary and count outcomes. We also propose variable selection methods for linear and nonlinear rules, respectively, to further improve the performance. We show that the resulting estimator of the treatment rule is consistent. We further obtain a rate of convergence for the difference between the expected outcome using the estimated ITR and that of the optimal treatment rule. The performance of the proposed RWL methods is illustrated in simulation studies and in an analysis of cystic fibrosis clinical trial data.