Breast cancer patients who are less educated and have a lower household income are more likely to receive reduced doses of chemotherapy -- leading to undertreatment for their disease -- new research suggests.
Overweight and obese women are also more likely to receive less chemotherapy.
The report is published in this month's issue of the Journal of Clinical Oncology.
Researchers looked at 764 women with early breast cancer who were enrolled in a prospective, multi-center study of cancer patients starting chemotherapy.
Using U.S. Census Bureau statistics and zip codes, the study authors estimated each woman's household income and poverty status. The women were also interviewed to determine their level of education.
What they found was that women with less education were more than three times as likely as those with more education to receive reduced levels of chemotherapy.
Typically, doctors use a formula -- based on a patient's height and weight -- to determine what dose of chemotherapy patients should receive during treatment. But the women in this study didn't always receive as much chemotherapy as they should have, according to the study.
"What we saw was that women who had not completed high school were far more likely to be started on a lower dose [of chemotherapy]," said study co-author Dr. Gary Lyman, professor of medicine and oncology at the University of Rochester Medical Center in Rochester, N.Y.
"Why that might be, we really don't know," Lyman said. "We are collecting more data and hope to dissect out to the reasons for this undertreatment."
Undertreatment with chemotherapy is a very serious problem for breast cancer patients and cancer patients in general.
This finding sheds light on a very real discrepancy -- women with less money and less education are being given less of the medicine they need.
The study is an important first step in addressing the discrepancies, cancer experts say.
"This study is significant," said Dr. Clifford Hudis, Chief of the Breast Cancer Medicine Service at Memorial Sloan-Kettering Cancer Center in New York.
"Undertreatment of patients with chemotherapy is a broad problem," Hudis said. "It has been called 'killing with kindness," and it is important to understand where and how it happens so that we can address the issue."
Women who are overweight are also likely to be under treated with chemotherapy, the new research confirms.
Obesity is controversial as a risk factor for breast cancer; studies haven't shown that obesity causes breast cancer, but obese women are at increased risk of dying from the disease.
Scientists estimate that between 11,000 and 18,000 deaths per year from breast cancer in U.S. women over age 50 might be avoided if women could maintain a Body Mass Index under 25 throughout their adult lives.
The lower survival rates in heavy women may be associated with higher levels of estrogen production in these women.
However, they may not do as well because they are treated differently.
"Many drugs are dosed based on a calculation of the body surface area that uses both height and weight," said Hudis. "For larger people this leads to larger doses, sometimes at levels that concern clinicians."
"This leads them to err in the direction of underdosing to avoid harm."