Potential unreliability of ALK variant allele frequency in the efficacy prediction of targeted therapy in NSCLC / 医学前沿

Anaplastic lymphoma kinase (ALK) is the most common fusion gene involved in non-small cell lung cancer (NSCLC), and remarkable response has been achieved with the use of ALK tyrosine kinase inhibitors (ALK-TKIs). However, the clinical efficacy is highly variable. Pre-existing intratumoral heterogeneity (ITH) has been proven to contribute to the poor treatment response and the resistance to targeted therapies. In this work, we investigated whether the variant allele frequencies (VAFs) of ALK fusions can help assess ITH and predict targeted therapy efficacy. Through the application of next-generation sequencing (NGS), 7.2% (326/4548) of patients were detected to be ALK positive. On the basis of the adjusted VAF (adjVAF, VAF normalization for tumor purity) of four different threshold values (adjVAF < 50%, 40%, 30%, or 20%), the association of ALK subclonality with crizotinib efficacy was assessed. Nonetheless, no statistical association was observed between median progression-free survival (PFS) and ALK subclonality assessed by adjVAF, and a poor correlation of adjVAF with PFS was found among the 85 patients who received first-line crizotinib. Results suggest that the ALK VAF determined by hybrid capture-based NGS is probably unreliable for ITH assessment and targeted therapy efficacy prediction in NSCLC.

A non-small cell lung carcinoma patient responded to crizotinib therapy after alectinib-induced interstitial lung disease / 浙江大学学报·医学版

A 54-year-old, non-smoking woman was diagnosed as stage ⅣB adenocarcinoma with widespread bone metastasis (cT4N2M1c) in the First Affiliated Hospital, Zhejiang University School of Medicine. Immunohistochemistry result showed the presence of anaplastic lymphoma kinase (ALK) gene rearrangement; next-generation sequencing (NGS) indicated EML4-ALK fusion (E6:A20) with concurrent CCDC148-ALK (C1:A20), PKDCC-ALK (Pintergenic:A20)and VIT-ALK (V15:A20) fusions. After 32 weeks of alectinib treatment, the patient complained cough and exertional chest distress but had no sign of infection. Computed tomography (CT) showed bilateral diffuse ground glass opacities, suggesting a diagnosis of alectinib-related interstitial lung disease (ILD). Following corticosteroid treatment and discontinuation of alectinib, clinical presentations and CT scan gradually improved, but the primary lung lesions enlarged during the regular follow-up. The administration of crizotinib was then initiated and the disease was stable for 25 months without recurrence of primary lung lesions and ILD.