Influence of adjuvant chemotherapy with cyclophosphamide, methotrexate and 5-fluorouracil on plasma melatonin and chosen hormones in breast cancer premenopausal patients

Objective: To investigate the eff ect of chemotherapy on levels of melatonin in patients with breast cancer. Background: In light of reports on the possible oncostatic role of melatonin in breast cancer patients, it is essential to know the influence of adjuvant chemotherapy with cyclophosphamide, methotrexate and 5-fluorouracil (CMF) on plasma melatonin concentration as well as on its contributing factors, e.g. current hormonal state of the organism. The combination therapy is one of the oldest, safest and most commonly prescribed adjuvant treatments. Method: Twenty-four breast cancer patients on CMF chemotherapy were studied along with a control group of 16 healthy pre-menopausal women. Results: Plasma melatonin concentration (determined by RIA method) in breast cancer patients prior to treatment did not differ significantly from that of healthy women, but it was significantly increased after the initial cycle of CMF, and significantly increased as compared to a group of healthy women. We did not notice any significant interactions between plasma melatonin and growth hormone, prolactin, estradiol, progesterone, cortisol and met-enkephalin concentrations in all studied groups. Conclusion: The possible oncostatic action of melatonin warrants further investigation to elucidate whether the induced increase of blood melatonin concentration is essential to successful CMF chemotherapy.