Reversal of clinical resistance to LHRH analogue in metastatic prostate cancer by the pineal hormone melatonin: efficacy of LHRH analogue plus melatonin in patients progressing on LHRH analogue alone.

OBJECTIVE: Experimental and preliminary clinical studies have suggested that the pineal hormone melatonin (MLT) may stimulate hormone receptor expression on both normal and cancer cells. Moreover, MLT has appeared to inhibit the growth of some cancer cell lines, including prostate cancer, either by exerting a direct cytostatic action, or by decreasing the endogenous production of some tumor growth factors, such as prolactin (PRL) and insulin-like growth factor-1 (IGF-1). On this basis, a study was carried out to evaluate the clinical efficacy of a neuroendocrine combination consisting of the LHRH analogue triptorelin plus MLT in metastatic prostate cancer progressing on triptorelin alone.

MATERIAL AND METHODS: The study including 14 consecutive metastatic prostate cancer patients with poor clinical conditions (median age: 70.5 years; median PS: 50%), refractory or resistant to a previous therapy with the LHRH analogue triptorelin alone. Triptorelin was injected i.m. at 3.75 mg every 28 days, and MLT was given orally at 20 mg/day in the evening every day until progression, starting 7 days prior to triptorelin.

RESULTS AND CONCLUSIONS: A decrease in PSA serum levels greater than 50% was obtained in 8/14 (57%) patients. Moreover, PSA mean concentrations significantly decreased on therapy of triptorelin plus MLT. In addition, a normalization of platelet number was obtained in 3/5 patients with persistent thrombocytopenia prior to study. Mean serum levels of both PRL and IGF-1 significantly decreased on therapy. Finally, a survival longer than 1 year was achieved in 9/14 (64%) patients. This preliminary study would suggest that the concomitant administration of the pineal hormone MLT may overcome the clinical resistance to LHRH analogues and improve the clinical conditions in metastatic prostatic cancer patients.