Age of diagnosis, tumor size, and survival after breast cancer: implications for mammographic screening.

If mammographic screening is to be recommended to women aged <50, it is necessary that mammographic screening leads to the detection of small cancers and that the survival rate of young women with small cancers is superior to that of women with larger cancers. We reviewed the survival experience of 2,173 patients with invasive breast cancer. There were 392 cancer-specific deaths in the cohort after a mean of 8.9 years of follow-up. We estimated the effects of young age (age <50) of tumor size (in cm) and of mammogram detected (vs. palpable) on breast cancer survival in the cohort. Young age, tumor size >2 cm and tumor palpability were strong and independent predictors of breast cancer mortality in the cohort. The 10-year survival rate for young women with small mammogram-detected breast cancers (<1 cm) was 94%, compared to 86% for women with palpable cancers in the same size group (P < 0.01). Women with a small non-palpable breast cancer that is diagnosed through a mammogram experience very good survival, compared to women with a palpable breast cancer of similar size. Our findings suggest that mammography preferentially detects cancers with good prognosis and calls into question the assumption that detecting breast cancers when they are small by mammography will impact upon mortality from breast cancer.