Summary Endogenous opioid peptides have been shown to be involved in the regulation of tumour growth. At present, however, no data are available about the secretion of opioid peptides in cancer patients.To draw some preliminary conclusions on opioid brain function in human neoplasms, we evaluated hypophyseal hormone responses to the administration of a met-enkephalin analogue, There is mounting evidence indicating that endogenous opiates play a critical part in the control of immune functions (Weber & Pert, 1984). Moreover, recent experimental observations seem to demonstrate an involvement of endogenous opioid peptides in the regulation of tumour growth. As regards this hypothesis, however, the results are contradictory, since opioid substances have been seen to exert either a stimulatory (Lewis et al., 1983a, b; Simon et al., 1984) or an inhibitory role (Plotnikoff & Miller, 1983) on tumour growth, depending on the different experimental conditions. Opioid antagonists may also have stimulatory and inhibitory effects, depending on the dosage (Zagon & McLaughlin, 1983).As far as the evaluation of endogenous opioid secretion in cancer patients is concerned, no data are yet available. Preliminary results would seem to suggest an anomalous fJ-endorphin circadian rhythm in human neoplasms (Lissoni et al., 1986), the clinical significance of which remains to be determined.To further elucidate the nature of the opioid activity in human cancer, we studied the effects of a met-enkephalin analogue on the release of hypophyseal hormones in a group of patients suffering from early or advanced neoplastic disease.
Materials and methodsThe study was carried out on 14 patients of both sexes (5 men, 4 premenopausal and 5 postmenopausal women), aged between 32 and 53 years (mean age 46.4 years), with histologically proven neoplastic disease. Patients were followed in the outpatient clinic of San Gerardo Hospital, Monza. Diagnosis of cancer was made for at least 4 months prior to study (4 months-5 years; mean 3.8 years). Breast cancer and lung carcinoma were the two neoplasms most frequently represented in our cases. Chronic pain was present in 2 patients only. Clinical data of cancer patients are given in Table I As controls, 12 healthy volunteers (6 men, 4 premenopausal and 2 postmenopausal women) of same age (28-51 yrs; mean 42.4) were included in the study. Volunteers were from among hospital attendants. Moreover, a second group, consisting of 7 patients (4 men, 2 premenopausal and one postmenopausal women), aged between 31 and 58 years (mean 49.3), affected by a chronic medical illness other than cancer, was evaluated. None of the patients was hospitalized during the study. The experimental protocol was explained to patients and volunteers, and informed consent was obtained.None of the cancer patients had been previously treated with oestrogens, antioestrogens or glucocorticoids. No antiemetics or other psychotropic drugs were given for at least one week prior to study. Moreover, no patient received opiates to relieve pai...