Breast Cancer Chemo: Lower Dose for Obese?
Study Questions Dose Reductions for Overweight Patients
June 13, 2005 -- Overweight or obese women with breast cancer may benefit
from getting a full dose of chemotherapy, says a new study in the Archives
of Internal Medicine.
However, some doctors may be reducing chemo doses for such patients, say the
researchers, who included Jennifer Griggs, MD, MPH, of the University of
"Overweight and obese women with breast cancer often receive
intentionally reduced doses of adjuvant chemotherapy," say Griggs and
colleagues. Receiving a full, weight-based dose "is likely to improve the
outcomes in this group of patients," they write in the journal's June 13th
That's especially important these days, with obesity rising in the U.S.,
according to the study.
What's Weight Got to Do With It?
is widely used after breast cancer surgery. Breast
cancer is the most common cancer among U.S. women, except for nonmelanoma skin
cancers. More than 211,000 new cases will be diagnosed this year, says the
American Cancer Society.
Obesity is a risk factor for developing breast cancer. It can also worsen
the prognosis for breast cancer patients, say Griggs and colleagues. But they
don't want to oversimplify matters. Many factors are involved in the
obesity-breast cancer association, they say.
Doctors may cut chemo doses for patients who aren't in good health (apart
from their cancer). Some small studies have shown that some chemotherapy drugs
linger longer in the bodies of obese patients, but Griggs and colleagues say
"there is little evidence to support the use of dose reductions in these
Chemotherapy Dose-Weight Study
Griggs' study looked at doses of two chemotherapy drugs -- doxorubicin and
cyclophosphamide -- in more than 9,600 women with breast cancer treated at
about 900 practices.
Most were healthy, except for their breast cancer; few had other serious
medical problems. They were treated from 1990 to 2001.
More than six out of 10 women were overweight or obese (31% overweight, 17%
obese, and 14% severely obese), says the study. Chemo doses were reduced for
37% of the severely obese women, 20% of obese women, and 11% of overweight
Overweight is defined as a
or BMI of
25-29.99; a BMI of 30-39.99 is obese, and 40 or higher is morbid or severe
The practices took different approaches; some didn't cut back at all on
chemo doses for heavier patients.
More than half (about 500 practices) had at least five patients who were
overweight, obese, or severely obese. A third of those practices didn't reduce
chemo doses. Another 10% only cut the dose in 10% or fewer of their
However, a small percentage of practices (9%) reduced the first-cycle dose
in more than half of their overweight or obese patients. Few patients at any of
the study's practices got higher doses after the first chemo cycle.
Long-Term Effects Unknown
The study didn't focus on long-term survival or cancer recurrence.
In the short-term, women who were overweight, obese, or severely obese were
not more likely to be hospitalized for chemo-related drops in white blood cells
(febrile neutropenia), regardless of their chemo dose. In fact, severely obese
women were less likely to be hospitalized for that health problem, says the
Evidence is gathering that "obese patients do not experience increased
toxic effects when dosed according to actual body weight," say the
researchers. Calculating chemo doses based on actual body weight is associated
with "improved disease-free and overall survival in heavy patients,"