Significance of S-phase fraction and hormone receptor content in the management of young breast cancer patients.

Tumours from 336 breast cancer patients under the age of 50 were analysed for hormone receptor content and by DNA flow cytometry. Sixty-six percent of the tumours were positive for estrogen receptors (ER), 60% were progesterone receptor (PR) positive and 42% showed DNA diploid profiles. DNA hypodiploid tumours were relatively frequent (7%), especially in patients aged 40 years or less (11%). S-phase fraction (SPF), with a mean of 10%, correlated significantly with receptor status, DNA ploidy, lymph node status, tumour size and age. With a median follow-up period of 34 months, the distant recurrence-free interval was independently predicted by lymph node status, tumour size, SPF and PR content. Amongst the 212 patients who had not received adjuvant systemic treatment, receptor status was, in addition to lymph node status and SPF, independently related to distant recurrence rate. A high SPF identified a subgroup with high recurrence rate, comprising approximately one third of the node-negative patients. Similarly, the one third of node-positive patients who had PR-positive tumours with a low S-phase fraction formed a subgroup with low recurrence rate. We conclude that hormone receptor assays and DNA flow cytometry should be useful tools in the management of breast cancer patients less than 50 years of age.