A method for making estimates of the benefit of the late use of letrozole in patients completing 5 years of tamoxifen.

This article discusses the rationale for 2 methods of making estimates of the benefit of letrozole as extended adjuvant hormonal therapy after 5 years of tamoxifen. It uses information from the Overview metaanalyses to develop general rules for making estimates of remaining risk of relapse for women completing 5 years of adjuvant tamoxifen without relapse. The first derived method shows that the expected benefit for such a woman is approximately one tenth of her risk of relapse in years 0-10 if untreated. The second method uses a modification of Adjuvant!, a decision support tool, and makes similar estimates. The decision tool supplies needed estimates of initial risk and allows adjustment for competing mortality. Uncertainties involved in making these estimates are also discussed.