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Understanding how genes affect cancer risk and treatment

MUSC Hollings Cancer Center

March 1, 2022

Josh Birch


Understanding how genes affect cancer risk and treatment


Knowledge is power – that’s a message Libby Malphrus, a genetic counselor at MUSC Hollings Cancer Center, tells her patients. Malphrus has seen demand for Hollings’ genetic counseling program increase by over 400% in the past two years. Hollings’ program is supported by two full-time genetic counselors, along with a growing support team, in order to meet the demand more fully as more patients become eligible for testing. “We are seeing that patients really understand the role that genetics can play in cancer risks and prevention,” Malphrus said. “If a patient is found to be at higher risk for breast cancer, that patient may need to start her mammogram at the age of 25 or 30, instead of 40. Our goal is to catch cancers as soon as possible and even try to prevent them in the first place.” Malphrus knows firsthand the importance of knowledge when it comes to personal cancer risks and a cancer diagnosis. At the age of just 33, she underwent a radical hysterectomy after being diagnosed with invasive cervical cancer.


“At the time, my mom had just been diagnosed with ovarian cancer,” Malphrus said. “I was due for my annual screening the next month, and I almost skipped it. I’m so incredibly thankful that I didn’t skip that screening.” Malphrus is a fierce advocate for men and women to receive annual screenings to know their risk factors and be better able to detect cancer earlier with proactive screenings to keep advanced cancers from developing. She knows screenings could be the difference between life and death, which is why she is quick to educate patients about the role genetics can play when it comes to cancer development and cancer risk.


Genetic mutations only account for between 5% and 10% of all cancers. That is why Malphrus said it is also important for patients to make positive lifestyle choices. Previous research indicates that around 42% of cancer cases in the U.S. are linked to excess weight, poor diet and lack of physical exercise. Alcohol and tobacco use also are linked to an increased risk of cancer. For patients with cell mutations, genetic testing remains a very important resource. Malphrus said she is excited to see eligibility for these services expand to include cascade testing so that more patients can receive potentially lifesaving information. Cascade testing refers to the genetic counseling and testing provided to blood relatives of individuals who have been identified with specific genetic mutations. “This is an exciting service. If a doctor has a patient who tests positive for a genetic mutation that makes that patient at a higher risk of cancer, then that patient’s family members could also be eligible to be tested.”


Malphrus said genetic testing can be even more beneficial for ovarian, pancreatic, breast and prostate cancers. Researchers have already identified genes in these cancers that, if identified, place a patient at a higher risk for cancer development. These genes can be inherited, which is why genetic counseling for the family members of a first- or second-degree relative with a history of cancer can also be beneficial. First degree refers to relatives who share approximately 50% of a person's genes – a parent, full sibling or child.

Second degree refers to those relatives who share 25% of the same genes: a grandparent, grandchild, half-sibling, aunt, uncle, niece, nephew, cousin.


To care more effectively for patients with genetic mutations, Hollings opened the new Hereditary Cancer Clinic, which is one of the first in the nation. Kevin Hughes, M.D., Hollings director of Cancer Genetics, said the clinic will provide patients with a centralized location for ongoing care that offers them comprehensive and effective management from a team of specialists. “Our goal is to minimize cancer mortality,” Hughes said. “We believe managing care and screening guidelines for this group of patients who are at an extremely high risk of cancer will help us diagnose and treat cancer earlier and hopefully prevent it all together.”


New areas to test

When genetic testing began in the 1990s, Malphrus said they were only able to look at one or two genes. Now, that number has exploded to 84.


“We are constantly discovering new genetic causes of cancer,” she said. “More and more genes are added on an almost yearly basis to provide patients a better understanding about their risks.”


Malphrus is also excited about the In Our DNA SC program that was announced by MUSC in 2021. The large-scale program is designed to improve health care outcomes by integrating genetic insights into clinical care and research. The statewide initiative aims to enroll 100,000 patients in genetic testing over the next four years at no cost to the patient. Patients will receive results that will tell them whether they are at a higher risk for cancer. Data collected through the project will also enable further research to provide more personalized care for patients. “I’m excited about the project because even though guidelines are expanding and we are learning more about the genetic role in cancer, we are still missing a lot of people who are carrying one of these high-risk genes, and they don’t know it,” she said. “What this project does is make genetic testing more equitable and improves access for everyone regardless of where they live or their financial situation.”


Expanding the role of circulating DNA

Hollings understands that genetic mutations are just one factor that can lead to higher risks of cancer. It’s one of the reasons Hollings is proud to offer some patients with non-small cell lung cancer access to cutting-edge technology like circulating DNA, otherwise known as liquid biopsies.


Gerard Silvestri, M.D., a Hollings pulmonologist, said circulating DNA testing enables doctors to detect cancer, discover new cancer biomarkers and determine if treatment is working in real time. Past research has shown that tumor cells release small pieces of their DNA into the bloodstream. These tests allow doctors to identify that DNA in order to learn more about a person’s specific cancer and provide personalized care. “Understanding the genetic makeup of a patient’s cancer allows us to better identify treatments that we believe will target the traits of that specific type of cancer,” Silvestri said. “These tests can also potentially identify a cancer recurrence earlier by alerting us to one or more of these cancer biomarkers in the blood.” Silvestri said circulating DNA testing is just one of the new ways to personalize care for cancer patients. “If I can understand the pathways in the body these tumor cells are using to grow, then hopefully I can interrupt them and truly provide patients with personalized therapy and medication for their specific conditions.” Silvestri said while progress has been made in cancer genetics, more research is needed to examine the effectiveness of circulating DNA in every cancer type and stage.


The future of genetic testing

Malphrus said she believes the genetics of cancer will continue playing an important role in cancer care moving forward. “I think what the future of medicine looks like is a patient would come in and give a sample of blood or saliva and get a printout of his or her genome sequence. That report would show that patient what conditions they may be at a higher risk for, which will provide information about what they should focus on when it comes to screening and surveillance.” Patients interested in genetic testing should talk with their doctors to see if it would be beneficial.

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