Samuel Shapiro, M.D., from the University of Cape Town Medical School in South Africa, and colleagues evaluated reported trends in the incidence of breast cancer using data from multiple previously published studies. Generally accepted causal criteria were used for the evaluation.

The researchers found that evidence suggesting a correlated decline in the incidence of breast cancer following a decline in the use of HRT has not adequately satisfied the criteria of time order, detection bias, confounding, statistical stability and strength of association, internal consistency, and external consistency. Assessment of biological plausibility was difficult.

"Based on the observed trends in the incidence of breast cancer following the decline in HRT use, the ecological evidence is too limited either to support or refute the possibility that HRT causes breast cancer," the authors write.

Several authors disclosed consulting ties to manufacturers of products discussed in this article.

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