In reply: Hormone replacement therapy after a diagnosis of breast cancer: cancer recurrence and mortality

In reply: We feel that Hayes and colleagues repeat the editorial comments of Dixon1 that accompanied our article.2

Our investigation, being retrospective, had biases and limitations normally associated with that type of study. In the third and fourth paragraphs of the discussion section of our article, we examined further the sources of bias and their impact.

Hayes and colleagues state that the omission of tumour grade and receptor status from our analysis is a flaw. We agree that including these variables would have made our study more complete, even if we doubt that this would have altered the conclusions. So many of these data were missing that statistical analysis would have been unreliable. As was stated in the methods section, the analysis was adjusted for the covariate HRT use before diagnosis. Tamoxifen use was very similar among HRT users and non-users (58% and 60%, respectively), and any bias introduced by this difference would be insignificant.

The scope of our article, as suggested by its title, was limited to the issue of cancer recurrence and mortality. We did not specifically investigate the impact of HRT on cardiovascular and thromboembolic events. Nonetheless, if car-diovascular disease had increased mortality, this would have been apparent as an increase in all-cause mortality.

We agree with Hayes and colleagues that it is vital that the media interpret studies correctly for the general public. We are disappointed that Hayes and colleagues have misinterpreted our conclusion. Our article does not advocate HRT use by women with breast cancer.

We explicitly stated that "These results need to be confirmed in a randomised trial before HRT can be advocated for all women who have had breast cancer." Furthermore, ". . . the observed association between HRT use and [reduced] risks of breast cancer recurrence and death cannot be inferred to be causal".

We believe that we are justified in our conclusion that HRT use in women diagnosed with breast cancer is not associated with an increased risk of recurrence of breast cancer or a shortened life span. It is our clinical practice to use HRT only when alternative therapy fails.