Hormone therapy and estrogen receptor expression in breast cancer

Postmenopausal hormone therapy (HT) may increase breast cancer risk and influence tumor characteristics. We investigated 321 postmenopausal women aged 50-65 years, with breast cancer, diagnosed and treated at Radiumhemmet, Karolinska Hospital, during 1993-1997. In women using HT (n =90) estrogen receptor concentration (ER) at diagnosis were lower than in non-users (n =135) (1.17 vs 1.70 fmol/microg; p <0.05). HT users also had a tendency to less multifocal (5 vs 12%) (p <0.05) and metastatic disease (5% vs 2%) however this was not statistically significant. The estrogen receptor expression is always considered in the judgement on hormone dependency and the clinical decision on adjuvant endocrine therapy. A suppression of ER during HT could tentatively influence the treatment decisions in breast cancer patients and maybe disregard patients from endocrine treatment.