Exercise in patients with breast cancer and healthy controls: energy substrate oxidation and blood lactate responses

The aim of this study was to compare select aspects of exercise energy metabolism in patients with breast cancer with that of healthy controls across a variety of exercise intensities. Posttreated patients with breast cancer were matched with healthy women based on age, physical fitness level, and menopausal status. Subjects participated in low-, moderate-, and high-intensity submaximal exercise sessions that corresponded with 40% of maximal oxygen consumption (Vo(2max)), 60% Vo(2max), and 70% Vo(2max). Oxygen consumption and respiratory exchange ratio were taken during submaximal exercise sessions to determine substrate oxidation rates for carbohydrate (CHO) and fat. Blood lactate and blood glucose were also measured before and after each of the submaximal exercise sessions as indices of CHO metabolism. Results indicate that the patients with breast cancer had a significantly (P≤.05) lower CHO oxidation rate and higher fat oxidation rate at all exercise intensities compared with healthy women. The patients with breast cancer had a significantly (P≤.05) lower blood lactate response to exercise across all intensities compared with the healthy women. Glucose responses tended (P<.08) to be more elevated in patients with cancer both before and after the exercise sessions. The findings indicate that posttreated patients with breast cancer have augmented fat metabolism and a reduced CHO-based energy metabolism during submaximal exercise. It is unclear whether these changes are the result of the patient's cancer or their treatment regimen for the cancer.