Criner et al give us Part 1 of a concise clinical review on the lessons learned from the National Emphysema Treatment Trial (NETT), which completed follow-up in December 2002 and whose findings were published in NEJM in 2003. (Part 2 of the concise clinical review is on lung volume reduction surgery.)
The old news: Among 1,218 subjects, NETT showed that lung volume reduction surgery (LVRS) improved survival, exercise capacity and quality of life overall (risk ratio for death at 5 years, 0.86). Subgroup analysis revealed only those with upper lobe-predominant emphysema benefited. The subgroup with upper-lobe predominant emphysema and a low exercise tolerance were most likely to gain a survival benefit, and also improved exercise capacity. Those with upper lobe predominant emphysema and a high exercise tolerance had improvement in exercise capacity and quality of life, but no survival benefit.
Other insights from NETT included:
- Small airways disease (seen on resected lung tissue) is common in people with severe emphysema, and is strongly correlated with COPD progression and mortality.
- Lots of genetic associations identified, with various single nucleotide polymorphisms on various candidate genes potentially contributing to propensity to develop COPD, to have exacerbations, to develop hypoxemia, and with other COPD phenotypes.
- Support for the theory that hyperinflation impairs cardiac performance, and that reducing hyperinflation may improve heart function. This could be a mechanism of the survival benefit of LVRS.
- African-Americans had less anatomic emphysema on CT than white patients, at the same FEV1. Only 3% of the NETT patients were African-American.
- Increase in modified BODE score over time predicted mortality better than any individual variable.
- Pulmonary rehabilitation works, improving exercise capacity, dyspnea, and quality of life. A net 10% of patients were able to go from low- to high-exercise tolerance after prerandomization pulmonary rehab. (The challenge to widespread use of pulmonary rehab remains: getting payers to pay for it.)
Criner GJ et al. The National Emphysema Treatment Trial (NETT). Part I: Lessons Learned about Emphysema. Concise Clinical Review. Am J Respir Crit Care Med 2011;184:763-770.