News

Drug to prevent breast cancer near approval

Scott Gottlieb, New York

A scientific advisory panel of the Food and Drug Administration (FDA) has overwhelmingly voted to recommend the approval of tamoxifen for reducing the incidence of breast cancer in healthy women with an increased risk of developing the disease.

In the carefully worded ruling, which is likely to be followed by the FDA, the panel stopped short of agreeing that the drug could actually prevent breast cancer over the long term, ruling that this has not yet been proved by clinical studies. The panel's deliberations highlighted some of the lingering uncertainty over whether healthy women should use the drug.

Doctors and scientists on the panel are worried that the drug might be used by women with only a slightly increased risk of developing breast cancer who do not understand tamoxifen's considerable risks. These risks include an increased incidence of endometrial cancer, pulmonary emboli, and cataracts. Moreover, the committee could not determine exactly for which high risk women the benefits might be worth the known risks.

The committee's decision to recommend tamoxifen was based in large measure on a US government study that found that women with a high risk of getting breast cancer who received tamoxifen had a lower incidence of developing the disease than similar women who received a placebo (18 April, p 1187). However, a smaller UK trial published in the Lancet appeared to contradict the US study (18 July, p 162).

Some scientists have dismissed the discrepancies found between the two studies as due to the different eligibility criteria. The UK study included women who were younger and had a close family history of breast cancer and a high risk of carrying one of the breast cancer genes. In contrast, women in the US trial were included according to risk as calculated by factors such as early menarche, late menopause, and older age at first childbirth. In addition, the UK study was smaller than the US study, and some scientists have suggested that as a result it failed to see tamoxifen's benefit.

Dr Judy Garber, director of cancer risk and prevention at the Dana-Farber Cancer Institute in Boston and principal investigator on the US study, said that while the UK study does not negate the findings in the US study, it none the less raised a "set of powerful concerns." In particular, women at highest risk of developing breast cancer whose risk was based on their family history may benefit less from tamoxifen's protective effects.

Proponents of the drug believe that for some women, tamoxifen could help prevent, or at least delay, the onset of breast cancer. "Hopefully with any kind of approval will come plenty of caution about the need to discuss the pros and cons," said Dr Eric Wiener, director of the Breast Oncology Center at the Dana-Farber Cancer Institute.