Studies Shed New Light on Breast Cancer, Treatment
THURSDAY, Sept. 6 -- New studies from the first annual Breast Cancer Symposium shed light on racial differences in breast cancer, how not sticking with treatment can affect survival, and how nagging side effects cause people to stop their therapies.
The symposium, held in San Francisco, is co-sponsored by the American Society of Breast Disease, the American Society of Breast Surgeons, the American Society of Clinical Oncology, the American Society for Therapeutic Radiology and Oncology, the National Consortium of Breast Centers, and the Society of Surgical Oncology.
An estimated 180,000 new cases of breast cancer will be diagnosed in the United States in 2007, and more than 40,000 people will die from the disease. After lung cancer, breast cancer is the second leading cause of cancer death in women.
Although the overall incidence of breast cancer is lower in black women than white women, survival rates are lower among black women. Black women also have a higher incidence of the disease at younger ages and tend to be diagnosed at later stages.
Experts point to socioeconomic factors as the reason for much of this discrepancy, but, as one study presented at the meeting showed, the tumor's biology also plays a role.
After analyzing data on more than 170,000 cases of breast cancer in both black and white U.S. women, investigators concluded that, among invasive cancers, estrogen receptor (ER)-negative tumors were significantly more frequent in black women at all stages of the disease and in all age categories.
ER-negative tumors have a less favorable prognosis than ER-positive tumors, which have more treatment options.
Thirty-nine percent of black women had ER-negative tumors compared with 22 percent of white women.
Black women were also diagnosed at a younger age (57 years of age on average for black women versus 62 for white women) and at a later stage of the disease (29 percent of black women were stage 1 versus 42 percent of white women).
"We need to understand this better, to give these women as good an outcome as we can," said study lead author Dr. M. Catherine Lee, a clinical lecturer in the department of surgery at the University of Michigan Comprehensive Cancer Center in Ann Arbor, at a Wednesday teleconference.
A second study found that 10 percent of women filled 70 percent or less of their prescriptions for tamoxifen, a drug taken by many cancer survivors to prevent recurrences.
Tamoxifen has been shown to reduce the recurrence of ER-positive breast cancer when used after primary treatment. Women who often skipped tamoxifen had a 16 percent increased risk of death compared to women who filled all their prescriptions, the researchers noted.
Although the study did not look specifically at why women were dropping the treatment, side effects may play a role.
"Most women who take tamoxifen know it can have substantial and life-affecting side effects such as hot flashes, which can make life misery," said Dr. Alastair Thompson, lead author of the study and a professor of surgical oncology at the University of Dundee in Scotland. "It could be that those sorts of side effects we've downplayed in the past are factoring in," he said.
"Taking your pills really matters," added Dr. Julie Gralow, moderator of the teleconference and associate professor of medical oncology at the University of Washington School of Medicine in Seattle.
A third and final study found that 13 percent of women taking aromatase inhibitors -- drugs that inhibit the production of estrogen for ER-positive breast cancer patients -- stopped this treatment due to musculoskeletal side effects such as rotator cuff tendonitis, carpal tunnel syndrome and osteoarthritis.
Overall in the trial, 42 percent of women reported some sort of musculoskeletal side effect.
"There were a surprising number of women who stopped therapy," acknowledged Dr. N. Lynn Henry, study lead author and a clinical lecturer at the University of Michigan Comprehensive Cancer Center. "But we were unable to find predictive factors. We need more research."
It was also unclear why the aromatase inhibitors were causing these aches and pains.
"We need to acknowledge that this is something that is truly affecting our patients, and we need to figure out the mechanism for these symptoms and how best to manage them so our patients can get this important treatment," Gralow said.
Most of the women who discontinued treatment with aromatase inhibitors switched to another therapy, Henry said.
For more on breast cancer, head to the U.S. National Cancer Institute.
Posted: September 2007