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NETT REDUX (Accentuating The Positive)
Pablo G. Sanchez, John C. Kucharczuk, Stacey Su, Larry R. Kaiser, Joel D. Cooper; Department of Surgery. Division of Thoracic Surgery. University of Pennsylvania, Philadelphia, PA
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Objective: The National Emphysema Treatment Trial (NETT), a randomized clinical trial, was designed to determinate whether or not bilateral lung volume reduction surgery (LVRS) was more effective than medical management (control group) for selected patients with severe emphysema. A series of arbitrary thresholds for improvement were applied equally to both groups and demonstrated statically significant benefit for LVRS patients in terms of exercise capacity, increase in FEV1 and improvement in health related quality of life (p≤ .001 for each comparison). The established pre-trial hypothesis was that emphysema patients who have “heterogeneously distributed emphysema involving the upper lung zones predominantly” would be most likely to benefit from LVRS. However NETT accrual criteria “were crafted to include all patients who might benefit from LVRS” and therefore included many patients who did not fit the hypothesis. The purpose of this paper is to analyze the outcome of LVRS for the subgroup of patients who met the original NETT hypothesis and to determine the magnitude and duration of benefit for this subgroup.
Methods: Under the Freedom of Information Act, we received and analyzed the NETT data set as of May 2006.
Results: Between January 1998 and July 2002, 571 patients received bilateral LVRS and 562 patients received medical therapy within the trial. Two hundred and sixty one of the LVRS patients (46%) and 250 of the medical therapy patients (44%) met the NETT criteria for heterogeneously distributed upper lobe predominant disease. The 90 day mortality rate for the LVRS group was 5% (13 patients) and for the medical group 1.6% (4 patients). Subsequent mortality at 6 months was 1.5% for the LVRS group and 1.2% for the medical group and at 24 months 7.6% for LVRS and 13.6% for the medical group. Mortality data was complete but the percentage of LVRS and medical patients with missing objective data was 8% and 24% at 6 months; 25% and 42% at 24 months; and 45% and 61% at 36 months respectively. Results in terms of FEV1, Residual Volume (RV), 6 minute walk and dyspnea score are shown in the following table.
Conclusion: For patients with upper lobe predominant emphysema, LVRS provided both statistically and functionally significant improvement in exercise tolerance, measured lung function, dyspnea score and quality of life. These results confirm the hypothesis of the NETT trial and also confirm the results of other non-randomized reports as to the value of LVRS in appropriately selected patients.


Patients with heterogeneous emphysema and UPLP †
LVRS Medical Therapy
Pre-Op(n=261) 6 months(n=224) 24 months(n=167) Pre-Op(n=250) 6 months(n=183) 24 months(n=121)
FEV1
Mean ± SD(L)%pred 0.7±0.327% 1.0±0.437%* 0.9±0.336%* 0.7±0.227% 0.7±0.227% 0.8±0.327%
RV
Mean ± SD(L)%pred 4.9±1.2226% 3.4±1158%* 3.6±1160%* 5.0±1.1227% 5.0±1.2224% 5.0±1.2217%
6 min walk (feet)
Mean ± SD 1166±315 1351±306* 1329±356* 1121±302 1171±317 1142±362
Total score on St George’s RespiratoryQuestionnaire‡
Mean ± SD 56±13 39±21* 42±17* 57±13 56±14 57±14
Total USCD Shortness of Breath Score¶
Mean ± SD 65±19 41±23* 46±24* 66±19 65±20 67±22

* p≤ .001 for paired analyses with Pre-Op scores (two tailed t tests)UPLP: upper lobe predominance, when both upper lobes have the highest HRCT scores in terms of parenchyma destruction. †Difference of 2 points in the HRCT, between the areas of at least 1 lung to define heterogeneity. ‡The St. George’s Respiratory Questionnaire is a 51 item questionnaire on the health -related quality of life with regard to respiratory symptoms. Total score ranges from 0 to 100, with lower scores indicating better health related quality of life.¶ The University of California, San Diego (UCSD), Shortness of Breath Questionnaire is a 24 item questionnaire about dyspnea. The total score ranges from 0 to 120, with lower scores indicating less shortness of breath.
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