S-phase fractions of breast cancer predict overall and post-relapse survival

We studied the correlation of S-phase fraction (SPF) with clinical outcome in 127 pre- or perimenopausal patients with breast cancers treated by neoadjuvant chemotherapy from October 1986 to June 1990. When the patients were analysed using the median value of the SPF as a threshold, there was a small but non-significant difference in favour of low SPF tumours for metastasis-free survival. SPF was the only parameter predicting overall survival in multivariate analysis (P < 0.002) which included T, N, histopathological grade and steroid hormone receptors. The results of metastasis-free survival contrasted with previous analyses with shorter follow-up, so we tested the time-dependent influence of SPF on prognosis. It was thus shown that SPF significantly predicts metastasis-free survival only during the first 30 months, whereas the relative risk of cancer-related death according to SPF remains significant for 56 months. In order to find an explanation for the difference in predictivity between metastasis-free survival and overall survival, we studied the post-relapse survival. Significantly shorter survival (median 12 months) was associated with tumours presenting pre-treatment high SPF values, compared to the low SPF group for which 60% of the patients were still alive after 30 months of metastasis phase (P = 0.002). Our current results, in a homogeneous series with a median follow-up of over 5 years, emphasise the importance of proliferation-related parameters for breast cancer management.