Long term, tamoxifen stops more cancer than Evista

* Tamoxifen about 24 pct more effective preventing cancer

* Raloxifene still has far fewer side effects

* Death rates similar for women taking either drug
(Rewrites first paragraph, adds details and background)

By Maggie Fox, Health and Science Editor

WASHINGTON, April 19 (BestGrowthStock) – Longer-term results from a
head-to-head trial of two drugs that prevent breast cancer
shows that tamoxifen works better than rival Eli Lilly and Co’s
(LLY.N: ) Evista, but with a greater risk of some other cancers
and blood clots.

After nearly seven years of follow-up, researchers found
that women who took tamoxifen for five years were less likely
to develop breast cancer than those who took Evista, known
generically as raloxifene.

But they told a meeting of the American Association for
Cancer Research that both drugs are useful and that women
should be able to choose. Only tamoxifen is approved for women
who have not yet gone through menopause, and many may not want
to risk its side effects.

Tamoxifen was originally sold by AstraZeneca Plc (AZN.L: )(AZN.N: ) under the brand name Nolvadex and is now available
generically. Both drugs are in a class known as selective
estrogen receptor modulators.

The researchers on the so-called STAR trial calculate that
tamoxifen lowers the risk of breast cancer in high-risk women
by 50 percent, compared with 38 percent for Evista.

Overall, both drugs also saved lives.

“There is no statistically significant mortality difference
between the two treatment groups,” the team, called the
National Surgical Adjuvant Breast and Bowel Project, wrote in
the journal Cancer Prevention Research.

After 81 months of follow-up, 236 women who took tamoxifen
had died of any cause, compared with 202 who took raloxifene.

When the researchers first reported their findings from the
STAR trial of more than 19,000 women in 2006, there was little
difference between the two drugs. Now the differences are
clearer, perhaps because raloxifene is less potent than
tamoxifen, said the researchers, who were led by Dr. Victor
Vogel of the University of Pittsburgh.

“The updated results reported here demonstrate that after
a median follow-up of 81 months, which represents 60 months of
treatment plus an additional 21 months of follow-up, raloxifene
no longer appears to be as effective as tamoxifen in preventing
primary invasive breast cancer,” the researchers concluded.

SIDE EFFECTS

Tamoxifen’s side effects are clearer after more years of
study, however. It prevents breast cancer for as long as 15
years. But it raises the risk of rarer diseases such as uterine
cancer, while Evista does not.

Tamoxifen also raises the risk of blood clots in the leg —
called deep-vein thrombosis — which can travel to the lungs to
cause a pulmonary embolism.

“The superiority of tamoxifen over raloxifene in reducing
breast cancer risk comes with a cost: significantly more
endometrial cancers, hysterectomies for benign disease,
thromboembolic events, and cataracts,” the researchers wrote.

“These toxicities may be acceptable for the treatment of
breast cancer but have proved to be a barrier to the use of
tamoxifen for preventing primary breast cancers.”

Women therefore may be more likely to take raloxifene.

“Our results demonstrate that raloxifene (compared with
tamoxifen) retains substantial benefit in reducing the risk
of invasive breast cancer and has fewer life-threatening side
effects, including significantly fewer endometrial cancers,”
the researchers wrote.

Women are only eligible to take either drug if they have a
high risk of breast cancer — for instance, if they have had
cancer in one breast and want to prevent it from coming back in
the other, if they have a genetic risk of breast cancer, or if
they have had a benign tumor called ductal carcinoma in situ.
(Editing by Lisa Von Ahn)

Long term, tamoxifen stops more cancer than Evista