PARIS, Aug 30, 2019 (BSS/AFP) – Hormone therapy to relieve menopause
symptoms slightly increases the risk of breast cancer, according to a large-
scale study published Friday in The Lancet.
Other research has established a similar link, but the new study is the
first to show that the risk remains elevated even ten years after treatment
has stopped.
It also quantifies for the first time the level of risk associated with
different types of menopause hormone therapy, or MHT.
The chance that a women between 50 and 69 who has never undergone MHT will
contract breast cancer is about 6.3 in a 100.
By comparison, a woman in that age bracket who takes oestrogen and,
intermittently, progestagen for five years stands a 7.7 in 100 chance of
getting the disease.
If — in the same scenario — progestagen use is daily, the risk goes up
again: 8.3 in 100.
Finally, an oestrogen-only regimen is closest to the no-hormones baseline,
with a 6.8 out of 100 risk.
More prolonged use carries even higher risk, said co-author Gillian Reeves
from the University of Oxford.
“Use of MHT for 10 years results in about twice the excess breast cancer
risk compared to five years of use,” she said in a statement.
“But there appears to be little risk from use of menopausal hormone therapy
for less than one year.”
The topical use of vaginal oestrogens, applied as a cream, is also
relatively risk-free, she added.
– Halved abruptly –
Women tend to begin MHT at the start of menopause when ovarian function
ceases, causing oestrogen levels to fall substantially.
At the same time, progesterone levels fall to near zero.
As a consequence, many women experience uncomfortable “hot flushes” that
can be alleviated by replacing the naturally depleted hormones.
Regulatory bodies in Europe and the United States recommend that MHT be
reduced to the shortest time needed, but usage has tended to average at least
five years.
In North America and Europe, MHT increased rapidly during the 1990s, halved
abruptly in the early 2000s, and then stabilised about ten years ago.
“Our new findings indicate that some increased risk persists even after
stopping use of MHT,” said co-author Valerie Beral, a professor at the
University of Oxford.
Beral and colleagues examined data from 58 previous studies around the
world from 1992 to 2018 that recorded MHT use. Within the data set, 108,647
women subsequently developed breast cancer, at an average age of 65.
Researchers were then able to look for statistical links between cancer
rates, on the one hand, and type along with duration of treatment, on the
other.