Women who undergo hysterectomies often have both ovaries removed along with
the uterus in order to prevent ovarian cancer. But a new study suggests
ovary removal may increase the risk of another seemingly unrelated ailment,
lung cancer.
University of Montreal scientists stumbled onto the connection while
investigating the relationship between lung cancer and hormones in women.
They found no relationship between hormonal factors like menstruation
patterns, child-bearing or breast-feeding histories and the risk of lung
cancer. The researchers did, however, discover that women whose menopause
had been induced medically were at 1.92 times greater risk of developing
lung cancer than women who had experienced natural menopause.
“We were surprised — we had no prior expectation of this finding,” said
Anita Koushik, a researcher at the University of Montreal’s Department of
Social and Preventive Medicine and the first author of the study, published
online in May in The International Journal of Cancer. “Aside from the fact
that smoking increases your risk of lung cancer, the results of this study
suggest that having a non-natural menopause contributes to an almost
doubling of the risk.” She noted, though, that the findings could have
occurred by chance.
The vast majority of women who had experienced a non-natural menopause had
had both ovaries surgically removed, she added.
While smoking is the leading cause of lung cancer, other factors may play a
role in enhancing the impact of the carcinogens in tobacco, Dr. Koushik
said. In women, these factors could be hormonal. Both normal and cancerous
lung tissue express estrogen receptors and may be influenced by levels of
the hormone in the body, Dr. Koushik said. The patterns of expression are
different in men and in women.
Medically induced menopause usually occurs at a younger age than natural
menopause. Surgical menopause results in a sudden drop in estrogen levels,
compared with the more gradual decline in hormone levels that occurs with
natural menopause. Dr. Koushik suggested the increased lung cancer risk may
be linked to the impact of plummeting hormone levels.
In the study, the scientists examined data on 422 women diagnosed with lung
cancer in the greater Montreal area in 1996 and 1997 and compared them with
577 randomly selected control subjects. The women were asked about a variety
of hormone-related factors, including when they got their first periods, how
many children they had, whether they breast-fed their children and whether
they had gone through menopause. The researchers also gathered detailed
information about smoking, occupational history, education and family
income.
The report is not the first to link ovary removal with an increased risk of
lung cancer. A recent analysis of data from the Nurses’ Health Study,
published in the journal Obstetrics and Gynecology in May, reported that
women who had had hysterectomies but kept their ovaries lived longer than
women who had had the procedure but whose ovaries were removed.
While those who had their ovaries removed were less likely to develop breast
cancer and virtually eliminated their risk of ovarian cancer, they were more
prone to heart disease and were at greater risk for other kinds of cancer,
including a doubling of the risk for lung cancer among those women who never
used hormone therapy.
