Obesity and Poverty Tied to Reduced Breast Cancer Chemotherapy

ROCHESTER, N.Y., Jan. 19 -- Fatter, poorer, and less educated breast cancer patients are more likely to get partial-dose adjuvant chemotherapy, which may jeopardize their survival, researchers reported.

In a national study, severely obese women (? 35 kg/cm²) were four times as likely as lean women to receive less than 85% of the standard adjuvant chemotherapy dose, found Jennifer Griggs, M.D., now of the University of Michigan in Ann Arbor, and colleagues at the University of Rochester.

Much of this was attributable to misapprehensions about the toxicities of the higher doses of chemotherapy needed for overweight patients, the investigators reported in the Jan. 20 issue of the Journal of Clinical Oncology.

Also, patients with less than a high school education were three times as likely to be short-changed, the investigators found.

The researchers studied 764 breast cancer patients treated with a standard chemotherapy regimen at 115 randomly selected hospitals and physicians' offices across the country. The data collection, but not the study, was supported by Amgen through the University of Rochester-based Awareness of Neutropenia in Cancer Study Group Registry, a prospective, multicenter study of cancer patients starting chemotherapy.

According to Gary Lyman, M.D., of the University of Rochester, one of the investigators, 21% of obese and severely obese women received less than 85% of the standard dose, compared with 10% of the lean women. Moreover, 32% of women who didn't finish high school received reduced doses, compared with 14% of women with a high school or college education.

The use of reduced chemotherapy schedules in heavy patients is a consistent finding in previous studies, Dr. Griggs said. The motivation for this practice, which violates clinical trial protocols, is most likely physicians' desire to avoid toxicity, which they believe might accompany the large doses that patients' weight would indicate.

There appears to be persistent uncertainty among oncologists about the safety of full weight-based doses despite published research supporting the use of actual body weight in calculating doses, the investigators said.

The part played by lower socioeconomic status is less clear, they said, but appears to be physician-driven. The researchers speculated that under conditions of uncertainty, as is true with chemotherapy, physicians are more likely to be concerned about a patient's ability to communicate, shorter duration of visits, less partnership building, and less social talk in physician-patient encounters.

Negotiating a patient through treatment's adverse effects may seem more straightforward with patients of higher socioeconomic status with whom there is less social distance, the researchers suggested.

Only one prior study has examined the effect of socioeconomic status on chemotherapy dose, said Dr. Griggs and colleagues. Black race, increasing age, co-morbidities, and obesity have all been associated with underdosing for the first course of chemotherapy and overall lower dose intensity.

Social disparities in breast cancer outcomes and in mortality may be partly the result of lower chemotherapy doses in the adjuvant treatment of breast cancer, the investigators said. Efforts to address such prescribing patterns might help reduce these socioeconomic disparities in breast cancer survival, they added.

The patients, mean age 53.2, had a histologically confirmed diagnosis of nonmyeloid cancer (stages I, II, or III) and were starting a new myelosuppressive regimen with at least four planned cycles.

U.S. Census Bureau statistics and the women's zip codes were used to assign the women to a median household income, and to estimate education level.

Information was also collected about the patients' actual educational attainment, disease, and treatment, including chemotherapy doses received. The physicians calculated the standard chemotherapy dose for each patient and compared it with the dose the patient actually received.

In univariate analysis, individual education attainment, zip code socioeconomic measures, body mass index, and geographic region were all significantly associated with intentionally reduced doses of chemotherapy.

In multivariate analysis, controlling for the wide variations of geography, factors independently associated with reduced doses were obesity (body mass index of 30-35 kg/cm²) (odds ratio, 2.47; 95% CI, 1.36 to 4.51), severe obesity (OR, 4.04; CI, 1.46 to 11.19), and education less than high school (OR, 3.07; CI, 1.57 to 5.99).

A limitation of the study, the investigators said, was the assignment of socioeconomic status, which was limited to individual education attainment and zip code rather than street address, the investigators wrote.

The independent association between socioeconomic factors, controlling for geography, suggests that its impact on dosing is not merely related to local practice patterns. These results offer an explanation for the disparities in breast cancer-specific survival in patients in a lower social and economic bracket and may provide an opportunity to improve patient care and possibly patient outcome, Dr. Griggs' team concluded.

The following authors or their immediate family members indicated a financial interest. As consultants: Melony Sorbero, Ph.D., Amgen; Jeffrey Crawford, M.D., Amgen; David Dale, M.D., Amgen. Honoraria received: Dr. Griggs, Novartis, Aventis; Dr. Dale, Amgen; Gary Lyman, M.D., Amgen, GlaxoSmithKlein. Research funds received: Dr. Crawford, Amgen; Dr. Dale, Amgen; Dr. Lyman , Amgen, GlaxoSmithKlein.