Research presented at a just-concluded breast cancer symposium will help doctors understand how to use existing drugs better when certain drugs don't work, and how chemotherapy may not be to blame for so-called "chemo brain."

Breast cancer doctors and researchers from around the world gathered at the San Antonio Breast Cancer Symposium in San Antonio, Texas, last week to learn about the latest developments in treating the disease.

Here are some of those latest developments:

1. 'Chemo brain' starts before chemo

It's been known for a long time that when women undergo breast cancer treatment, they can have trouble remembering regular tasks and jobs. Chemotherapy, or so-called "chemo brain," has often been blamed. There's still no good explanation for why this happens or how to treat it.

Doctors are concerned about this because patients' concerns over "chemo brain" may result in a reluctance to accept life-saving therapy, said Bernadine Cimprich, an associate professor emerita at the University of Michigan School of Nursing in Ann Arbor, who presented a new study at SABCS.

Using an MRI, her team tested patient's brain function while performing a working memory task in the scanner. This was done before any chemotherapy started and a month after treatment was completed.

The study involved a total of 97 participants: 28 patients receiving chemotherapy, 37 patients who got radiation therapy and 32 healthy women.

The results showed that women who were scheduled to undergo chemotherapy had the lowest activation of the part of the brain that is critical for the effective performance of a working memory task: The left inferior frontal gyrus.

Women who were not able or less able to activate the frontal brain region suffered greater fatigue over time, regardless of treatment, Cimprich said. Also, women expecting chemotherapy were more worried and more fatigued than the other groups, including the radiation group.

Cimprich believes there's a need for increased awareness that cognitive problems can begin before a woman starts chemotherapy after her tumor is removed, including letting women know that as they wait for chemotherapy to start, they are more vulnerable to cognitive problems related to worry and fatigue.

She said "chemo brain" may not be an appropriate label for cancer-related cognitive dysfunction because there are likely other sources that contribute to the problem or produce problems that wouldn't exist otherwise.

2. Twice as long is better with the drug tamoxifen

When breast cancer patients take the hormone-blocking drug tamoxifen for 10 years instead of five, they can significantly reduce their chances of the cancer coming back or of dying from it, according to new data from an ongoing clinical trial called ATLAS or Adjuvant Tamoxifen -- Longer Against Shorter.

About a decade ago, the National Cancer Institute recommended premenopausal women with a type of cancer that is fueled by estrogen (called estrogen-positive breast cancer) should only take tamoxifen for five years after they've had tumors surgically removed.

The argument was that there wasn't sufficient data to justify it taking longer, according to Dr. Peter Ravdin, director of the breast cancer program at the University of Texas Health Science Center at San Antonio. While tamoxifen has been known to have a residual effect of another five years after a patient stops taking it, "about one-third of relapse in estrogen-positive patients occur after five years," Ravdin said.

Researchers from England, however, report that after taking tamoxifen for 10 years, the risk of a woman's cancer coming back was reduced by 30% and the risk of dying from the cancer was reduced by nearly half.

These aren't the final results of the ATLAS trial, which is a huge clinical trial. Nearly 13,000 women were enrolled between 1996 and 2005, and researchers presented eight-year follow-up data from about 7,000 of them at SABC.

There are side effects from taking this drug, including an elevated risk of endometrial cancer. But the risks are far smaller than the benefits, say researchers. Tamoxifen has been around long enough that a generic version is available and costs about $100 per month.

Once the final results of ATLAS are in and it's compared to other similar studies, the standard of care for these patients will probably change from five to 10 years, according to the editorial accompanying the study in The Lancet.