Evaluation of central serotonin sensitivity in breast cancer survivors with cancer-related fatigue syndrome

Context: Increased central serotonin sensitivity is hypothesized to contribute toward the development of cancer-related fatigue syndrome (CRFS).

Objectives: To compare the responses of breast cancer survivors with or without CRFS to the buspirone challenge test (an index of central serotonin sensitivity).

Methods: Disease-free women who had successfully completed treatment for early-stage breast cancer were assessed. On the basis of the diagnostic interview for CRFS and a structured psychiatric interview, women were classified as either "cases" of CRFS or "controls." Women with comorbid psychiatric diagnoses were excluded. Volunteers underwent a challenge test using buspirone (a serotonin-selective agonist) using a double-blind, randomized, placebo-controlled protocol. Cortisol and prolactin responses were assessed at hourly intervals for the four hours after administration of buspirone.

Results: Fourteen cases of CRFS and 28 controls participated in the study. There were no significant differences in baseline or stimulated cortisol release after buspirone challenge. There were differences neither in basal prolactin levels in the two groups nor in the total prolactin response to buspirone (as measured using the area under the curve). In patients with CRFS, peak prolactin response occurred at 120 minutes and sustained until 180 minutes post buspirone. In controls, peak prolactin response occurred at 60 minutes and then began to decline.

Conclusions: This study has demonstrated the utility and acceptability of buspirone as a probe of central serotonin sensitivity in this population. No evidence was found for alterations in central serotonin sensitivity in patients with CRFS. Conclusions are tentative, however, because poor recruitment resulted in a small sample and an underpowered comparison.