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NTRK Fusion Landscape in 195 Positive Cases of 17 Tumors: A Chinese Multicenter Retrospective Study With Optimized
Shafei Wu1, Jian Wang2, Wentao Yang2
1Peking Union Medical College Hospital, Beijing, China.
Abstract:
Neurotrophic tyrosine receptor kinase (NTRK) fusions are crucial in tumorigenesis and in guiding targeted therapy with TRK inhibitors. However, their rarity, fusion heterogeneity, and limitations of conventional pan-TRK immunohistochemistry (IHC) impede accurate clinical detection. This multicenter retrospective study analyzed 374 next-generation sequencing/fluorescence in situ hybridization-validated samples (195 NTRK positive and 179 NTRK negative) collected from 12 Chinese centers to investigate fusion heterogeneity and refine the interpretation of pan-TRK IHC. We developed an amplification protocol by combining the traditional pan-TRK IHC (EPR17341) with the OptiView Amplification Kit and established new interpretation criteria. A total of 40 solid tumor types were included, and 23 unique fusion partners were identified. Papillary thyroid cancer was the most common NTRK-positive tumor (49.74%) and harbored all 3 NTRK subtypes. Among NTRK-positive samples, NTRK3 (74.87%) was the most prevalent subtype, followed by NTRK1 (23.59%). ETS variant transcription factor 6 (ETV6) was the most frequent fusion partner identified in 122 of 195 cases. It was uniquely shared across all 3 NTRK subtypes, with its fusion to NTRK1 being reported for the first time. NTRK1 and NTRK3 exhibited marked fusion partner specificity, with no overlap in their associated partners except for ETV6. The optimized pan-TRK IHC protocol significantly improved staining efficiency by enhancing intensity and clarity. Consequently, the newly established criteria (cytoplasmic intensity ≥1 in ≥50% of tumor cells or any nuclear intensity ≥1) exhibited outstanding detection performance, achieving an overall sensitivity of 94.36% and increasing specificity to 79.89% compared with 60.22% under the conventional protocol. Particularly, the detection sensitivity for NTRK3 fusions was significantly enhanced and reached 95.89%. This study contributes to clarifying NTRK fusion distribution in patients and validates a standardized, sensitive pan-TRK IHC strategy for clinical screening.
Insights
This study refined pan-TRK immunohistochemistry (IHC) for detecting neurotrophic tyrosine receptor kinase (NTRK) fusions in solid tumors. An optimized protocol and new criteria significantly improved detection sensitivity and specificity for NTRK fusions.
Area of Science:
- Oncology
- Molecular Diagnostics
- Cancer Biomarkers
Background:
- Neurotrophic tyrosine receptor kinase (NTRK) fusions are key drivers in tumorigenesis and targets for TRK inhibitor therapy.
- Accurate clinical detection of NTRK fusions is challenged by their rarity, heterogeneity, and limitations of conventional pan-TRK immunohistochemistry (IHC).
- Understanding NTRK fusion heterogeneity is crucial for developing effective targeted therapies.
Purpose of the Study:
- To investigate NTRK fusion heterogeneity across diverse solid tumors.
- To refine the interpretation of pan-TRK IHC for improved clinical detection of NTRK fusions.
- To develop and validate an optimized pan-TRK IHC protocol and new interpretation criteria.
Main Methods:
- Multicenter retrospective analysis of 374 NGS/FISH-validated solid tumor samples.
- Development of an amplified pan-TRK IHC protocol using EPR17341 and the OptiView Amplification kit.
- Establishment of new interpretation criteria for pan-TRK IHC and validation against conventional methods.
Main Results:
- Identified 23 unique fusion partners across 40 solid tumor types, with papillary thyroid cancer being the most common NTRK-positive tumor.
- NTRK3 (74.87%) was the most prevalent subtype, followed by NTRK1 (23.59%), with ETV6 as the most frequent fusion partner across subtypes.
- The optimized pan-TRK IHC protocol with new criteria achieved 94.36% sensitivity and 79.89% specificity, significantly improving upon conventional methods (60.22% sensitivity).
Conclusions:
- The study clarifies the distribution of NTRK fusions in a large cohort of Chinese patients.
- An optimized pan-TRK IHC strategy with new interpretation criteria offers a standardized and sensitive approach for clinical screening of NTRK fusions.
- This improved diagnostic approach can facilitate targeted therapy selection for patients with NTRK fusion-positive cancers.
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