Relationship between age at diagnosis and outcome of premenopausal breast cancer: age less than 35 years is a reasonable cut-off for defining young age-onset breast cancer

Previous studies have reported significantly worse outcomes in younger women with breast cancer. The cut-off for young age differed between studies and it is unclear whether the survival-age relationship is a linear function across age in premenopausal women. We analyzed data on 9,885 breast cancer patients aged ≤50 years who entered the Korean Breast Cancer Society Registration Program between 1992 and 2001. Overall survival data were compared among age groups. The median follow-up duration was 74.4 months. Of all patients, 351 were aged