Martha Polovich, PhD, RN, AOCN®
In the course of an average day, a medical oncologist may have to break terrible news to several patients, telling them they have cancer, or that their disease has recurred.
In comparison, sitting down in a quiet room to write out a prescription for chemotherapy might seem much less nerve-wracking.
But oncologists know that’s not always the case. For those who treat overweight or obese cancer patients, choosing doses of chemotherapy can be a sweat-producing endeavor. While some physicians prescribe the way they do for normal-weight patients— based on body surface area (BSA), a calculation of height and weight—others cap the amount of chemotherapy for larger patients, for fear that full doses will spark too many side effects.
“You’re sometimes talking about really whopping doses of drugs, and it makes everyone a little nervous,” said Martha Polovich, PhD, RN, AOCN®, director of Clinical Practice for Nursing Education and Research at Duke Oncology Network. “If you have a 300-lb breast cancer patient with a BSA of 2.56, many oncologists would cap the BSA at 2.0 and give 120 mg of doxorubicin. If you dosed based on the actual BSA, you’d give 150 mg. It’s more than we’ve ever given in the past.”
Now, however, oncologists are being encouraged to give full doses without the worry. A clinical practice guideline1 issued in April by the American Society of Clinical Oncology (ASCO) recommends that chemotherapy doses—particularly those with curative intent— be based on full body weight in obese patients, unless it is contraindicated due to comorbidities.
Dosing based on body weight will improve a trend toward poorer outcomes among heavy patients without increasing toxicities, according to the guideline, which is based on an ASCO expert panel’s review of data on the topic published over 46 years.
The guideline does not address the dosing of radiation or targeted cancer therapies.
Jennifer Griggs, MD, MPH
Many Patients Affected
Currently, up to 40% of obese cancer patients are given reduced chemotherapy doses, ASCO has said.2
Yet a 1996 study by Rosner, et al3
demonstrated that underdosing such patients by even 6% can compromise their chances of survival, noted Jennifer Griggs, MD, MPH, associate professor in the Departments of Internal Medicine and Health Management & Policy at the University of Michigan, and a member of the ASCO expert panel that drafted the guideline.
The issue affects a significant number of patients with cancer. According to the guideline, more than 60% of America’s adults are overweight, obese, or morbidly obese. The World Health Organization defines overweight people as those who have a body mass index (BMI) of 25 to 29.9 kg/m2
; obese individuals as those with a BMI of 30 kg/m2
or more; and morbidly obese people as those with a BMI over 40 kg/m2
Gary Lyman, MD, MPH, professor of Medicine in the Division of Medical Oncology, Department of Internal Medicine at Duke University School of Medicine and the Duke Cancer Institute, North Carolina, proposed several years ago that ASCO draft a guideline on chemotherapy dosing in the overweight and obese population. By then, he said, cooperative organizations for clinical cancer research, including Cancer and Leukemia Group B and the Eastern Cooperative Oncology Group, had recommended against the capping of chemotherapy doses in obese patients. Yet, practice varied widely throughout the country, with dose capping occurring in both academic and community oncology settings.
ASCO convened an expert panel to investigate the issue, chaired by Lyman and Griggs.
Gary Lyman, MD, MPH
“We felt as a society and as a panel that this was a guideline that was probably long overdue, and was going to become even more important because of the rising wave of obesity in patients we see in our clinic,” Lyman said. “Obese patients should have the same chance at curative treatment as healthy-weight individuals.”