“Know thine enemy” runs the adage, and Fisher’s and Bonadonna’s trials had shown that it was essential to “know” the cancer as intimately as possible before rushing to treat it. The meticulous separation of breast cancer into distinct stages, for instance, was a crucial prerequisite to the success of Bonadonna’s study: early-stage breast cancer could not be treated like late-stage breast cancer. The meticulous separation of ER-positive and ER-negative cancers was crucial to Fisher’s study: if tamoxifen had indiscriminately been tested on ER-negative breast cancer, the drug would have been
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