Molecular Characterization and Therapeutic Targeting of Colorectal Cancers Harboring Receptor Tyrosine Kinase Fusions.

PURPOSE

Receptor tyrosine kinase fusions in colorectal cancers are rare, but potentially therapeutically relevant. We describe clinical, molecular, and pathologic attributes of RTK fusion-associated colorectal cancer.

EXPERIMENTAL DESIGN

We identified all cases with RTK fusions in patients with colorectal cancer seen at Dana-Farber Cancer Institute (Boston, MA) who underwent OncoPanel testing between 2013 and 2018. Clinical, histologic, and molecular features were extracted from the patient charts and molecular testing results.

RESULTS

We identified 12 driver oncogenic fusions in various RTKs. These fusions occurred exclusively in and wild-type tumors and were enriched in right-sided and mismatch repair-deficient (MMR-D) colorectal cancers. All of the MMR-D colorectal cancers with RTK fusions were found in tumors with acquired MMR-D due to promoter hypermethylation and one was associated with a sessile serrated polyp. Molecular profiles of MMR-D colorectal cancer with RTK fusions largely resembled V600E-mutated MMR-D colorectal cancer, rather than those secondary to Lynch syndrome. We describe two patients with fusion-associated microsatellite stable (MSS) colorectal cancer who derived clinical benefit from therapeutic targeting of their translocation. The first harbored an fusion and received sequential crizotinib and alectinib therapy for a total of 7.5 months until developing an L1196Q gatekeeper mutation. The second patient, whose tumor contained an fusion, continues to benefit from entrectinib after 9 months of therapy.

CONCLUSIONS

RTK fusions in colorectal cancer are a rare, but important disease subgroup that occurs in and wild-type tumors. Despite enrichment in acquired MMR-D tumors, RTK fusions also occur in MSS colorectal cancer and provide an important therapeutic target.