Wednesday, May 22, 2024

Understanding hereditary cancer syndromes: identifying high-risk patients

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The underlying mechanism of the transformation of a normal cell into a cancerous cell lies in the acquisition of faults in the genes. This is why cancer is called a genetic disease. The faults in the genes can be acquired (multifactorial), resulting in sporadic cancer, or they can be inherited from the parents, causing hereditary cancers. The body has a mechanism to repair these faulty genes (DNA repair mechanisms), which prevents the development of cancer.

Most sporadic cancers are preventable (up to 50%) just by avoiding exposure. Still, as we grow older, the multiplying cells eventually fail to repair the genetic alteration(s), which is why cancer is considered a disease of aging. On the other hand, inherited genetic alterations that are passed on from one generation to the next put you at a higher risk of developing cancer and cannot be corrected. Inheriting a cancer-related genetic change doesn’t mean you will definitely get cancer. The reason being that every gene has two copies (one from the mother and the other from the father); the normal gene reduces the cancer probability over the abnormal gene. But sometimes, if the normal gene becomes abnormal, it can increase the risk of developing cancer. If an individual is carrying abnormal genes, they can be passed on to the next generation. These are known as hereditary cancer syndromes. The carriers in the next generation can be identified through genetic testing and can be put on various cancer preventive strategies like preimplantation genetic diagnosis (PGD) and selection of embryos for prevention of alteration getting passed on to offspring.

Some of the hereditary cancer syndromes are:

Hereditary Breast and Ovarian Cancer (HBOC): This syndrome usually affects family members affected by breast and/or ovarian cancer at an early age. Most often, the inherited genetic alteration observed in HBOC is in the BRCA1 and BRCA2 genes, but it may also have other alterations. The risk of breast and ovarian cancer is very high in women with mutations in either BRCA1 or BRCA2. This syndrome can also lead to fallopian tube cancer, primary peritoneal cancer, male breast cancer, pancreatic cancer, prostate cancer, etc.

Lynch syndrome: This syndrome usually causes people to have an increased risk of developing colorectal cancer at an earlier age, often less than 50. Lynch syndrome is caused by genetic alteration in any of several mismatch repair (MMR) genes, including MLH1, MSH2, MSH6, PMS2, and EPCAM, which are normally involved in repairing damaged DNA. Lynch syndrome also leads to a high risk of endometrial cancer and cancers of the ovary, stomach, small intestine, pancreas, kidney, brain, skin, breast, prostate, and bile duct.

Li-Fraumeni Syndrome: This is a rare inherited syndrome that can lead to an increased risk of a number of cancers, including sarcoma, leukemia, brain cancers, and breast cancer. These cancers often develop in relatively young adults or even children.

There are many other rare hereditary syndromes (like Cowden syndrome, Peutz-Jeghers syndrome, Von Hippel-Lindau syndrome, Familial Adenomatous polyposis, and many more) that can be seen in families, and people with a strong family history may be intrigued to know about their genes.

Identifying high-risk individuals for Hereditary cancer syndromes can be made possible with proper testing and genetic counseling sessions by qualified professionals. Undertaking the test can be a complex personal decision made for different reasons, but it is best made after talking with your family and experts like a molecular oncologist, cancer geneticist, and cancer genetic counselor.

These individuals can be recognized by the following signs:

1) Multiple cancers run in the family across generations (significant family history)
2) Multiple cancers in one person (syndromic presentation)
3) Cancer occurring in paired organs like bilateral breast cancer
4) Cancer occurring at a younger age than usual (early onset)
Rare cancers like male breast cancer and others.

(The author, Dr. Amit Verma, is a molecular oncologist and Cancer Geneticist)

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