A psychoneuroendocrine study of brain dopaminergic sensitivity in locally limited or metastatic cancer patients.

In addition to the occurrence of pain, the evidence of a diminished capacity to feel pleasure is one of the most common cancer-related symptoms. Recent advances in psychoneuroendocrinological knowledge has shown that the perception of pleasure is mainly mediated by the dopaminergic pathways in the brain. Moreover, it has also been demonstrated that the brain dopaminergic sensitivity may be clinically explored by evaluating the endocrine response to the administration of dopaminergic agents, such as apomorphine, which consists of a decline in PRL concentrations and an increase in GH and cortisol levels. The present study was performed to evaluate dopaminergic sensitivity by the administration of apomorphine in cancer patients in an attempt to document possible cancer-related neuroendocrine anomalies, which could explain the psychological status of the patients. The study included 24 cancer patients (breast cancer: 12; colorectal cancer: 7; non-small cell lung cancer: 5), 12 of whom showed distant organ metastases. Apomorphine was given orally at 0.01 mg/kg b.w., by collecting venous blood samples before and after 20 and 60 minutes. A normal decline in PRL levels was seen in both non-metastatic and metastatic cancer patients. No cortisol increase in response to apomorphine was achieved and the lack of cortisol response was particularly evident in metastatic patients. No GH rise occurred in either metastatic or non-metastatic cancer patients. Finally, no significant difference in the endocrine response to apomorphine was seen in relation to the histotype of tumor. The results of this study show that the neoplastic disease is characterized by neurochemical alterations involving pleasure-related dopaminergic pathways, which are more evident in the metastatic disease, without particular differences in relation to tumor histotype. Therefore, the psychological condition of cancer patients would not depend only on psychological factors, but it could be due at least in part to cancer-related neuroendocrine alterations involving the dopaminergic system.