Family history of breast cancer does not increase risk of womb cancer

A family history of breast cancer does not increase a woman`s chances of developing womb cancer, finds a 20-year study in the Journal of Medical Genetics.

Cancers of the lining of the womb (endometrium) and breast share some of the same reproductive, hormonal, and lifestyle risk factors. The evidence for a genetic link between the two types of cancer has so far been inconclusive.

But a team from the US National Cancer Institute and the Uniformed Services University of the Health Sciences in Bethesda, Maryland, investigated whether women who had a family history of breast cancer were more likely to develop endometrial cancer than women with no such family history. They studied this in over 37,500 former participants of a US national breast screening programme (the Breast Cancer Detection Demonstration Project).

The women were monitored for an average of almost 14 years during the study, which started in 1979 and completed in 1998. Their average age was 55 at the start of monitoring. Information was also collected on any cases of breast cancer among their first and second degree female relatives.

During the study, endometrial cancer was diagnosed in 648 women. There was no evidence that breast cancer in either a first or second degree relative predisposed to the development of endometrial cancer, after taking account of influential factors, such as age, use of hormone replacement therapy, previous breast cancer diagnosis and family size.

Furthermore, the development of endometrial cancer was not affected by the number of relatives who had had breast cancer, nor the age at which they had been diagnosed. But women with a first degree relative who had cancer in both breasts had a slightly increased risk of endometrial cancer. However, there was no evidence of hereditary cancer syndromes, such as early age at diagnosis or high rates of breast cancer among family members.

Women who had already had breast cancer themselves were 30 per cent more likely to develop endometrial cancer, but a family history of breast cancer had no bearing on this.

The authors conclude: “a family history of breast cancer does not seem to be an important endometrial cancer risk factor, although a personal history of breast cancer does increase the risk.”