New information shows inherited risk more relevant than ever

Emerging research at BC Cancer has proven that hereditary factors account for more cancer diagnoses than previously thought.

Recent advances in tumour sequencing confirm that one in 10 advanced cancer diagnoses are potentially linked to a hereditary cancer risk. This latest information also shows the connection to inherited risk spans all cancer types, not just a select few.

That’s a significant number of individuals and families who may be affected by hereditary gene mutations that put them at a higher risk of developing cancer. Early identification of gene mutations that could signal a hereditary link is done through genetic screening. Screening provides individuals and families with vital information to prevent or minimize their risk of developing cancer.

Medical geneticist Dr. Kasmintan Schrader and medical oncologist Dr. Sophie Sun lead the BC Cancer's Hereditary Cancer Program (HCP), which currently screens for the most common inherited genetic mutations (BRCA1, BRCA2 and Lynch syndrome).

Identifying risk may lead to early detection

What is hereditary cancer? Our genes are constantly mutating. Most of these mutations do not cause any health issues. But in some cases mutations can build up and lead to cancer growth or spread. In general, there are two ways in which cancer can develop. The first way is through mutations that build up due to environmental effects, such as exposure to harmful chemicals or tobacco smoke. The second way is to inherit a gene mutation that presents a higher risk of developing cancer.

Cells have to regularly divide as part of their natural life cycle, and when they do all the genetic information within the cell has to be copied. Sometimes errors occur in the copying process, and while most of them are repaired naturally those that aren’t can present what’s known as a mutation. Those mutations can then be copied to more cells and can be present in germ cells (cells that mature into gametes, which are reproductive eggs or sperm) so that they are then passed down through generations of family members.     

It’s important to note that not everyone who inherits a hereditary cancer gene will develop cancer, but they are at a higher risk than someone who didn’t inherit that gene. When someone inherits a cancer gene they have usually inherited the first mutation that may lead to cancer but it’s not just that mutation that will cause the disease. Their body has to develop or build up additional mutations in that same gene or other genes to essentially turn on a switch that tells cells to become cancer. A hereditary gene is just one variable, but it is an important one.

The goal of providing hereditary testing to individuals and members of high-risk families is to present an opportunity for early detection and prevention of certain types of cancer. By more quickly identifying those with a hereditary mutation, the HCP team aims to increase their chances of survival.

Genetic information can inform treatment plan

Hereditary testing is done on individuals who meet certain criteria, and it consists of collecting a sample of saliva or blood. Results are returned in about four to six weeks. If a mutation is identified, genetic counsellors are provided to help explain the information and how it can be used, such as implementing increased surveillance or screening (e.g. regular colonoscopies) before cancer is detected at an advanced stage.

An example of an area in need of earlier intervention is pancreatic cancer. In 2017 alone, nearly 600 British Columbians will be diagnosed with the disease. Of those patients, 75 per cent won’t survive the first year and only five per cent (30 patients) will survive five years. Pancreatic cancer is a particularly vicious foe because it’s difficult to detect at an early stage and is often resistant to treatment in advanced stages. With its numbers on the rise, pancreatic cancer is forecast to soon be the third leading cause of cancer death in Canada.

But 20 per cent of patients diagnosed with pancreatic cancer have a family history of the disease, which means early and consistent screening could help stem the tide of this insidious invader. While not all the risk factors for pancreatic cancer are known, a genetic link has been identified. BRCA1/2 and other mutations contribute to an increased risk of developing the disease. It is also believed that individuals from families with a history of pancreatic cancer (two or more diagnoses) are more likely to develop it. Knowledge about the presence of these mutations or familial connections may impact early diagnosis and treatment options.

What BC Cancer researchers are realizing more in advanced-stage cancers is that genetic testing, whether it reveals a hereditary risk or not, can help with treatment planning.

Donor funds help support the HCP team’s study and development of novel ways to better diagnose hereditary cancer in an efficient and cost-effective manner in order to reach the greatest number of families who might benefit from the information.

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