Abstract
BACKGROUND: The benefit of early detection of breast cancer is assumed to be achieved primarily by identifying disease before it has spread beyond the breast. In support of early detection, the survival experience of women with breast cancer decreases as the mean size of the cancer increases. It is not clear if women with regional spread (node-positive breast cancer) benefit from early detection to the same extent that women with node-negative breast cancer do. METHODS: A review was conducted of the survival experience of 1894 patients with invasive breast cancers 5.0 cm or less in size. Cases were divided into node-positive and node-negative, and tumours were categorized by size (0.1-1.0 cm, 1.1-2.0 cm, and 2.1-5.0 cm). After a mean follow-up of 9.9 years, 368 cancer-specific deaths had occurred in the cohort. The effect of tumour size on 15-year survival for subgroups of women with node-positive and node-negative breast cancer was estimated. RESULTS: Tumour size was a strong predictor of 15-year survival in both the node-positive and node-negative cancer subgroups. A decline of 1.0 cm in size was associated with a reduction in 15-year mortality of 10.3% in the node-positive group and of 2.5% in the node-negative group. A decline of approximately 1.5 cm was associated with a reduction in mortality of 23.0% in the node-positive group and of 10.8% in the node-negative group. CONCLUSIONS: The impact of decreasing tumour size on 15-year survival is much greater for women with node-positive than for women with node-negative breast cancers. Contrary to expectation, the benefit of screening is likely to be greater for women with relatively advanced breast cancer than for women with earlystage disease.