Genetics of hereditary cancer

Between 5-10% of all cancer cases are related to genetic alterations that are inherited, i.e. passed down through families. Having an inherited genetic change does not always mean that one is irrevocably destined to get cancer, but rather that there is an increased risk of developing a certain type or types of cancer. New genes for hereditary predisposition to different types of cancer are becoming better known.

Inherited cancer occurs when a genetic change that increases the risk of cancer is passed down through families. Being born with this change means that a person has a higher chance of developing specific types of cancer, and these cancers may occur at a younger age than in other people who do not have the change. It is now recommended that a larger number of genes be studied through more efficient sequencing of multigene panels.

Some cancers have specific characteristics that suggest that a risk may have been inherited from a parent, even when there is no significant family history of cancer.

• Breast cancer that is described as “triple negative” (negative results when tested for the presence of certain proteins in tumour tissue on biopsy analysis).
• Ovarian cancer that is described as high-grade serous (this includes similar cancer in the fallopian tubes or peritoneum).
• Cancer in the colon or uterus (endometrium) that is described by the absence of some proteins when tests are performed on the tumour.

Some people who undergo colonoscopy and have more polyps than expected, or unusual polyps, which may also suggest an inherited cancer risk.

The main goal of genetic diagnosis of a predisposition to hereditary cancer is the intervention and follow-up of the affected patient and his or her family with the aim of reducing mortality caused by cancer.

Cancer-related genetic testing provides guidance for decision making. The purpose of performing a predisposition test for hereditary cancer is to recommend follow-up and preventive measures adapted to the identified risk and to inform individuals and their families to discuss different preventive measures, ranging from strict periodic follow-up to – in some cases – the extreme of sometimes recommending preventive surgery (e.g. preventive mastectomy, colon resection, removal of ovaries and tubes, etc.).

A person should consider genetic screening for hereditary cancer if:

• You have several first-degree relatives (mother, father, siblings, children) with cancer.
• Many relatives on one side of your family have had the same type of cancer.
• If you know that a certain type of cancer in your family is related to a genetic alteration.
• A relative has more than one type of cancer or bilateral cancers e.g. in both breasts.
• A family member has had cancer at a younger age than normal for that type of cancer.
• A relative has a rare cancer, such as breast cancer in a man or retinoblastoma (a type of eye cancer).
• A physical finding that is related to an inherited cancer (such as having many polyps in the colon).
• One or more family members have already had a genetic test that found a genetic alteration.

If you have concerns about cancer in your family, talk to your doctor. Bring any information you have about family members who have had cancer. Also talk to your family members to find out if anyone has already started this process. Reviewing this information can help you and your doctor decide whether genetic testing is needed.

At Veritas we have an expert team of medical geneticists who could guide you. Contact us