Cardiovagal regulation and transcutaneous pO2 in breast cancer patients - a pilot study.

Vagal activity of patients with metastatic or recurrent breast cancer can predict their survival and can be altered by behavioral, pharmacological, and surgical interventions. Tumor oxygenation is important in defining the cellular metabolic microenvironment of human malignancies, O2-depleted areas coincide with nutrient and energy deprivation and with a hostile metabolic microenvironment. In our work we simultaneously measured two oxygen-sensitive parameters in breast cancer patients, blood oxygen saturation (SpO2) and transcutaneous O2 partial pressure (tcpO2) in breast tissue. Concurrently, 5-minute beat-to-beat heart rate recording was carried out in order to get heart rate variability (HRV) data from time-domain analyses, frequency-domain analyses, and nonlinear methods - entropy, symbolic dynamics. We compared these parameters in patients newly diagnosed with breast cancer, in patients after therapy and healthy controls. We found lower tcpO2 in patients with presence of malignant tumor compared to those after treatment and/or without presence of malignancy. We detected also lower 2UV% and entropy in non-linear HRV analysis in all breast cancer patients and these parameters associated with parasympathetic activity did not return to the values comparable with healthy individuals after anticancer therapy, contrary to tcpO2. Our findings show that breast tissue tcpO2 can recover after the anticancer treatment, but the complexity of the heart rate control and cardiovagal regulation remain impaired. This supports the idea that cancer patients and survivors might benefit from non-pharmacological interventions aimed at enhancing of vagal activity, e.g. HRV biofeedback or Yoga.