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 Researchers examined data from 88 clinical trials involving 62,923
women with estrogen receptor (ER)-positive tumors. After treating
ER-positive tumors with chemotherapy, radiation or surgery, women
typically get five years of follow-up therapy with daily
hormone-based pills – either tamoxifen or aromatase inhibitors. The
goal of the adjuvant therapy is to destroy any lingering cancer
cells not killed by initial treatment.
All of the women were cancer-free when they completed five years of
adjuvant hormone-based therapy.
During the next 15 years, however, cancer returned for 41% of the
highest-risk women in the study who originally had the largest
tumors that had spread the most beyond the breast, the study found.
Even the lowest-risk women who originally had small tumors that
hadn’t spread to the lymph nodes or other parts of the body still
had 10% odds of cancer coming back during the study, researchers
report online November 13 in the New England Journal of Medicine.
“We know that adjuvant (hormone-based) therapy for 5 years
substantially reduces the risk of recurrence and mortality,” said
senior study author Dr. Daniel Hayes of the University of Michigan
Comprehensive Cancer Center in Ann Arbor.
“We now have good evidence that extending adjuvant (hormone-based)
therapy beyond five years continues to suppress and reduce
recurrence and mortality,” Hayes said by email.
Doctors have long known that five years of tamoxifen reduces
recurrence by approximately half during treatment, and by nearly a
third over the next five years. Aromatase inhibitors, which work
only in post-menopausal women, are even more effective than
tamoxifen at reducing recurrence and death from breast cancer.
Some recent research suggests an additional five years of
hormone-based therapy is even more effective, but the side effects
make some women reluctant to continue. Life-threatening side effects
are rare, but women taking these hormones can have menopause
symptoms like hot flashes and vaginal dryness.
The data suggest that women with ER-positive breast cancer should at
least consider continuing adjuvant therapy beyond five years, the
authors conclude.
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“Breast cancer cells can travel from the primary tumor to the lymph
nodes and can circulate throughout the body undetectable with
current screening (methods) and over time, these circulating cancer
cells can attach to other organs in the body and this is generally
when there is a detectable cancer recurrence,” said Albert Farias, a
cancer researcher at the Keck School of Medicine of the University
of Southern California in Los Angeles who wasn’t involved in the
study.
“One way that adjuvant breast cancer treatment works is to kill
and/or stop the undetectable cancer cells from growing and
dividing,” Farias said by email.
Even though the study suggests some women may have more risk of
recurrence based on their original tumor characteristics, it can
still be hard to predict and women need to remain vigilant, said Dr.
Sharon Giordano of the University of Texas MD Anderson Cancer Center
in Houston.
“Breast cancer can be dormant for many years, so that women can have
no apparent disease, but can still recur years later if the tumor
becomes active again,” Giordano said by email. “We do not know why
some cancers become active again after years of dormancy.”
Women need regular checkups and breast screenings, as well as annual
mammograms, said Dr. Alana Biggers, a researcher at the University
of Illinois-Chicago who wasn’t involved in the study.
“If a woman is high risk for breast cancer, such as a lady with a
gene mutation, she may need both mammograms and breast MRIs,”
Biggers added by email. “Additionally, women should maintain a
healthy weight, exercise, stop smoking, and limit alcohol
consumption to reduce their risk of recurrence.”
SOURCE: http://bit.ly/2AWSttH
N Engl J Med 2017.
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