O031 Nocturnal melatonin secretion in post-treatment breast cancer patients: a preliminary study

PURPOSE: Breast-cancer patients frequently report of poor sleep-quality. Although the pathophysiology is unclear, circadian-sleep misalignment is a plausible mechanism. We compared nocturnal melatonin-secretion, a circadian rhythm marker, in post-menopausal, post-treatment (≥12-months) female breast-cancer patients (BCG), with post-menopausal female controls with no history of cancer (CG) METHODS: We recruited 6 BCG and 10 CG from Westmead Hospital breast-cancer outpatient clinic or hospital-staff community, respectively. Participants completed the Pittsburgh Sleep Quality Index (PSQI; >5 PSQI-score=poor sleep-quality) and ~7 days of home-actigraphy (Philips Actiwatch-2, Philips Respironics, USA) to ascertain habitual bed-time (HBT). Later, participants completed an overnight, in-laboratory study, with saliva sampled (n=13) at regular intervals under strict dim-light conditions (<1 lux). Salivary-melatonin concentrations were quantified via radioimmunoassay (University of Adelaide). We measured 1) clock-time when salivary-melatonin concentrations reached 4pg/mL (melatonin onset-[DLMO-4pg/ml]) and 2) time-interval between HBT and DLMO-4pg/ml (indicates circadian-sleep misalignment-[PAR-DLMO]). Data were expressed as median [interquartile range], and compared using 2-sided Mann Whitney U-tests. p<0.05 was considered significant. RESULTS: BCG and CG had similar ages (62.5 [59.5–67.3] vs. 58.5 [54.0–66.3] yrs, respectively; p=0.23). Compared with CG, BCG had higher PSQI-scores (8.50 [5.25–10.75] vs. 4.00 [3.75–5.50] a.u.; p=0.07), but similar HBT (22:49 [21:46-23:38] vs. 22:17 [21:59-22:21] h:min; p=0.26). BCG had later DLMO-4pg/ml (20:46 [20:01-22:03] vs. 18:23 [17:55-20:07] h:min; p=0.03) and shorter PAR-DLMO (1.43 [0.96–2.38] vs. 3.63 [2.18–3.90] hrs; p=0.09), than CG. CONCLUSION: Preliminary data indicate BCG had poorer sleep-quality, delayed melatonin onset, and altered circadian-sleep alignment; compared with CG. We speculate disrupted nocturnal melatonin-secretion potentially influences poor sleep-quality reported by breast-cancer patients.