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Alexander Drilon, MD

Gregory J. Riely, MD, PhD

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Detecting NTRK Gene Fusions in Metastatic Triple-Negative Breast Cancer: Case Report

By: Julia Fiederlein
Posted: Thursday, October 27, 2022

A rare case of metastatic triple-negative secretory breast cancer, which was found to harbor an ETV6::NTRK3 gene fusion on tissue comprehensive profiling—but not on circulating tumor DNA analysis—was described in BMJ Case Reports. According to Gregory Vidal, MD, PhD; Nupur Singh; and colleagues at the University of Tennessee Health Science Center and West Cancer Center and Research Institute, Memphis, and colleagues, this patient profile highlights the importance of careful selection of next-generation sequencing platforms and interpretation of molecular results when making clinical decisions.

“This further supports the use of molecular tumor boards to expedite the determination of key mutations that may impact treatment options,” the investigators remarked. “Molecular profiling for metastatic triple-negative breast cancer should be strongly considered in the first-line metastatic setting to help inform treatment.”

A woman in her mid-40s was diagnosed with invasive ductal carcinoma of the right breast. She experienced ipsilateral chest wall recurrence 6 years after undergoing mastectomy. Approximately 15 years later, the patient presented with almost 4 years of untreated, slowly progressing, triple-negative metastatic breast cancer to the lung.

Comprehensive molecular profiling of a metastatic lesion confirmed a hotspot ETV6::NTRK3 gene fusion, which was not detected on the circulating tumor DNA analysis or molecular profiling performed 4 years prior. A secondary pathologic examination revealed tumor characteristics consistent with secretory breast carcinoma. The patient was treated with the TRK inhibitor larotrectinib, and after 3 months, she achieved a partial response.

“Rapid clinical and radiologic response to larotrectinib therapy shows promise for targeting oncogenic driver mutations based on genetics over immunochemical pathologic subtyping,” the investigators concluded.

Disclosure: The study authors reported no conflicts of interest.


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