Rare GCC2-ALK fusion G13:A20 detected by next generation sequencing in non-small cell lung cancer patients and treatment response

Therapeutic Advances of Rare ALK Fusions in Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancer cases and is the leading cause of cancer-related death. Despite advances in chemotherapy and immunotherapy, the prognosis for advanced patients remains poor. The discovery of oncogenic driver mutations, such as anaplastic lymphoma kinase (ALK) mutations, means that a subset of patients has opportunities for targeted therapy. With the improvement of genetic testing coverage, more and more ALK fusion subtypes and ALK partners have been discovered, and more than 90 rare ALK fusion subtypes have been found in NSCLC. However, unlike the common fusion, echinoderm microtubule-associated protein-like 4 (EML4)-ALK, some rare ALK fusions such as striatin (STRN)-ALK and huntingtin interacting protein 1 (HIP1)-ALK, etc., the large-scale clinical data related to its efficacy are still immature. The clinical application of ALK-tyrosine kinase inhibitors (ALK-TKIs) mainly depends on the positivity of the ALK gene, regardless of the molecular characteristics of the fusion partner. Recent clinical studies in the ALK-positive NSCLC population have demonstrated differences in progression-free survival (PFS) among patients based on different ALK fusion subtypes. This article will introduce the biological characteristics of ALK fusion kinase and common detection methods of ALK fusion and focus on summarizing the differential responses of several rare ALK fusions to ALK-TKIs, and propose corresponding treatment strategies, so as to better guide the application of ALK-TKIs in rare ALK fusion population.

Case Report: Efficacy of ensartinib treatment in pulmonary inflammatory myofibroblastic tumor with a rare GCC2-ALK fusion

Background

Inflammatory myofibroblastic tumors (IMTs) are rare with distal metastasis. Approximately 50% of patients have anaplastic lymphoma kinase (ALK) fusion. Patients with non-small cell lung cancer with ALK fusion are usually highly sensitive to ALK tyrosine kinase inhibitors (TKIs), but the application of TKI in IMT needs further exploration.

Case presentation

A 66-year-old man was diagnosed with IMT with bone metastasis, cT4N0M1c, IVB stage. Immunohistochemistry results showed that he was ALK positive, and next-generation sequencing revealed GCC2-ALK fusion in the IMT. The patient was administered first-line ensartinib 225-mg QD, which targeted GCC2-ALK fusion, and denosumab 120-mg Q4w anti-bone metastasis therapy. The patient developed a grade III rash, and the ensartinib dose was reduced to 125 mg QD; consequently, he achieved a partial response (PR), and the side effects significantly reduced. Computed tomography results showed that the patient maintained PR after 7 months of follow-up, and he was still in a state of progression-free survival without obvious side effects after 11 months of follow-up.

Conclusion

To our knowledge, this is the first case of the GCC2-ALK fusion type in IMT and the first report showing that the use of ensartinib as a TKI in IMT has clinical benefits.