The National Emphysema Treatment Trial: summary and update.

Surgery for severe emphysema involves a cohort of patients who are already at risk for increased perioperative morbidity and mortality. Through the careful screening and selection process, improved intraoperative techniques and rigorous attention to postoperative care, the NETT managed to yield acceptable improvements in survival and functional outcomes in this fragile patient cohort and these benefits were sustained over the long-term. Identification of the characteristics associated with a higher risk of death has provided tangible patient selection criteria for the ongoing application of LVRS. Because the NETT was such a large-scale study, the protocols that were developed had to be standardized across several centers. This produced reliable and reproducible standards for evaluation and treatment that can be applied to the surgical treatment of emphysema. When considering these criteria, although individualized patient selection is important, only patients with upper-lobe predominant disease on chest CT and possibly those with non-upper-lobe predominant disease who also have low baseline exercise capacity are appropriate candidates for LVRS. Expectedly, questions remain regarding the exact mechanism whereby the benefits derived from LVRS are obtained. Additionally, the benefit of LVRS in patients with heterogeneous but non-upper-lobe predominant disease remains to be further elucidated. In spite of the limitations of the study, the NETT, through a tremendous coordinated effort, provided valuable outcomes data, answered the pressing questions regarding lung volume reduc-tion surgery that existed at the time, and provided valuable insight into other facets of emphysema physiology and management through direct observation. Based on the NETT findings, in November 2003, CMS published criteria for expanded coverage for LVRS to include non-high-risk patients who demonstrated either upper-lobe predominant emphysema, or non-upper-lobe predominant emphysema and low baseline exercise capacity and who met the screening guidelines.29 This study not only provided data regarding the clinical efficacy of LRVS, but it was instrumental in determining health policy guidelines for the surgical management of emphysema.