Genetic testing holds great promise, but there are some critical drawbacks to consider.
Genetic testing in its various forms may be used to identify increased risk of health problems, choose treatments, or assess responses to treatment. “While this can generally be a low risk to an individual’s overall health-it can be difficult financially or emotionally for a patient to learn their results,” says Suman B. Rao, MD, medical oncologist, MedStar Franklin Square Medical Center.
RaoSpecifically, in regards to biomarker testing, which is what a clinician may use to make treatment decisions, the test is performed using a sample of a patient’s tumor, although in some cases it can be performed on a blood sample.
In non-small cell lung cancer, for example, the process usually requires a surgical procedure to remove tumor tissue from the lung, which has potential risks. In many cases, biomarker testing can be done on the sample that was originally used to diagnose the lung cancer initially. But in some cases, a patient may need another biopsy to obtain enough tissue for biomarker testing.
“Not all patients will have identifiable biomarkers and not all biomarkers have treatments associated with them, so it can be discouraging for a patient to learn that’s the case,” Rao says.
Another downside from a patient perspective is if an insurance company obtains information related to biomarkers and consequently denies or limits coverage, adds Nathan Wei, MD, FACP, FACR, director, Arthritis Treatment Center.
Here are two other downsides to consider:
1. False positives – though the number is decreasing
From the clinician side, more investigation is necessary to optimize the use of biomarkers. “Although the technology is available, a significant investment in bioinformatics is necessary to achieve analytical and technical validity of testing,” says Massimo Cristofanilli, MD, associate director for precision medicine and translational research at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University at Northwestern Memorial Hospital. “Furthermore, linking clinical data to genomic data will ultimately prove the clinical utility of testing and provide the rationale for identifying biological information-in view of the fact that testing will reflect disease biology and represent a false negative or false positive result.” On the positive side, “The rate of error is decreasing tremendously due to the large number of patients being treated and improvements in technology.”
Dennis Holmes, MD, breast cancer surgeon and interim director, Margie Petersen Breast Center at John Wayne Cancer Institute at Providence Saint John’s Health Center, says a main downside to genetic testing is its cost, which varies depending upon the number of mutations being tested. Further, “Patients and physicians need to realize that a negative test result does not necessarily mean that an individual’s cancer risk is not elevated, especially if cancer is prevalent in that individual’s family,” he says. “In such a case, a negative test result may simply mean that the test did not identify genetic factors contributing to breast cancer risk in that patient’s family. There still is a role for risk reduction and prophylactic measures in families where cancer prevalence is high, but where no harmful genetic mutation has been detected.”
As a breast cancer specialist, Holmes says his greatest concern is that genetic testing is under-utilized, not over-utilized, leaving many mutation carriers undetected until after they have been diagnosed with a potentially preventable mutation-related cancer.