Percent predicted peak oxygen uptake is superior to weight-indexed peak oxygen uptake in risk stratification before lung cancer lobectomy

Objective To improve preoperative risk stratification in lung cancer lobectomy by identifying and comparing optimal thresholds for peak oxygen uptake (VO2peak) presented as weight-indexed and percent of predicted values, respectively. Methods Longitudinal cohort study including national registry data, on patients scheduled for cancer lobectomy, using available data from preoperative cardiopulmonary exercise testing. The measured VO2peak was indexed by body mass (ml/kg/min) and also compared to two established reference equations (Wasserman-Hansen and SHIP-study, respectively). By receiver operating characteristic analysis, a lower 90% sensitivity and an upper 90% specificity threshold were determined for each measure, in relation to the outcome of any major complication or death. For each measure and based on these thresholds, patients were categorized as low risk, intermediate risk or high risk. The frequency of complications was compared between groups using Chi2. Results The frequency of complications differed significantly between the proposed low, intermediate and high-risk groups when using % predicted SHIP (5%, 21%, 35%, p=0.007) or % predicted Wasserman-Hansen (5%, 25%, 35%, p=0.002), but not when using the weight-indexed VO2peak groups (7%, 23%, 15%, p=0.08). Non-significant differences were found using the threshold <15 ml/kg/min, (p=0.34). Conclusions This study showed that weight-indexed VO2peak was of less use as a marker of risk at the lower range of exercise capacity whereas % predicted VO2peak was associated with a continuously increasing risk of major complications, also at the lower end of exercise capacity. As identifying subjects at high risk of complications is important, % predicted VO2peak is therefore preferable.