Weighty Issues: Do You Know How Chemotherapy Should Be Dosed for Overweight Patients?

Lisa Schulmeister, RN, MN, APRN-BC, OCN®, FAAN

Editor-in-Chief OncLive Nursing

Oncology Nursing Consultant, Adjunct Assistant Professor of Nursing Louisiana State Health Sciences Center in New Orleans, Louisiana

According to the Centers for Disease Control and Prevention (CDC), 36% of adults in the United States are now obese. Add to that the 33% who are overweight, and that leaves a minority of our population weighing in at a healthy weight. And if the obesity trend continues at its current pace, the obesity rate in America will be 44% by 2030, according to a recent study from the Trust for America’s Health and the Robert Wood Johnson Foundation.

As clinicians, we’ve witnessed the adaptive measures that healthcare organizations have taken to make it more comfortable for heavier patients to receive care. These include wider, deeper treatment chairs and beds, bigger blood pressure cuffs, and larger patient gowns. Only recently have we examined the care that obese patients receive.

I’ve heard more than one patient exclaim, “I’m too fat to have cancer” when receiving a cancer diagnosis. In our well-nourished society, it’s inconceivable for some that cancer can be diagnosed in overweight people. The image almost always associated with cancer is that of the weak and cachectic.

Calculating Dosages

For years, we really didn’t know what to do when confronted by an overweight person who needed chemotherapy treatment. In years past, the obese patient was the exception and not the norm. Prescribers used a variety of methods to calculate “appropriate” dosages of chemotherapy—using a maximum body surface area, basing dosage on ideal body weight, and everything in between. What many prescribers were not doing was basing chemotherapy dosing on actual weight. However, we now know that this is the best approach.

The new practice guideline from the American Society of Clinical Oncology (ASCO), Appropriate Chemotherapy Dosing for Obese Adult Patients with Cancer, recommends that prescribers use an overweight patient’s actual body weight, rather than an ideal body weight or other estimate, to calculate the dosages of nearly all chemotherapy drugs. ASCO recommends fixed (not based on weight) dosages of a few drugs, such as carboplatin and bleomycin, and no more than 2 mg of vincristine in a single dose.

Obese patients with cancer are more likely to die from cancer than those who are not obese. This may partly reflect on the fact that an estimated 40% of obese patients are underdosed with chemotherapy when dosing is based on ideal body weight or rounded down. There is no evidence that short- or long-term toxicity is increased among overweight and obese patients receiving full weight—based dosages, and myelosuppression is the same or less pronounced among the obese than the nonobese who are administered full weight–based dosages. The ASCO guideline recommends that clinicians respond to all treatment-related toxicities in obese patients in the same ways they do for patients who are not obese.

Patient and Provider Resources

What to Know: ASCO’s Guideline on Chemotherapy Doses for Obese Patients with Cancer is available online as a patient guide at Cancer.Net (www.cancer.net). The patient guide provides background information on the dosing recommendations, explains what those recommendations mean for patients, and suggests specific questions patients can ask about their chemotherapy dosing basis, monitoring for side effects, and dosage adjustments. This is a great resource for patients and should be suggested to overweight patients, so they can be better informed and better equipped to advocate for optimal chemotherapy dosing.

ASCO also has a toolbox available on its site containing the full guidelines, data supplements, commentaries, slide sets, dosing tools, podcasts, and frequently asked questions. The slide sets may be particularly helpful to nurses who want to disseminate this information to other oncology care providers.

Getting prescribers to embrace the idea of basing chemotherapy dosing on actual weight for overweight patients is still evolving, and some uninformed prescribers remain of ASCO’s chemotherapy dosing recommendations. Oncology nurses have the opportunity to educate both their patients and their physician colleagues about appropriate chemotherapy dosing for overweight and obese patients with cancer.