Overview of Cancer Genetic Counseling

Cancer is the second leading cause of death in the United States, with just under 600,000 people dying of cancer in 2017 alone. With the detrimental effect of cancer, it is no surprise that there has been extensive research into causes and cures. There have been many advances in the treatment of cancer including chemotherapy, immunotherapy and targeted therapy. Beyond looking for treatments, the early detection of cancer is vital in increasing the success of treatment. Early detection is largely dependent on education and the promotion of screening and detecting warning signs.

A cancer genetic counselor’s primary role is to help to identify the familial risk of cancer. The most common reasons for patients being referred to genetic counseling are a current or previous cancer diagnosis or a family history of cancer. For patients with cancer, a genetic counselor’s role is to help the patient understand genetic risk, its implications on their treatment and their family’s associated risk. As for patients with a family history of cancer, a genetic counselor’s main role is identifying the potential for genetic risk and the implications on prevention measures.

For both types of patients, cancer genetic counselors, either before or during the appointment, review the medical records and familial history with patients to create a pedigree. Taking a family history includes knowing family members who had cancer, what was the type of cancer, what was the age of diagnosis and did they have cancer multiple times. Strong indicators of a potential genetic factor include many family members with related and rare cancers or tumors, and family members being diagnosed with cancer at a younger age. The pedigree created helps to inform the likelihood of a genetic predisposition to cancer and what genetic panel would be most informative of the patient’s risk.

The most common cancers seen by genetic counselors are breast/ovarian and colorectal cancers due to the most gene mutations being known for these. Mutations are known for other cancers such as endocrine, genitourinary, skin, brain/ nervous system, sarcoma and hematologic, but overall there are only 84 genes that can be tested by Invitae’s Multi-Cancer Panel. This is very few compared to the 175 genes which can be tested in
Counsyl’s recessive carrier screening. This just shows how much research is still occurring and how much the field has room to grow.

When a positive result comes back for a patient it is fairly common for cancer genetic counselors to see other members of that patient’s family who are also concerned about their risk. This familial component is a major reason why patients receive cancer genetic testing — they are worried about family members such as siblings and children. With positive genetic testing results, patients are recommended to start preventative care earlier in hopes of detecting and treating cancers at an earlier stage. Preventative care includes screening tests, vaccines and making healthy choices. Some screening tests include mammograms, Pap smears and colonoscopies. The human papillomavirus (HPV) vaccine protects against HPV strains which are associated with cancers. Healthy choices patients can make include not using tobacco, limiting sun exposure, limiting alcohol consumption and maintaining a healthy weight and lifestyle. These healthy life choices as a preventative measure are a reminder that many factors contribute to cancer development, and though patients with a positive genetic testing result have a higher risk of developing cancer in their lifetime, it is not a definite this will occur. Additionally, for those who do not wish to receive genetic testing if there is a family history of cancer, the same early preventative care measures are recommended. Patients may not desire genetic testing for a variety of reasons including that genetic testing may not be covered by health insurance or the patient is not ready to know this result for family planning or personal reasons.

For patients who have a cancer diagnosis and are receiving genetic counseling, there are targeted treatments that have been developed for certain mutations. These targeted treatments are drugs and antibodies which are more effective in treating cancers with specific gene changes, or understanding which treatments are not effective for certain mutations. In treating r colorectal cancer, cetuximab and panitumumab are less effective for tumors with specific mutations in the RAS gene. These advancements in treatment using genetics display the booming need and importance of genetic counselors in the oncology field.

By Carolyn Maxwell

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