RECURRENCE-FREE SURVIVAL IN BREAST-CANCER IMPROVED BY ADJUVANT TAMOXIFEN - ESPECIALLY FOR PROGESTERONE-RECEPTOR POSITIVE TUMORS WITH A HIGHPROLIFERATION

Although the beneficial effect on breast cancer of adjuvant tamoxifen (TAM) is well established, in the series studied by our group this eff ect seems to have been restricted to patients with steroid receptor (e specially progesterone receptor (PgR)) positive tumors. However, as so me patients with PgR-positive tumors manifested recurrence despite adj uvant TAM treatment, the question arose whether some other biological factor(s) could be used to identify these non-responding cases. The le vel of the S-phase fraction (SPF), as measured by flow cytometry, has been shown to be a useful prognostic marker, prognosis being better in cases where the SPF is low than in those where it is high. The aim of the present study was to relate the prognosis after adjuvant TAM to S PF among patients with PgR-positive tumors. In the PgR-positive group as a whole, the effect of TAM on prognosis was more pronounced in the high SPF group than in the low SPF group (p = 0.005) the respective de crease in 3 year recurrence rate was from 19 to 43% and from 17 to 9%. Multivariate analysis of the data for the TAM-treated group showed th e level of PgR concentration (low positive vs, high positive), lymph n ode status, and tumor size to be independent predictive factors, but n ot the level of SPF (i.e. high vs. low). By contrast, among patients n ot treated with TAM, the SPF was a strong independent prognostic facto r. To sum up, SPF was a strong independent predictor of outcome only f or patients receiving no systemic adjuvant therapy, but not in patient s receiving adjuvant TAM. Patients with PgR-positive and high S-phase tumors derived more benefit from TAM than patients with PgR-positive a nd low SPF tumors.