More potential for breast cancer prevention

In the Journal of the National Cancer Institute a new study shows promise for reducing risk for beats cancer through another osteoporosis drug (Lacroix, Powles et al. 2010). Risk of breast cancer is reduced but the small number of women in the trial does not rule out side effects similar to tamoxifen.

The potential for prevention of breast cancer through drug therapies is supported by results from randomized trials of SERMs (Fisher, Costantino et al. 1998; Cummings, Duong et al. 2002; Martino, Cauley et al. 2004; Vogel 2010; Vogel, Costantino et al. 2010). Both tamoxifen and raloxifene have been shown to reduce the incidence of invasive breast cancer by approximately 50%, with the benefit largely limited to ER+ tumors, where risk is reduced by as much as 80%. Adverse effects of tamoxifen suggest that the potential use for chemoprevention will be limited to a subset of women at increased risk and younger in age, in large part because of increasing incidence of adverse effects with age (Gail, Costantino et al. 1999). The adverse effects experienced in the 8 year randomized trial of raloxifene (Continuing Outcomes Relevant to Evista (CORE)), on the other hand, are somewhat fewer than those observed for tamoxifen (Chen, Rosner et al. 2007). Of note, there was no statistically significant difference in overall mortality or uterine cancer among women randomized to Raloxifene compared to placebo. While Raloxifene is approved in the United States for use to prevent osteoporosis in postmenopausal women (Physicians’ Desk Reference 2005), and a number of cost effectiveness studies support this use in conjunction with screening for osteoporosis (Kanis, Borgstrom et al. 2005; Stevenson, Lloyd Jones et al. 2005; Mobley, Hoerger et al. 2006).

We calculated some numbers to help women decided (Chen, Rosner et al. 2007). Among women in the top 10 percent of breast cancer risk in each 5-year age group we estimated how many women would need to take a SERM for 5 years to prevent one case of breast cancer. Thee numbers are summarized in the table below from Chen, et al., Cancer 2007. Physicians will need to play a key role in advising women in this rapidly evolving field.

Age group	Incidence of breast cancer per 100,000	Number treated for 5 years to prevent 1 case
50-54	504	79
55-59	668	60
60-64	756	53
65-69	921	43

A number of explanations have been proposed for the low use of tamoxifen for preventing breast cancer (Waters, Cronin et al. 2010)(see story) . These include the need for drug (hormone therapy), conerns regarding the adverse effect (increased risk fo endometrial cancer), and other side effects (Waters, Weinstein et al. 2007; Waters, Weinstein et al. 2009)

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