Weighing the risks and benefits of tamoxifen

My colleagues and I have shown how to compare the risks and benefits of tamoxifen by combining 3 ingredients:¹ the absolute risks of breast cancer and other endpoints, such as stroke, in the absence of tamoxifen; the effects of tamoxifen on these background risks (from data in Fisher and associates²); and weights for comparing the various outcomes. We used weights of 1.0 for life-threatening outcomes (invasive breast cancer, stroke, pulmonary embolism, hip fracture and endometrial cancer), 0.5 for severe outcomes (in situ breast cancer, deep vein thrombosis) and 0 for other events. We pointed out, however, that a woman's own preferred weights could be used. Tables 10 to 12 in Gail and colleagues¹ indicate that the risks of tamoxifen outweigh the benefits in many women, especially older women in whom the risks from stroke and endometrial cancer are appreciable. Indeed, Rockhill and collaborators³ estimated that only 2.3% of women in the Nurses' Health Study would experience a net benefit, according to Tables 10 and 11 in our study.¹ These observations reinforce the warnings outlined by Eric Wooltorton.⁴

Greiver suggests that the findings of Gail and colleagues¹ be incorporated into a computer-based tool. Until such a program, properly validated, is available, Tables 10 to 12 in that article provide useful indications of net risk or benefit.¹