A seasonal variation in breast cancer

To demonstrate a seasonal variation in the detection of breast cancer in women diagnosed at St Marks Breast Centre, Auckland.

Data on women diagnosed with breast cancer at St Marks Breast Centre from January 1992 till December 2001 were obtained from the computerised database.

A total of 1760 women were diagnosed with breast cancer; 1584 were referred by their general practitioner and 176 self referred. The peak incidence of seasonal diagnosis was in spring (September, October, November) with 521 cases. The lowest incidence was in summer (December, January, February) with 375 cases. These findings were consistent annually from 1992 to 2001.

There is a seasonal variation in the incidence of breast cancer similar to that noted in other studies. Our findings suggest that temporal factors and possible behavioural patterns may have a role in this seasonal variation.