Abstract
Background: Node-negative breast cancers from 2 cm to 5 cm in size are classified as stage ii, and smaller cancers, as stage i. We sought to determine if the prognosis of women with a breast cancer exactly 2 cm in size more closely resembles that of women with a stage i or a stage ii breast cancer. Methods: Using a cohort of 4265 young women with breast cancer, we compared the 10-year breast cancer mortality rates for women who had a tumour 0.1–1.9 cm, exactly 2.0 cm, and 2.1–2.9 cm. Results: In the first 3 years after diagnosis, the survival pattern of women with a 2.0-cm breast cancer was nearly identical to that of women with a larger cancer (2.1–3.0 cm). From year 3 to year 10, the relative survival of women with a 2.0-cm breast cancer was improved and nearly identical to that of women with a smaller cancer. The 10-year survival rate was 89.3% for women with tumours less than 20 mm, 86.1% for women with tumours equal to 20 mm, and 81.2% for women with 21-mm to 29-mm tumours. Conclusions: For young women with small breast cancers, the relative mortality from breast cancer is dynamic with increasing tumour size and varies with time from diagnosis.