Is Maximal Oxygen Consumption a Good Predictor of Lung Cancer Complications?

Key Point

Exercise capacity, expressed as •Vo2max, is lower in patients who develop clinically relevant complications after curative lung resection, compared with patients without these complications.

Controversy persists regarding whether exercise capacity, expressed as maximal oxygen consumption (•Vo2max), is the best predictor of postoperative cardiopulmonary complications (PPC) after surgical resection in lung cancer patients. However, results from a recent meta-analysis support the utility of •Vo2max for lung cancer patients, as reported in the August Respiratory Medicine.

“After a systematic review of the literature, we found that exercise capacity, expressed as •Vo2max, is lower in patients that develop clinically relevant complications after curative lung resection,” Roberto Benzo, MD, and colleagues stated. “These results are important for the practicing clinician because they answer the literature controversy on the usefulness of measuring preoperative exercise capacity and reinforce the current guidelines on decision making for lung resection.”

Dr. Benzo, of the Division of Pulmonology, Allergy, and Critical Care Medicine at the University of Pittsburgh, and colleagues conducted a meta-analysis of fourteen studies that represented 955 participants. All trials reported preoperative  •Vo2max values (either in mL kg-1 min-1 or percentage of predicted) and involved patients who had experienced PPC. Eleven of these studies reported exercise capacity assessment with a cycle ergometer; two, with treadmills; and the remaining study, with stair climbing.

Patients without PPC had significantly higher levels of •Vo2max in mL kg-1 min-1 when compared with subjects with PPC; this was equivalent to an absolute difference of approximately 3 mL kg-1 min-1. In addition, patients with PPC had significantly higher levels of •Vo2max as a percentage of predicted, when compared with subjects with PPC. There were no statistically significant publication biases; however, the investigators found significant and moderate heterogeneity for these findings, as only observational studies—which tend to have more variety in study outcomes than do randomized controlled trials—were included for the analysis. “Given the intent of our meta-analysis, it was not surprising that no randomized controlled trials on [exercise capacity] could be located since a randomized design is not ethically feasible,” the researchers pointed out.

Secondary outcomes revealed that patients without PPC were approximately four years younger than patients with PPC. In addition, patients without PPC had statistically significantly higher FEV1 and DLCO values than did patients with PPC, although the meta-analysis did not support the view that these two variables are good predictors of complications.

“After the extensive search performed, we found that FEV1 is not consistently reported as an independent predictor of PPC,” Dr. Benzo and colleagues noted. “In addition, the difference found in FEV1 between the complicated and uncomplicated groups (4%) is unlikely to be clinically meaningful.” The investigators also noted that DLCO was shown to be an independent predictor of PPC only in a minority of the publications. “FEV1 and DLCO are currently used as screening methods to detect patients with increased risk of complications but once the patients with increased risk are defined, an exercise capacity measurement is needed to further improve the risk assessment,” Dr. Benzo’s team emphasized.

The investigators acknowledged that lung cancer patients’ best chance for a cure is still surgery, despite the clinical importance of PPC associated with the procedure. “Most would accept even severe complications for a chance at long-term survival,” Dr. Benzo and colleagues stated. However, “[s]ince low exercise capacity is a potentially modifiable risk factor, we posit that an intervention that improves exercise capacity, like pulmonary rehabilitation, could improve patient outcome.”           

—John Merriman

Reference
Benzo R, Kelley GA, Recchi L, et al. Complications of lung resection and exercise capacity: a meta-analysis. Respir Med. 2007;101(8):1790-1797.

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