National Emphysema Treatment Trial (NETT)

The NETT is a five-year, multicenter, randomized study evaluating the safety and effectiveness of lung volume reduction surgery (LVRS) in patients with severe emphysema. As many as two million Americans are estimated to have emphysema, a chronic disabling lung condition.

LVRS has been proposed as a treatment for patients with severe emphysema prior to NETT. Insufficient evidence regarding the safety and effectiveness of the procedure led to a landmark collaboration among three federal agencies within the Department of Health and Human Services: the National Heart, Lung, and Blood Institute; the Centers for Medicare and Medicaid Services; and the Agency for Healthcare Research and Quality. The NETT is the product of that collaboration and may be the model for future evaluation of new medical interventions with large potential medical and financial impact.

The results of NETT will help patients and their physicians make informed decisions regarding LVRS. On average, NETT found that patients with severe emphysema who undergo LVRS and medical therapy are more likely to function better and do not face an increased risk of death compared to those who receive only medical therapy. The results of the LVRS varied substantially among different patient populations, however. Two factors were found to predict the outcome of surgery in individual patients: the distribution of emphysema and the patient’s pre-surgery, post-pulmonary rehabilitation exercise capacity.

Key findings include:

• Patients whose emphysema was predominantly in the upper lobes and whose exercise capacity was low after pulmonary rehabilitation were more likely to function better two years after the surgery then those who received only medical therapy. These patients also appear to have a survival advantage with LVRS.
• Conversely, NETT found characteristics of patients who are poor candidates for LVRS. Patients whose emphysema was not concentrated in the upper lobes of the lung and who had greater exercise capacity (average or better capacity than other NETT participants) were likely to gain little if any benefit from the surgery and were at increased risk for complications or death related to surgery.
• A separate prospective analysis of cost effectiveness of LVRS found that the cost of lung volume reduction surgery is substantial over the short-term, but over the long-term, the procedure may be cost effective if the benefits observed in NETT are sustained.

The Division of Pulmonary and Critical Care Medicine is pleased to have been a major participant in the NETT. While not all patients with severe emphysema benefit from LVRS, NETT has defined characteristics that predict both positive and negative outcomes for LVRS. The Centers for Medicare and Medicaid Services (CMS) is currently deliberating and will issue a LVRS coverage decision within the next several months. Should that decision be positive, patients with severe emphysema will have a new avenue for treatment of their debilitating condition. The Chronic Obstructive Pulmonary Disease Clinic of the Division of Pulmonary and Critical Care Medicine would be pleased to evaluate patients with severe emphysema for LVRS once the CMS coverage decision is made.