PROGNOSTIC CHARACTERISTICS IN BREAST CANCERS AFTER HORMONE REPLACEMENT THERAPY

We examined the influence of hormone replacement therapy (HRT) on brea st tumour biology by comparing the prognostic characteristics of breas t cancers and survival in 121 women prescribed replacement hormones be fore diagnosis with those in 1468 women without such treatment. The wo men receiving HRT had a lowered relative risk of being diagnosed with tumours of more than 20 mm in diameter, OR = 0.7 (CI 0.5-1.0) and axil lary lymph node dissemination, OR = 0.7 (CI 0.4-1.1). These risk reduc tions were most pronounced and statistically significant in the women who had been prescribed a combined estradiol-progestin regimen. The pa tients in this compound group also had a diminished relative risk of h aving poorly differentiated tumours. Further, there was an indication that the women prescribed HRT, and especially those with conjugated es trogens/estradiols alone, had a decreased relative risk of developing aneuploid tumours. There was no clear pattern for women receiving the biologically weak oestriol, although risk estimates were generally hig her for unfavourable tumours in comparison with those receiving the hi gher potency compounds. Adjustments for indications of earlier detecti on (i.e. lead time bias) did not influence the pattern or magnitude of the risk estimates. No association between any type of HRT and surviv al after breast cancer diagnosis was noted, but analyses were based on ly on 19 breast cancer deaths among exposed patients. We conclude that breast cancers occurring after treatment with HRT, especially the com bined estrogen-progestin regimen, seem to have more favourable tumour features than rumours in non-treated women. Our findings may reflect a less aggressive biological behaviour of breast cancers in women recei ving HRT, or in part be explained by the earlier detection of the tumo urs in these women.