Cancers du sein et risques génétiques

Breast cancer: hereditary risk factors

Mathilde Regnault
04/02/2017
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It is estimated that some 120,000 women in France are predisposed to breast and/or ovarian cancer. The aim is to identify them in order to be able to offer effective care.

Two genes contributing to breast-cancer susceptibility have been identified to date: BRCA1 and BRCA2, which are located respectively on chromosomes 17 and 13. Some 60,000 women are thought to carry one of these two genetic mutations. They may be transmitted by either parent and significantly increase the risk of one day developing breast or ovarian cancer. The actress Angelina Jolie, whose mother and aunt both died of the disease, is also a carrier of this mutation. That is why she opted to undergo a preventive mastectomy and ovary removal. Some 60,000 other women are carriers of a mutation that increases the risk of developing cancer, in a gene that is not yet identified.

The toughest challenge is to identify these patients carrying mutations. A large number of breast cancers in one family may point to a hereditary factor, but this is not always the case. Similarly, it is not necessarily true that a person in the family who has not been affected does not carry the mutation, which may, for example, have been passed on by the father.

There are some 100 genetic-oncology consultation locations throughout France. Their aim is to identify and prevent hereditary cancers. The physician will put together a family history and, based on this, will recommend genetic testing or not.

Several criteria may lead a person to seek a genetic consultation.

Individual criteria.

  • Breast cancer before the age of 36.
  • Medullary breast cancer, regardless of the age at diagnosis (specific form of breast cancer).
  • Ovarian cancer diagnosed before the age of 70 (excluding germ tumors and borderline tumors).
  • Men who have developed breast cancer before the age of 70 (though this limit can be debated on a case-by-case basis).

Family criteria.

  • At least three cases of breast cancer among first- or second-degree relatives, regardless of the age at diagnosis.
  • Two cases of breast cancer among first- or second-degree relatives through the male line, with at least one case diagnosed before the age of 40, or one case diagnosed before the age of 50 and the other before the age of 70.
  • One woman suffering from breast cancer and at least one first-degree relative, or second-degree relative through the male line suffering from ovarian cancer, regardless of the ages at diagnosis (and vice versa).