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

Vagal activity in patients with metastatic or recurrent breast cancer can predict their survival and it 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 trans-cutaneous 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 entropy and symbolic dynamic non-linear methods. We compared these parameters in patients newly diagnosed with breast cancer, in patients after therapy and in healthy controls. We found lower tcpO2 in patients with presence of malignant tumor compared to those post-treatment and/or without presence of malignancy. We also detected lower 2UV% (two unlike variations) 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 anti-cancer therapy, contrary to tcpO2. Our findings show that breast tissue tcpO2 can recover after the anti-cancer treatment, but complex heart rate control and cardio-vagal regulation remain impaired. This supports the idea that cancer patients and survivors might benefit from non-pharmacological interventions aimed at enhancing vagal activity, such as HRV biofeedback or Yoga.