532 Background: The value of 5 years of Tam in premenopausal women with breast cancer and its benefit according to endocrine responsiveness of the tumor has not been completely defined.
METHODS
Between 1993 and 1999, IBCSG Trial 13-93 enrolled 1246 (planned sample size, 1225) premenopausal women with N+, early stage breast cancer. All patients (pts) received chemotherapy (ACx4 cycles followed by immediate or delayed classical CMFx3 cycles) to be followed by Tam (20 mg daily) for 5 years or no hormonal therapy. The primary endpoint was disease-free survival (DFS). Estrogen receptor (ER) content was determined locally by immunohistochemistry (IHC) for 56% of pts and ligand-binding assay (LBA) for 44%. Tumors were classified as ER-absent if IHC expression=none or LBA=0 fmol/mg cytosol protein; ER-low if IHC=negative or borderline or LBA=1-9 fmol/mg cytosol protein; and ER-positive otherwise.
RESULTS
735 (59%) pts had ER-positive disease. 61% had 1-3 N+, 42% had tumors ≤ 2 cm, 11% had grade 1 and 40% had grade 2 tumors, and the median age was 44 years. Tam provided significantly longer DFS compared with no Tam for the pts with ER-positive tumors. Pts with ER-low tumors obtained an intermediate benefit from Tam and pts with ER-absent tumors may have experienced a detrimental effect of Tam. The test for trend was significant (p=0.002).
CONCLUSIONS
Tam significantly improved prognosis in premenopausal patients with endocrine responsive disease. It should not be considered as adjuvant therapy in patients with ER-absent tumors. [Figure: see text] No significant financial relationships to disclose.