Disease-free interval and estrogen receptor activity in tumor tissue of patients with primary breast cancer: analysis after long-term follow-up.

Specific estrogen receptor activity (ER) was found in 115 of 175 (66%) tumors of patients treated for primary breast cancer in the period 1974-1981; 60 patients had ER-negative tumors. All patients were under observation for at least 48 months (median 76 months). The 24 patients who received adjuvant chemotherapy as part of their initial treatment, were excluded from the analysis of the disease-free interval (DFI). Groups of patients with ER-positive or ER-negative tumors did not differ significantly in clinical characteristics. Patients with ER-positive tumors had a significantly longer DFI than those with ER-negative tumors only in the first year after initial treatment. After prolonged observation a significant difference in recurrence rates was no longer found. In premenopausal women, the DFI was not different for those with ER-positive compared to those with ER-negative tumors, not even in the first year of observation. However, in postmenopausal women, those with ER-positive tumors had a significantly longer DFI up to 3 years after initial treatment but not thereafter. There was no difference in DFI between the ER-positive and ER-negative groups when the tumor stage was taken into account. It is concluded that the ER status of the primary tumor affects prognosis only on the short term.