NEW YORK, New York — Despite significant baseline differences, the disease progression and the outcomes at 5 years are similar in those with nontuberculous mycobacteria (NTM) infection relative to those with bronchiectasis but without NTM, according to data at the 6th World Bronchiectasis & NTM Conference (WBC) 2023.
"The outcomes, including exacerbations, hospitalizations, rate of lung function loss, and mortality were similar across the 5-year period," reported Timothy R. Aksamit, MD, a pulmonologist, internist, and critical care medicine specialist at Mayo Clinic, Rochester, Minnesota.
Fifteen years after it started enrolling patients, the US-based Bronchiectasis and NTM Research Registry now has a sufficient number of patients followed over time to compare baseline characteristics and outcomes of these conditions. When the not-yet-published data were presented, several experts expressed surprise, including the new chair of the registry.
"I would not have expected the comparable outcomes in long-term follow-up," said Mark L. Metersky, MD, director, Center for Bronchiectasis Care, University of Connecticut, Farmington. His suspicion had been that NTM patients have a more difficult course.
In the registry, almost 6000 patients with bronchiectasis or NTM are now enrolled. This analysis was confined to the 2634 patients followed for at least 5 years. Of these, 1549 (58.8%) had bronchiectasis and the remaining patients had NTM.
There were many significant differences between the two groups at baseline. Those with NTM were slightly older, had a lower median BMI, and had a higher median FEV1. They also had a statistically lower rate of prior exacerbations and prior hospitalizations, and they were less likely to be infected with Pseudomonas.
NTM patients also were less likely to have asthma, rhinosinusitis, and primary immunodeficiencies, reinforcing the overall picture "that this is really a different cohort," Aksamit said.
Medication use at baseline was also different, including a lower proportion of NTM patients on oral steroids (9% vs 16%; P < .0001) and a much higher proportion on macrolides (41% vs 13%; P < .0001).
Despite the differences in multiple baseline characteristics, the progression of disease and risk of complications was remarkably similar, according to Aksamit. For example, he called the decline in lung function over 5 years as captured with FEV1 to be "nearly superimposable."
The rate of death at 5 years was 12.6% in the NTM group vs 11.5% in the bronchiectasis group, which Aksamit acknowledged is lower for both groups relative to some previously published reports but did not differ significantly between these groups.
On a multivariate analysis of mortality at 5 years, increased mortality was significantly associated with lower FEV1, older age, and greater number of hospitalizations in the previous 2 years. Higher Bronchiectasis Severity Index (BSI) and FACED (an acronym for multiple factors for gauging lung disease severity) scores were both associated with a greater risk of death at 5 years.
"We see much less NTM in Europe, but these data were a surprise to me," commented Eva Polverino, MD, PhD, a pulmonologist associated with the Hospital Clinic of Barcelona, Spain. She had not anticipated that the rates of exacerbations and hospitalizations would be so stable over time, and that differences between NTM and bronchiectasis patients would not be more pronounced given the dissimilarities in the phenotypes.
The reason that NTM is far more common in the United States than Europe or many other parts of the world is unknown. Aksamit said a number of theories have been proposed, including differences in environmental factors or a simple difference in awareness and screening for NTM.
"Many of us think the rates of NTM in other parts of the world will increase if clinicians look harder, but we are not really sure if this is at least part of the reason or not," Aksamit said.
One criticism of the Bronchiectasis and NTM registry is that the enrolling sites have generally been limited to academic centers. This means that data is being generated in the US by those who have already found their way to a tertiary center with expertise in these diseases. The fact that more than 90% of patients in the registry are Caucasian is not believed to be reflective of the epidemiology of these diseases.
"We are aware of this criticism and are now taking steps to create a better sample of patients with these diseases," Aksamit said in an interview. This includes an active effort to expand the registry to include more centers, such as those with clinics in urban areas that have a diverse socioeconomic and racial catchment.
"Registry only takes us so far," acknowledged Aksamit, who reported that there are a variety of plans to expand research capabilities through such steps as linking to Medicare or other sources of data to capture a more real-world cross section of patients.
There are now numerous bronchiectasis registries in other countries, including the EMBARC registry, which is a consortium of sites in 27 countries mostly but not exclusively in Europe. An expanded effort to coordinate between these registries to address a variety of research questions, including those of etiology and treatment, is planned.
Aksamit reported reach funding from multiple pharmaceutical companies at his institution but has disclosed no other relevant financial relationships. Metersky and Polverino have disclosed no relevant financial relationships.
6th World Bronchiectasis & NTM Conference (WBC) 2023. Presented July 19, 2023.
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Cite this: 5-Year Registry Outcomes for Bronchiectasis, NTM Nearly Identical - Medscape - Jul 21, 2023.
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