Advances in breast cancer have greatly improved long-term survival.

In a 15-year follow-up involving 145,000 women with early-stage breast cancer, researchers found that a woman's risk of dying from breast cancer was cut in half when she received six months of chemotherapy and five years of hormone therapy.

This is very good news," study researcher Sarah Darby, PhD, tells WebMD. "Women with breast cancer should feel very enthusiastic about the therapies that are out there. They are very good."

Long-Term Benefits

Cancer survival is typically reported in terms of five-year survival. But many people want to know how likely they are to live 10 or 15 years — or more.

Darby found that breast cancer treatments following surgery have had a significant impact on breast cancer survival 15 years down the road.

In fact, survival advantage at 15 years among women who got chemotherapy vs. those who didn't was about twice that reported five years after initial breast cancer treatment. The benefit for five years of tamoxifen vs. none was almost three times greater at 15 years than at five.

The combined effect of the two treatments is largely responsible for a drop in deaths from breast cancer in the U.S., the U.K., and other industrialized countries over the past decade and a half, Darby says.

Tracking the Survival Advantage

The researchers tracked women who participated in 194 trials evaluating follow-up breast cancer treatments in the 1980s and early to mid-1990s. Tamoxifen was the only hormone treatment used when the studies were conducted.

Roughly three out of four breast cancer patients have tumors that grow in response to hormones — called hormone sensitive — and are candidates for estrogen-targeting treatments like tamoxifen.

With appropriate chemotherapy and hormone therapy, a 50-year-old woman who previously had a one-in-five chance of dying from her breast cancer would have a one-in-10 chance of dying, according to the researchers.

The study is published in the May 13 issue of the journal The Lancet.

"A woman with breast cancer detected very early might have a 20 percent risk of dying of her disease without chemotherapy and tamoxifen, and a 10 percent risk with it," Darby says. "So for every 100,000 women treated, there would be 10,000 deaths instead of 20,000."

The impressive survival advantage seen in middle-aged, hormone-sensitive patients treated with six months of anthracycline-based chemotherapy and five years of tamoxifen confirms the value of this well-established treatment approach, Darby says. Examples of anthracycline drugs used for breast cancer include Adriamycin and Ellence.

"This is the largest analysis of randomized evidence ever done in any type of cancer," she says. "Because so many women in previous decades agreed to join these randomized trials, millions of women in future decades will benefit."

Findings Point to Cure

In an editorial accompanying the study, oncologist Stephen Chia, MD, and colleagues wrote that the findings provide strong evidence that follow-up chemotherapy and hormone therapy actually cure women of their breast cancer, rather than delaying the cancer's recurrence.

"It is now clear that these treatments cure a significant proportion of women with early-stage breast cancer," Chia tells WebMD. "When we look at breast cancer survival curves out to 15 years there is a significant difference between women who got chemotherapy vs. no chemo and women who got five years of tamoxifen vs. none," he says.

But Chia questions the value of continuing to follow this large group of women for another five years. Anthracycline-based chemotherapy and tamoxifen are still widely used, but Chia says researchers might learn more by including patients treated with newer drugs in future studies.

For example, recent studies have shown that newer hormone therapies, such as Arimidex and Femara, may be even more effective than tamoxifen.

"I think it would be useful to utilize this major resource to look at these newer treatments rather than updating the same treatment in five years," he says. "I'm not sure that we will see any added value at 20 years vs. 15."

By Salynn Boyles, reviewed by Michael W. Smith, MD

SOURCES: Darby, S. The Lancet, May 14, 2005; vol 365: pp 1687-1711. Sarah Darby, PhD, professor of medical statistics, University of Oxford, England. Karen Gelmon, MD, FRCPC, British Columbia Cancer Agency, Vancouver. Stephen Chia, MD, oncologist, British Columbia Cancer Agency, Vancouver.