A case-control study of hormone replacement therapy after primary surgical breast cancer treatment

To investigate the presumed influence of hormone replacement therapy (HRT) on the progression of and death due to breast cancer.

In order to make a detailed analysis, we selected a group of 21 patients with the diagnosis of invasive breast cancer who had HRT after primary surgical treatment. Each patient from the selected group was compared with two patients from the control group with the diagnosis of invasive breast cancer who did not have HRT after primary surgical treatment. The control cases were matched to selected HRT patients with regard to age at time of the diagnosis, year of diagnosis, diameter of the tumour, metastatic spread in the axillary lymph nodes, and disease-free interval until applying HRT. The same criteria were applied in all analyses. The data were analysed by odds ratio (OR) calculation with a confidence interval of 95%, taking into account residual malignancy and death due to breast cancer in both groups (including carcinoma in the contralateral breast).

HRT was applied in 21 patients treated for breast cancer. In 33% of them, radical mastectomy revealed metastases in the axillary lymph nodes. Hormone receptors could not be found in 57% of patients. In the majority of patients the tumour measured 17.6mm in diameter. HRT was started on average 62 months (range 1-180 months) after diagnosis, and lasted an average of 28 months (range 3 72 months). All 21 patients used oestradiol as HRT, i.e. a non-conjugated oestrogen. Combined hormonal therapy (oestrogens + progestagens) was given to 95% of patients with median age of 47 years (range 41-59 years) at the beginning of HRT. Relapse was observed in four patients (19%) of the HRT group; of these, one had a carcinoma of the contralateral breast. In the control group, relapse was observed in five patients (11%); one of these five patients had a carcinoma of the contralateral breast. In the HRT group, there were no deaths among the patients with confirmed relapse, while one patient died in the control group. The estimated risk (OR= 1.74, 95%S CI 0.34-8.88) of relapse of breast cancer was calculated by comparing data from HRT users, who had received HRT for 28 months (range 3-72 months) on average, with data from the control group. The estimated risk of breast cancer relapse in HRT users who had been receiving HRT for less than 24 months was 0.65 (OR = 0.65, 95% CI 0.02-7.85).

Despite the inherent limitations of retrospective data and the need for prospective randomized trials to assess the possible influence of HRT on progression after breast cancer treatment, the present observations suggest that HRT treatment for less than 24 months does not appear to have a pronounced adverse effect on cancer outcome. Nevertheless, until appropriate clinical trials determine that HRT is safe, caution is needed.