This article presents the preliminary results from STAR, a large clinical trial comparing tamoxifen and raloxifene in postmenopausal women at increased risk of breast cancer. The study found comparable reduction in breast cancer risk. While the article reported that for the women taking raloxifene, the incidence of uterine cancer, blood clots, and cataracts were less than the women taking tamoxifen, only the difference in cataract was statically significant. This oversight is major as the incidence of uterine cancer and blood clots may be among the factors a woman considers when deciding which, if either breast cancer risk treatment option, is right for her. The other big omission is that the comparability in breast cancer reduction is only for invasive breast cancer; tamoxifen reduced the risk of less aggressive breast cancer (i.e. ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS) while raloxifene did not. If the risks for all breast cancer events had been compared, the reported outcome of the study may have differed.
No mention of the costs of either tamoxifen or raloxifene was made.
Failure to mention the lack of statistical significance for the incidence of uterine cancers and blood clots for women at increased risk of breast cancer taking raloxifene as compared with those taking tamoxifen is an important lack of framework. The story didn’t describe how well either drug prevents breast cancer (i.e. how many would have developed it and how many were prevented from developing it because of treatment. In addition, the reported impact on the quality of life was the same for the two treatments.
The increased incidence of other, less-invasive forms of breast cancer (ductal carcinoma in situ and lobular carcinoma in situ) was not mentioned. The absolute number of cases for the side effects was not presented.
The article discussed some recently released data from a large clinical trial comparing tamoxifen and raloxifene in postmenopausal women considered to be at increased risk of breast cancer. Though the study found that the reduction in invasive breast cancer was the same for the two drugs, the article failed to distinguish between differences in side effects that were and were not statistically significant (i.e. that there were 36% fewer uterine cancers and 29% fewer blood clots among women who took raloxifene were not statistically significant while the 21% fewer cataracts were statistically significant). As the purported benefit of raloxifene over tamoxifen is about the prevalence of side effects, this distinction is important.
While it was noted within the story that the average five-year breast cancer risk for the women in the study was 3.4%, the overall tone of the article was one of disease mongering. One quoted expert (chairman for one of the studies) is quoted as saying that as many as 10 million postmenopausal women are at increased risk for breast cancer. Failure to present the absolute number of breast cancer cases and side effect cases in each study group serves to amplify concern about cancer risk.
The results of this study , its analysis, and interpretation have not yet been peer reviewed or published. Two quotes, one from the executive director of Breast Cancer Action and a spokesperson from the American Cancer Society, contribute valuable cautionary interpretation for the rest of the material presented in the article.
The article mentioned tamoxifen, the only medication to date that has been approved by the FDA for reducing breast cancer risk in healthy women. However the article failed to mention that not doing anything, increased screening (such as more frequent mammograms, screening with MRI, ductal lavage) and prophylactic mastectomy are also options to decrease breast cancer risk.
Although the article mentions that doctors could prescribe raloxifene for the purpose of reducing breast cancer risk, it is not yet approved by the FDA for this purpose and would therefore represent an off-label use of this medication.
The use of raloxifene as a medication to reduce breast cancer risk is new.
We can’t be sure if the story relied solely or largely on a news release, although the story does appear to rely on information in the STAR study press release.