THURSDAY, Jan. 18, 2007 (HealthDay News) -- Poorer women with breast cancer are more likely to receive reduced doses of chemotherapy from their doctor, a new study suggests.
And less-educated women, as well as obese women, are also more likely to get reduced chemotherapy doses. Severely obese women in the study were four times more likely than lean women to receive less chemotherapy, and those with less than a high school education were three times more likely to get a reduced dose, the researchers said.
The study, by researchers at the University of Michigan Comprehensive Cancer Center, is published in the Jan. 20 issue of the Journal of Clinical Oncology.
"Many of these decisions are actually subconscious," Dr. Jennifer Griggs, lead author of the study, said of the findings. "I don't believe doctors set out to give anything but the best of care."
Griggs, an associate professor of internal medicine at the University of Michigan Medical School, suggested that the decisions to give lower doses of chemotherapy are based on benevolence.
"Doctors are concerned that patients who have less social support and fewer resources [including financial ones] are going to be less likely to continue therapy if they get the full dose" and perhaps more side effects, she said.
As for giving obese women reduced doses, Griggs said she suspects the concern is safety. Chemotherapy doses are based on body surface area, with heavier women having more surface area. Some doctors may fear that a dose based on body surface area would be too much if a woman is very heavy, she said.
But Griggs added that her interpretations of the study results were based on speculation, because the research did not include interviews with doctors.
For the study, Griggs and her colleagues evaluated 764 women who were in a cancer registry and were being treated for early breast cancer with chemotherapy, among other regimens. Study participants were enrolled at 115 hospitals and doctors' offices across the country. The researchers looked at data on household income, education, and body mass, and then evaluated correlations with doses of chemotherapy.
It has long been known that breast cancer survival rates are lower among poorer women, even though the incidence of breast cancer is lower among these women. Griggs said her findings may help explain this apparent paradox.
Chemotherapy dose matters most for the type of breast cancer known as estrogen receptor-negative, or ER negative, Griggs said,. "Up to a third to a half of breast cancers are ER-negative, depending on age," she said.
Griggs and her colleagues published a small study in 2003 with similar findings, she said, adding that the new study was larger and confirms the earlier results.
Another expert, Dr. Christy Russell, a medical oncologist and associate professor of medicine at the University of Southern California's Keck School of Medicine in Los Angeles, called the study interesting.
Russell said similar findings have been discussed at medical meetings, and efforts are already in place to educate doctors about dosing issues and patient compliance. "Many patients say, 'The side effects are too bad, can you lower the dose?' " she said.
As for the finding of reduced doses for obese women, Russell said that might be due to a doctor's training. "Some of us were trained to cap off the chemo," she said. Very heavy women would get the same dose as someone who was simply heavy. These approaches are changing, however, with most now not recommending a cap, she said.
Dosing of chemotherapy is traditionally not a decision shared by physicians and patients, Griggs said. "But women should be aware of this pattern," she said. "They should feel free to ask their doctor how the dosing decision has been made."
Russell agreed. "Women need to be aware and have the discussion with their physician that they anticipate they will be given the full dose of chemotherapy," she said.
To learn more about breast cancer and treatment, visit the U.S. National Cancer Institute.