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Mom or Dad Had Cancer. Does That Mean I’ll Get It?

If your mom or dad had cancer, you may be worried about what this means for your own health somewhere down the road.

While it is true that some cancers have genetic links, the vast majority of these diseases are unrelated to genes passed down in families. Considering how common cancer is, most of us can point to multiple family members who have dealt with one cancer or another. Current research suggests that only 5 percent to 10 percent of cancers are hereditary.

Generally speaking, cancers develop because of an unfortunate mutation in one of the 20,000 genes found in the human body. These mutations cause the gene to malfunction, at which point it may become cancerous and start multiplying.  Hereditary cancer occurs when a mutation in a cancer-related gene is passed down in the family. 

Finding Hereditary Links

When assessing whether a particular cancer runs in your family, there are several factors your medical team will consider. These include:

  • Cancer developing in family members while they were young, particularly before the age of 50.
  • Cancer found in multiple close relatives on the same side of the family.
  • Relatives diagnosed with the same cancer, or different cancers caused by the same gene mutation.
  • Genetic testing revealing a gene mutation in one of your relatives with cancer.
  • Cancer occurring in the sex not usually affected (breast cancer in men, for example).
  • Cancer occurring in both sets of organs (both eyes, kidneys or breasts, for example).

The likelihood of a cancer having hereditary links varies significantly from cancer to cancer. Only about 1 percent of lung cancers, for example, are hereditary. On the opposite end of that spectrum, there are some cancers found in children that are 89 percent hereditary. And some cancers – ovarian cancer, for example – have strong genetic links and raise immediate concerns.

All in the Family, not in the Genes

When a cancer does appear to run in a family, it’s more likely that the culprit will be a shared environment. An easy way to look at this is to go back 50 to 100 years when lung cancer was commonly found to run in families. That’s not surprising, when you consider that smoking was much more common then.

Or look at Florida, where it’s not uncommon to find melanoma – a serious type of skin cancer – in multiple family members over a couple generations. While melanoma can have genetic links, it’s more likely in the Sunshine State that excessive sun exposure is to blame.

This illustrates one of the difficulties in determining whether a cluster of cases is hereditary or simply the result of a group of people with similar genetics reacting to the same environmental factors.

And then there’s the bad luck factor. There are families that experience similar cancer cases, without any obvious explanation why. That’s increasingly true as people live longer lives. Unfortunately, age is one of the biggest risk factors for cancer. So, as generations live longer, cancer incidents will rise.

When To Get Genetic Testing

If your medical team is concerned that your family may share an abnormal gene linked to cancer, genetic counseling may be suggested. Genetic counseling helps individuals learn if the cancer in their family may be hereditary and determine their risk of developing cancer.  If genetic testing is warranted for a family, testing will be recommended for the family member who’s been diagnosed with the cancer in question.

Testing may reveal a more accurate assessment of your (and your family’s) risk for a particular cancer. And as a result, it could give you a chance to better manage your risk through lifestyle changes, medication, surgery or more frequent screenings. If you have a hereditary risk for colon cancer, for example, your doctor may recommend a colonoscopy every one or two years, instead of every five to 10 years. It could also change treatment strategies if you’ve already been diagnosed with cancer.

Genetic tests are available for a variety of cancers, including:

  • Breast cancer
  • Ovarian cancer
  • Colon cancer
  • Thyroid cancer
  • Prostate cancer
  • Pancreatic cancer
  • Melanoma
  • Sarcoma
  • Kidney cancer
  • Stomach cancer

There are some potential pitfalls with genetic tests. If the test reveals no known genetic cancer links, that puts you back to square one in terms of figuring out why a cancer is common in your family.

And if the test does confirm the presence of an abnormal gene, that doesn’t automatically mean something bad will happen. In some cases, the gene creates only a slightly higher risk. Even with the more dangerous mutations, there is no guarantee of cancer. Consider that about 12 percent of women will develop breast cancer. There are some gene mutations that will double that risk, while others (the well-known BRCA genes, for example) could increase the breast cancer risk to as high as 80 percent.

It's also important to understand that genetics is a fast-growing area of medicine. Researchers are constantly refining and finding new gene associations with cancer and other diseases. As a result, anyone who had genetic testing done 10 years ago may benefit from additional/updated genetic testing. If you believe that your family may benefit from genetic counseling/testing, please ask your doctor for a referral to a genetic counselor.

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