Circulating levels of β-endorphin and cortisol in breast cancer.

Neurobehavioral stress can promote the growth and progression of different types of cancer because psychological factors can alter immune and endocrine function. β-endorphin is one of the hormones involved in the bidirectional connection between the immune and neuroendocrine systems that explains the effects of stress on the immune capacity against cancer. Breast cancer (BC) is the most common type of cancer in women and one of the best known to influence the different stressors involved in coping with the disease. Here we evaluated the circulating levels of β-endorphin and cortisol in premenopausal and postmenopausal women with BC treated or not with neoadjuvant chemotherapy, to understand the neuroendocrine basis that explain the relationship between stress and the development of the disease. In our hands, healthy women show elevated levels of β-endorphin, levels that are even higher in postmenopausal women. In women with BC, however, significantly lower levels appear, with no differences between premenopausal and postmenopausal women. These data correlate with cortisol levels, which are much higher in women with BC regardless of their hormonal status. Neoadjuvant chemotherapy treatment only improves β-endorphin levels in postmenopausal women, without recovering the levels of healthy women. In women treated with neoadjuvant chemotherapy, both premenopausal and postmenopausal maintain elevated cortisol levels that are indicative of the stressful situation. Regulation of stress levels by modulation with β-endorphin could be an alternative pharmacological therapy against tumor growth and development, as well as its ability to promote in patients feelings of well-being that improve the development of their disease.