Influence of height, weight, and obesity on breast cancer incidence and recurrence in Auckland, New Zealand.

The relationship between obesity and breast cancer has been investigated in 1281 Auckland breast cancer patients. Using a definition of obesity as a Body Mass Index (BMI) of greater than or equal to 28 kg/m2, 179 (14%) breast cancer patients were classified as obese. The heights, weights, and BMI of 822 breast cancer patients aged 35-64 compared to 518 randomly selected Auckland women of similar age showed no significant difference. Within the breast cancer patients, there was no variation in nodal status or estrogen and progesterone receptor status between obese and non-obese women. However, tumours greater than 5 cm occurred significantly more often in obese patients. Time to recurrence was reduced in obese women with tumours less than or equal to 5 cm, no tumour in the axillary nodes, positive estrogen or progesterone receptor, and without metastases at the time of presentation of the disease. Although obesity has not been shown to influence breast cancer incidence, an effect on tumour recurrence is seen in patients with less advanced disease. This is similar to other reports which suggest that obesity is a weak but positive risk factor for recurrence.