Results of two or five years of adjuvant tamoxifen correlated to steroid receptor and S-phase levels

A Swedish cooperative trial demonstrated that 5 years of adjuvant tamoxifen was more beneficial than 2 years of tamoxifen in the treatment of postmeno pausal women with estrogen receptor (ER) positive, early stage, invasive br east cancer. The main aim of the present study was to investigate the impor tance of progesterone receptor (PgR) and ER concentration levels for patien ts participating in the trial and still distant recurrence free two years a fter the primary operation. Subgroup analyses revealed that only patients w ith ER positive and PgR positive breast cancer had improved distant recurre nce free survival (DRFS) by prolonged tamoxifen therapy .. . 0.0016.. Patie nts with ER negative and PgR negative as well as ER positive and PgR negati ve tumors showed no significant effect of prolonged tamoxifen (. . 0.53 and . . 0.80, respectively). The percentage of ER negative and PgR positive br east cancers was too small (2.2%) for any meaningful subgroup analysis. The re was a significant positive trend that the concentration level of PgR (hi gh positive vs. low positive vs. negative) decreased the recurrence rate fo r those with prolonged therapy. No corresponding pattern was found for the ER content. S-phase fraction did not correlate to the recurrence rate of Pg R positive breast cancers. Patients recurring during tamoxifen therapy had receptor negative tumors to a greater extent than those recurring after tam oxifen treatment. In conclusion, prolonged tamoxifen therapy for 5 years instead of 2 years w as found to be beneficial for patients with ER positive and PgR positive br east cancer, whereas three extra years of tamoxifen had little or no effect for patients with ER positive but PgR negative tumors as well as for stero id receptor negative patients.