Ovarian ablation in breast cancer, 1896 to 1998: milestones along hierarchy of evidence from case report to Cochrane review

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Abstract
One of the earliest randomised trials of a treatment for cancer was of ovarian ablation for breast cancer. Apart from surgical removal of the tumour, this is the oldest treatment still used in breast cancer. Its use was first reported in the Lancet in 1896,1 but not until the 1940s was it first assessed in randomised trials and it was nearly a century before the Early Breast Cancer Trialists' Collaborative Group provided a reliable estimate of its effect on resectable breast cancer.2 Now, 50 years after its completion, the first randomised trial of ovarian ablation has been included in the first of the collaborative group's overviews to be prepared as a Cochrane review.3 Here I describe this journey along a hierarchy of evidence and show why the research is still relevant. ### Summary points The hierarchy of evidence needed to determine treatment efficacy ranges from case reports, through case series and comparison with historical groups, to randomised trials and systematic reviews Over the past 100 years the investigation of ovarian ablation for women with breast cancer has progressed along this hierarchy The first case report was published in 1896 and the first randomised trial began in 1948 Not until 1992 did a systematic review show this treatment to be clearly effective David Byar described an eight point hierarchy for the quality of evidence needed to determine a treatment's efficacy. This leads from anecdotal case reports, through case series and comparison with historical groups, to randomised trials and systematic reviews.4 Olkin added a ninth point: a meta-analysis in which individual patient data from each relevant trial are collected and analysed.5 He described this as being in the “realms of luxury,” but several examples now exist.6 Occasionally, the evidence that a treatment is effective becomes apparent without needing to …