Women with Lynch syndrome are at 40-60% greater risk of endometrial cancer - a cancer that begins in the lining of the uterus, called the endometrium.
It is estimated that around 1 in 440 Americans possess a gene mutation associated with Lynch syndrome.
The condition is most commonly associated with greater risk of colorectal cancer, accounting for around 3-5% of all cases. Women with Lynch syndrome, however, are also at 40-60% greater risk of endometrial cancer - a cancer that begins in the lining of the uterus, called the endometrium.
According to the American Cancer Society, around 54,870 women in the US will be diagnosed with endometrial cancer this year. Lynch syndrome accounts for around 2-5% of all cases.
Study co-author Aung Ko Win, of the University of Melbourne in Australia, and colleagues note that at present, hysterectomy is the only factor recognized as reducing the risk of endometrial cancer among women with Lynch syndrome.
Past studies have indicated that hormonal factors - such as hormonal contraceptive use and later age at first menstrual cycle - may be linked to lower risk of endometrial cancer among the general population, though Win and colleagues note it is unclear whether this is the case for women with Lynch syndrome.
Hormonal influences on endometrial cancer risk may apply to women with Lynch syndrome
With the aim of finding out, the team analyzed data of 1,128 women with an MMR gene mutation. The women were a part of the Colon Cancer Family Registry and were recruited from centers in the US, Canada, Australia and New Zealand between 1997 and 2012.
Information was gathered on diagnosis of endometrial cancer among the women, as well as data on age at first menstrual cycle, hormonal contraceptive use, the number of live births, age at first and last live birth, age at menopause and postmenopausal hormone use.
The researchers found women with an MMR gene mutation who started their menstrual cycles later - defined as age 13 or older - those who had one or more live births and those who had used hormonal contraceptives for at least 1 year had a lower risk of endometrial cancer.
The team found no association between age at menopause, age at first and last live birth and postmenopausal hormone use and reduced risk of endometrial cancer.
Win and colleagues say their findings indicate that some hormonal factors that have been linked with reduced endometrial cancer risk among the general population may also apply to women with Lynch syndrome. They add:
"If replicated, these findings suggests that women with an MMR gene mutation may need counseling like the general population in regard to hormonal influences on endometrial cancer risk."