Abstract 16: Landscape and outcome of TRK fusion-positive Cancers

TRK inhibitors achieve marked tumor-agnostic efficacy in TRK fusion-positive cancers and consequently are now an established standard of care. Little is known, however, about the demographics, clinical outcomes, response to alternative standard therapies, or genomic characteristics of TRK fusion-positive cancers. Utilizing a center-wide screening program involving more than 26,000 prospectively sequenced patients, genomic and clinical data from all cases with identified TRK fusions were extracted. An integrated analysis was performed of genomic, therapeutic, and phenomic outcomes. In total, we identified 76 cases with confirmed TRK fusions (0.27% overall prevalence) involving 48 unique rearrangements and 17 distinct cancer types. The presence of a TRK fusion was associated with depletion of concurrent oncogenic drivers (p=4.4E-7) and lower tumor mutation burden (p=4.2E-9), with the exception of colorectal cancer where TRK fusions co-occur with microsatellite instability (MSI-H). Longitudinal profiling in a subset of patients indicated that TRK fusions were present in all sampled timepoints in 82% (14/17) of cases. Progression-free survival on first-line therapy, excluding TRK inhibitors, administered for advanced disease was 9.6 months (95% CI: 4.8-13.2). The best ORR achieved with chemotherapy containing-regimens across all lines of therapy was 63% (95% CI: 41-81). Among 12 patients treated with checkpoint inhibitors, the only response observed was in an MSI-H colorectal patient. TRK fusion-positive cancers can respond to alternative standards of care, although efficacy of immunotherapy in the absence of other predictive biomarkers (MSI-H) appears limited. TRK fusions are present in tumors with simple genomes lacking in concurrent drivers that may partially explain the tumor-agnostic efficacy of TRK inhibitors. Citation Format: Ezra Y. Rosen, Debra A. Goldman, Jaclyn F. Hechtman, Ryma Benayed, Alison M. Schram, Emiliano Cocco, Sophie Shifman, Yixiao Gong, Ritika Kundra, James P. Solomon, Alberto Bardelli, Maurizio Scaltriti, Alexander Drilon, Alexia Iasonos, Barry S. Taylor, David M. Hyman. Landscape and outcome of TRK fusion-positive Cancers [abstract]. In: Proceedings of the AACR Special Conference on Advancing Precision Medicine Drug Development: Incorporation of Real-World Data and Other Novel Strategies; Jan 9-12, 2020; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_1):Abstract nr 16.