Aberrant nocturnal cortisol and disease progression in women with breast cancer

While a relationship between disruption of circadian rhythms and the progression of cancer has been hypothesized in field and epidemiologic studies, it has never been unequivocally demonstrated. We determined the circadian rhythm of cortisol and sleep in women with advanced breast cancer (ABC) under the conditions necessary to allow for the precise measurement of these variables. Women with ABC (n = 97) and age-matched controls (n = 24) took part in a 24-h intensive physiological monitoring study involving polysomnographic sleep measures and high-density plasma sampling. Sleep was scored using both standard clinical metrics and power spectral analysis. Three-harmonic regression analysis and functional data analysis were used to assess the 24-h and sleep-associated patterns of plasma cortisol, respectively. The circadian pattern of plasma cortisol as described by its timing, timing relative to sleep, or amplitude was indistinguishable between women with ABC and age-matched controls (p's > 0.11, t-tests). There was, however, an aberrant spike of cortisol during the sleep of a subset of women, during which there was an eightfold increase in the amount of objectively measured wake time (p