Chronobiological changes have been detected in various physiological functions of patients with breast cancer, suggesting dysregulation in the pineal gland and melatonin secretion. This study aimed to assess and measure serum melatonin levels pre- and postoperatively in patients who had been diagnosed for the first time with breast cancer.
A sample of first-time breast cancer patients, consisting of 45 women aged 25-65 years, was evaluated and psychometric assessment was completed using the Beck Depression Inventory (BDI), Insomnia Severity Index (White, Weinberg et al) and the Epworth Sleepiness Scale (Cardoso, Spence et al). The Morningness-Eveningness questionnaire (MEQ) was used to assess the chronotype. Serum melatonin levels were measured by radioimmunoassay.
Morning and moderately morning chronotypes were prevalent among the sample (25%, 45.8%, respectively). The finding of a mean BDI score of 13.5±11.2 indicated that depressive symptoms were prevalent among the sample. Despite the finding that a mean of the participants apparently had no symptoms of daytime sleepiness (the mean and standard deviations of the ESS were 7.5±4.4), scores on the ISI (a mean of 16.7±SD 7.3) indicated that insomnia symptoms were prevalent in the sample. Melatonin levels showed an inverse relationship with insomnia severity as measured by the ISI and depression severity, as assessed by the BDI. The postoperative melatonin levels were higher than the preoperative levels. Additionally, the psychometric profile differed among various pathological types of breast cancer according to their hormone receptor profile.
Serum melatonin levels correlated significantly with self-reported sleep quality and psychometric profiles of depression in the present sample of breast cancer patients. The melatonin assay, which is relatively easy to carry out, provided a convenient, objective measure of an important biological correlate of sleep quality and depression. This assay thus represented a confirmatory alternative to the self-report instruments, which may sometimes be unreliable. Future studies should further evaluate the utility of melatonin measures in psychiatric and sleep complaints of breast cancer patients.

© 2020 Zaki et al.