Shirley Michelle Shiller, DO, member of the Precision Medicine Institute's Advisory Committee, Baylor University Medical Center, discusses molecular testing in gastrointestinal cancers.

Molecular markers have increasingly driven selection for therapies in the gastrointestinal space, says Shiller. Some of the most impactful agents have been PD-L1 inhibitors for gastric cancer, but it is important to note that the interpretations of the tests are different than the ones used in the lung, Shiller explains.

Mismatch repair deficient (dMMR) and microsatellite instability-high (MSI-H) tumors are also important to identify, as there are specific agents that have shown efficacy in patients who harbor those alterations. For example, pembrolizumab (Keytruda) is currently approved for the treatment of adult and pediatric patients with unresectable or metastatic, MSI-H or dMMR solid tumors, as well as for patients with MSI-H or dMMR colorectal cancer following progression on a fluoropyrimidine, oxaliplatin, and irinotecan. When looking at this space, Shiller says that it is important to utilize markers that screen for hereditary predisposition to gastrointestinal cancers. Several sites of origin—apart from the colon&mdash;have been seen in patients with hereditary syndromes.

Videos

Dr. Shiller Discusses Molecular Testing in Gastrointestinal Cancers

Shirley Michelle Shiller, DO, member of the Precision Medicine Institute's Advisory Committee, Baylor University Medical Center, discusses the difficulties that are preventing a more streamlined approached in testing for biomarkers.

Some of the main challenges that physicians are facing are the FDA issuing companion diagnostics without adequately engaging the pathologist in terms of its performance characteristics. Physicians also need to work together to streamline which markers are being used, such as PD-L1.

Though there are FDA companion diagnostics in other spaces, for years the testing was also done in labs throughout the country with similar results—results that weren't overseen, governed, or given a companion diagnostic designation by the FDA.

Going forward, physicians have to develop a better level of communication with the FDA in terms of the performance of assays and help them understand that physicians are already governed by 2 other parties. Having a third party come into the mix may or may not be needed depending on the actual biomarker and how it’s going to be used.

Dr. Shiller on the Challenges in the Development of NSCLC Biomarkers

Shirley Michelle Shiller, DO, member of the Precision Medicine Institute's Advisory Committee, Baylor University Medical Center, discusses the emerging technology of liquid biopsies and the clinical success associated with them.

Though liquid biopsies have been used predominantly in the domain of lung cancer, doctors are still learning a lot about the procedure. Biopsies can be plasma- or urine-based, though less is understood about urine-based testing. Plasma-based testing, though best understood in the sphere of lung cancer, has potential to be used for colon cancer.

Detection rates are lower in plasma than in solid tumors because there is more experience testing solid tumors. In comparison, there are other variables that cannot be controlled as much in plasma-based testing. When taking a biopsy of a solid tumor, the tumor is clear on the slide, whereas it is less clear when blood is drawn whether the tumor is shedding at that time, or that the mutations are shedding in enough of a quantity to be detected.

Shirley Michelle Shiller, DO, member of the Precision Medicine Institute’s Advisory Committee, Baylor University Medical Center, discusses the emerging technology of liquid biopsies and the clinical success associated with them.

Shirley Michelle Shiller, DO

Articles

Dr. Shiller Discusses Molecular Testing in Gastrointestinal Cancers

Dr. Shiller on the Challenges in the Development of NSCLC Biomarkers

Dr. Shiller on the Emergence of Liquid Biopsies