Even so, "this provides encouragement to patients with metastatic breast cancer" who were the focus of the study, said lead author Dr. Stephen Chia, a medical oncologist at the British Columbia Cancer Agency. "We can tell them that we have more drugs available, and it appears they do allow them to live longer."

Breast cancer is the most commonly diagnosed type of cancer, and only lung cancer kills more women.

Researchers have had a difficult time figuring out whether newer drugs, including the class called aromatase inhibitors, are effective for the most serious forms of breast cancer. It's considered unethical to assign one group of terminal cancer patients to a drug and give others a placebo or simply keep them comfortable.

"We're making a leap of faith as to what we're doing, how we're spending our resources, that we're actually allowing them to live longer," Chia said.

The new study looked at patients in the Canadian province of British Columbia between 1991 and 2001. All the 2,150 women had metastatic breast cancer, meaning tumors had spread beyond the breast.

The researchers found that the average survival time in the 1991-1992 and 1994-1995 periods was fairly stable, at 438 and 450 days, respectively. But when new drugs became available in the middle of the decade, survival grew to 564 days (1997-1998) and 667 days (1999-2001).

The newer medications included chemotherapy drugs and drugs known as aromatase inhibitors that tinker with estrogen levels. The study doesn't prove conclusively that the drugs lead to higher life spans, but the authors wrote that it seems likely.

An increase in life span of about eight months may not seem like much. But Chia pointed out that it's an average, and some women live longer.

In addition, he said, the newer drugs appear to be easier on patients, so they have better quality of life during their final days.

The results are in the Sept. 1 issue of the journal Cancer.

Dr. Eric Winer, director of the Breast Oncology Center at the Dana-Farber Cancer Institute in Boston, said the newer drugs are, indeed, easier for patients to tolerate.

"They're not only more effective, but they're kinder and gentler than they used to be. On a daily basis, our waiting room is filled with women, many of whom have advanced breast cancer but don't look different from those with early stages of breast cancer," he said.

But Winer noted that the study, which was first reported four years ago, is a bit outdated, because it was done before Herceptin (trastuzumab) was approved in 1998.

Herceptin allows about a quarter of women with breast cancer to survive for years, he said. The drug works best in those with HER2-positive cancer.

But, he added, "There are many women who are only living a year or two or three with this illness. We want it to be much better than that."

Meanwhile, another study published in the journal followed up on a previous study assessing the value of group therapy in breast cancer patients.

The case-control trial found that patients in weekly group therapy had only similar survival rates to those given literature-based patient education.

But the study also found that group therapy improved the quality of life for women with estrogen-receptor-negative tumors.

More information

Learn more about breast cancer from the National Cancer Institute.