Extra pounds—even within the overweight but not obese range—are linked
to a higher risk of recurrence of the most common type of breast cancer
despite optimal cancer treatment, according to a new study published
early online in CANCER, a peer-reviewed journal of the American Cancer
Society. The study’s results suggest that extra body fat causes hormonal
changes and inflammation that may drive some cases of breast cancer to
spread and recur despite treatment.
Women who are obese when they are diagnosed with breast cancer have an
increased risk of dying prematurely compared with women of normal
weight. In this new study, Joseph Sparano, MD, of the Albert Einstein
College of Medicine’s Montefiore Medical Center, in Bronx, NY, and his
colleagues across the US cancer cooperative groups compared the health
outcomes of obese and overweight patients with others in a large group
of women with stage I-III breast cancer who had participated in three
National Cancer Institute–sponsored treatment trials led by the Eastern
Cooperative Oncology Group (now part of the ECOG-ACRIN Cancer Research
Group). All of the trials (E1199, E5188, and E3189) required
participants to have normal heart, kidney, liver, and bone marrow
function, thereby excluding patients with other significant health
issues. As a result, researchers were able to disentangle the influence
of obesity from other factors affecting cancer recurrence and survival.
The researchers found that increasing body mass index—a measure of the
body’s fat content—significantly increased women’s risk of cancer
recurrence and death, despite optimal treatment including chemotherapy
and hormonal therapy. There was a stepwise relationship between
increasing body mass index and poor outcomes only in women with hormone
receptor–positive breast cancer, the most common type of breast cancer
that accounts for approximately two-thirds of all breast cancer cases in
the United States and worldwide.
“We found that obesity at diagnosis of breast cancer is associated with
about a 30 percent higher risk of recurrence and a nearly 50 percent
higher risk of death despite optimal treatment,” said Dr. Sparano.
“Treatment strategies aimed at interfering with hormonal changes and
inflammation caused by obesity may help reduce the risk of recurrence,”
he added.
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