The National cancer institute in April announced that raloxifene is equal in efficiency to tamoxifen in prevention of breast cancer with lesser side effects. However the final results of this study challenges the view presented by scientists from the national cancer institute.

In the press conference scientists from the National cancer institute said that raloxifene is clearly superior to tamoxifen in prevention of breast cancer because of lesser incidence of side effects. They claimed that raloxifene users had 36 percent fewer uterine cancers and 29 percent fewer blood clots, making it a safer choice.

However the final results of the study published show that the incidence of uterus cancer was not statistically different between the two groups. Also some scientists think that the incidence of blood clots in the study were so low to draw any meaningful conclusion.

The release of the details of the study at the annual meeting of the American society of clinical oncology has created a heated debate among experts. A number of think that the study should have been first presented at this meeting rather than making the details known in a hasty fashion at a news conference. Presenting such important studies at meetings like American society of clinical oncology, provide great opportunity for peer review.

Dr. Leslie Ford, who is National cancer institute's prevention chief, defended her characterization of raloxifene as a clear winner and the way the news came out. She said the press conference was called to give women in the study the first word of its results without them "leaking out" as happened with two earlier high-profile women's health studies.

Other experts questioned the urgency, because these drugs are taken for five years to prevent long-term breast cancer risks, a very different situation from a drug to treat a disease that could have an immediate life-or-death impact.

The study in question evaluated efficiency of raloxifene in breast cancer prevention in comparison to tamoxifen. About 20,000 postmenopausal women at high risk of breast cancer because of gene mutations, family history or other reasons took part in the study. The study to be published in a forthcoming issue of the Journal of American Medical Association. The results showed the following:

Incidence of invasive breast cancer: 168 among the 9,745 raloxifene users; 163 among the 9,726 who took tamoxifen.

Uterine cancers: 36 among the 4,732 on tamoxifen; 23 in the 4,712 on raloxifene.

Less serious forms of breast cancer developed in 57 women on tamoxifen and 80 on raloxifene.

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