Gao Xin, Sholl Lynette M, Nishino Mizuki, Heng Jennifer C, Jänne Pasi A, Oxnard Geoffrey R
*Brigham and Women's Hospital, Boston, Massachusetts; and †Dana-Farber Cancer Institute, Boston, Massachusetts.
J Thorac Oncol. 2015 Nov;10(11):1648-52. doi: 10.1097/JTO.0000000000000665.
Break-apart fluorescence in situ hybridization (FISH) is the FDA-approved assay for detecting anaplastic lymphoma kinase (ALK) rearrangements in non-small-cell lung cancer (NSCLC), identifying patients who can gain dramatic benefit from ALK kinase inhibitors. Assay interpretation can be technically challenging, and either splitting of the 5' and 3' probes or loss of the 5' probe constitute rearrangement. We hypothesized that there may be clinical differences depending on rearrangement pattern on FISH.
An IRB-approved database of NSCLC patients at Dana-Farber Cancer Institute was queried for ALK rearrangement. Clinical characteristics and response to crizotinib were reviewed. Immunohistochemistry (IHC) and targeted next-generation sequencing (NGS) were obtained when available.
Of 1614 NSCLC patients with ALK testing, 82 patients (5.1%) had ALK rearrangement by FISH: 30 patients with split signals, 25 patients with 5' deletion, and 27 patients with details unavailable. Patients with 5' deletion were older (p = 0.01) and tended to have more extensive smoking histories (p = 0.08). IHC was positive for ALK rearrangement in all 27 patients with FISH split signals, whereas three of 21 patients with FISH 5' deletion had negative IHC (p = 0.05). Targeted NGS on two of three cases with discordant FISH and IHC results did not identify ALK rearrangement, instead finding driver mutations in EGFR and KRAS. Patients with 5' deletion treated with crizotinib had a smaller magnitude of tumor response (p = 0.03).
Patients with 5' deletion on ALK FISH harbor features less typical of ALK-rearranged tumors, potentially indicating that some cases with this variant are false positives. Corroborative testing with IHC or NGS may be beneficial.
断裂荧光原位杂交（FISH）是美国食品药品监督管理局（FDA）批准的用于检测非小细胞肺癌（NSCLC）中间变性淋巴瘤激酶（ALK）重排的检测方法，可识别出能从ALK激酶抑制剂中显著获益的患者。检测结果的解读在技术上具有挑战性，5'和3'探针的分裂或5'探针的缺失均构成重排。我们推测，根据FISH上的重排模式可能存在临床差异。
查询了达纳-法伯癌症研究所经机构审查委员会（IRB）批准的NSCLC患者数据库，以获取ALK重排情况。回顾了临床特征及对克唑替尼的反应。如有可用数据，则获取免疫组织化学（IHC）和靶向二代测序（NGS）结果。
在1614例接受ALK检测的NSCLC患者中，82例（5.1%）通过FISH检测发现ALK重排：30例信号分裂，25例5'缺失，27例具体情况不详。5'缺失的患者年龄较大（p = 0.01），且往往有更广泛的吸烟史（p = 0.08）。在所有27例FISH信号分裂的患者中，IHC检测ALK重排均为阳性，而在21例FISH 5'缺失的患者中，有3例IHC检测为阴性（p = 0.05）。在3例FISH和IHC结果不一致的病例中，有2例进行的靶向NGS未发现ALK重排，而是在表皮生长因子受体（EGFR）和 Kirsten 大鼠肉瘤病毒癌基因同源物（KRAS）中发现了驱动突变。接受克唑替尼治疗的5'缺失患者的肿瘤反应程度较小（p = 0.03）。
ALK FISH检测显示5'缺失的患者具有一些不太典型的ALK重排肿瘤特征，这可能表明部分具有这种变异的病例为假阳性。采用IHC或NGS进行确证检测可能会有帮助。
