To guide molecular testing in the management of patients with cancer, the College of American Pathologists (CAP) and three collaborating societies are seeking comments on an evidence-based clinical guideline they are developing for testing DNA mismatch repair (MMR) and microsatellite instability (MSI) status in patients with a range of cancer types.
The other societies collaborating on the guideline are the American Society of Clinical Oncology (ASCO), the Association for Molecular Pathology (AMP), and Fight Colorectal Cancer (Fight CRC). The panel will consider all comments garnered during the comment period prior to finalizing the recommendations and submitting the guideline for publication.
The groups opened the public comment period for the guideline, MMR and MSI Testing in Patients Being Considered for Checkpoint Inhibitor Therapy on February 19 and want to receive recommendations before March 13.
“This guideline is the first to address testing based more on the methodology status of a biomarker and less on the cancer type or tumor origin,” explains Russell Broaddus, MD, PhD, FCAP, who chairs the panels of experts collaborating on the guidelines. “As we’ve learned more about patient response to checkpoint inhibitor therapy, we’ve seen that patients whose cancers had high levels of MSI, or defective MMR would respond well, specifically to a checkpoint inhibitor drug such as pembrolizumab.”
CAP noted that while the Food and Drug Administration (FDA) approved a drug for patients with MSI-high or MMR-deficient tumor status, regardless of cancer type, it did not detail how to test for that status. “The guideline aims to fill that gap and provide oncologists, pathologists and laboratories of all sizes with evidence-based recommendations to efficiently deploy specific assays and accurately identify patients eligible for treatment,” CAP said.
In developing the draft guideline, the collaborating societies sought to answer the following questions:
· Which test modality best predicts DNA mismatch repair?
· Do MMR by immunohistochemistry, polymerase chain reaction, or next-generation sequencing predict improved clinical outcomes in patients treated with checkpoint inhibitors?
· Does tumor mutation burden predict improved clinical outcomes in patients treated with checkpoint inhibitors?
Clear guidance is essential because many of the “new biomarkers have associated high costs both in the form of capital and reagent expenditures or as send out tests,” CAP noted.