A new study has a bit of good news for most women who’ve had breast cancer surgery.

It turns out that sticking with the older and relatively cheap drug tamoxifen for the recommended 5 years instead of just 2 will cut the risk of having the cancer return.

And there is an added bonus: For women in their 50s, the longer drug treatment also reduced the chance they’d develop heart disease.

“That little nugget is very exciting,” said Dr. Harold J. Burstein, a breast cancer expert at Harvard Medical School in Boston who was not involved in the study.

Tamoxifen, sold as Nolvadex and Soltamox in the U.S., has long been the drug of choice for early-stage breast cancer that responds to estrogen. That accounts for at least 70 percent of cases.

Doctors also prescribe newer drugs called aromatase inhibitors once women have gone through menopause, which may work slightly better than tamoxifen.

But because the prognosis for early-stage breast cancer is generally good these days, a potential benefit on heart disease - the leading killer worldwide - may be worth pursuing for patients at high risk, said Burstein.

“That will be part of the dialogue with patients,” he told Reuters Health.

The price tag for the two kinds of drugs is another thing to consider. According to the authors of the report, tamoxifen costs between $40 and $100 per month in the U.S. - less in developing countries - while aromatase inhibitors may run as high as several hundred dollars.

The new study is published in the Journal of Clinical Oncology by Allan Hackshaw of Cancer Research UK and colleagues. It’s a follow-up study from an earlier trial by Cancer Research UK, the nation’s leading cancer charity organization.

The women included were anywhere from 44 to 80 years old and had early breast cancer in one breast. After 2 years of daily tamoxifen treatment, nearly 3,500 participants were randomly assigned to either stay with the drug for another 3 years or stop taking it.

Fifteen years later, the cancer had returned in 40 percent of the women who got the longer treatment and in 46 percent of those who got the shorter one.

In other words, 17 women would need to take tamoxifen for 5 years instead of 2 to prevent one cancer recurrence in the same breast.

“This is very consistent with all the previous data,” said Burstein. “It’s great to have long-term follow-up from these clinical trials.”

The difference in death from breast cancer at 10 years was only 1.4 percent, however, and might have been due to chance.

The study also shows that women taking tamoxifen for a longer period may reduce heart disease, at least among women in their 50s.

After 15 years, there were seven fewer heart attacks and strokes per 100 women taking tamoxifen for 5 years compared to 2, and three fewer deaths from those diseases.

Tamoxifen does have side effects, the researchers note, such as hot flashes, blood clots and cancer of the womb.

But the serious side effects are rare. According to the National Cancer Institute, for example, cancer of the uterine lining occurs in about two per 1,000 women taking tamoxifen compared to one per 1,000 women taking an inactive placebo pill.

Conclude the researchers: “Women should be encouraged to continue with their adjuvant tamoxifen therapy for the current recommended target duration of 5 years.”

SOURCE: Journal of Clinical Oncology, online March 21, 2011.