Journal of the Royal Society of New Zealand abstracts

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The seasonal variation in breast cancer detection: its significance and possible mechanisms

Barbara H. Mason, Ian M. Holdaway*

We have demonstrated a number of temporal patterns in subjects with breast cancer including (a) an annual rhythm in the month of first sign or symptom of breast cancer (b) an increased frequency of tumour recurrence one year from diagnosis, and (c) abnormal annual and daily hormonal rhythms in breast cancer patients. Increased detection of breast cancer in spring-summer appears to be influenced by hormonal parameters, as it was more pronounced in premenopausal women with progesterone receptor (PR) positive tumours. Also, oestrogen receptor (ER) positive and PR negative primary tumours recurred significantly more frequently in the same season that their primary cancer was initially detected. Women who initially detected their breast cancer in spring/summer had a significantly longer survival than those detecting their tumour at other times of the year, especially postmenopausal women with ER+ve and PR+ve tumours. Season of tumour detection also appeared to influence the predictive value of a number of prognostic factors for breast cancer, including ER and PR status, parity, lactational history and body mass index. Several possible mechanisms for seasonal effects in breast cancer were investigated. There was a significant circannual variation in the mean monthly PR concentration in parallel with changes in detection, with peak PR levels in April and nadir values in August/September. Women with previous breast cancer also showed an abnormal melatonin rhythm, with a paradoxical reduction of serum melatonin in wintertime in those who were winter detectors of breast cancer. Serum oestradiol levels measured in summertime were significantly higher in summer detectors than winter detectors of breast cancer. Serum insulin-like growth factor-I (IGF-I) did not increase in summer in breast cancer cases as it did in controls. There was no increase in cortisol production in winter in breast cancer cases, but there was in control women; the normal nocturnal TSH peak was reduced in breast cancer cases compared with controls. Women with breast cancer thus have blunted seasonal hormone changes which may contribute to their tumour growth patterns. Unravelling the hormonal interactions between tumour and host in breast cancer patients will have to take into account daily, annual, and monthly rhythms in hormonal parameters.

Keywords: chronobiology, breast cancer, human

(c) Journal of The Royal Society of New Zealand,

Volume 24, Number 4, December 1994, pp 439-449

PDF file of entire paper: medium quality (697K); (scanned from paper original: notes about this process)

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