Dr. Kopetz on the Rarity of Fusions in CRC

Scott Kopetz, MD, PhD, FACP, associate professor, Department of Gastrointestinal Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, discusses the rarity of fusions in patients with colorectal cancer (CRC).

Patients with fusions comprise a very small percentage of the overall population of patients with CRC, explains Kopetz. The most common fusions are those in RET, ALK, FGFR, and NTRK. In total, the overall occurrence of fusions in CRC is likely less than 1%, says Kopetz. Because of their rarity, fusions are not routinely tested in practice. Though there is value in their identification, there remains debate over the best way to detect them, Kopetz adds.

Notably, fusions tend to overlap with microsatellite instability (MSI), which is associated with high and durable responses to PD-1 and CTLA-4 blockade. In July 2018, the FDA approved the combination of nivolumab (Opdivo) and ipilimumab (Yervoy) for pediatric and adult patients with MSI-high or mismatch repair deficient metastatic CRC following progression on a fluoropyrimidine, oxaliplatin, and irinotecan.