Department of Pathology, GROW-School for Oncology and Reproduction, Maastricht University Medical Center, MUMC+ Maastricht, Netherlands & Department of Pathology, Erasmus Medical Center, Rotterdam, Netherlands.
ETOP IBCSG Partners Foundation, ETOP Statistical Center, Frontier Science Foundation-Hellas & National and Kapodistrian University of Athens, Athens, Greece.
Lung Cancer. 2024 Aug;194:107860. doi: 10.1016/j.lungcan.2024.107860. Epub 2024 Jun 26.
ROS1 fusion is a relatively low prevalence (0.6-2.0%) but targetable driver in lung adenocarcinoma (LUAD). Robust and low-cost tests, such as immunohistochemistry (IHC), are desirable to screen for patients potentially harboring this fusion. The aim was to investigate the prevalence of ROS1 fusions in a clinically annotated European stage I-III LUAD cohort using IHC screening with the in vitro diagnostics (IVD)-marked clone SP384, followed by confirmatory molecular analysis in pre-defined subsets.
Resected LUADs constructed in tissue microarrays, were immunostained for ROS1 expression using SP384 clone in a ready-to-use kit and Ventana immunostainers. After external quality control, analysis was performed by trained pathologists. Staining intensity of at least 2+ (any percentage of tumor cells) was considered IHC positive (ROS1 IHC + ). Subsequently, ROS1 IHC + cases were 1:1:1 matched with IHC0 and IHC1 + cases and subjected to orthogonal ROS1 FISH and RNA-based testing.
The prevalence of positive ROS1 expression (ROS1 IHC + ), defined as IHC 2+/3+, was 4 % (35 of 866 LUADs). Twenty-eight ROS1 IHC + cases were analyzed by FISH/RNA-based testing, with only two harboring a confirmed ROS1 gene fusion, corresponding to a lower limit for the prevalence of ROS1 gene fusion of 0.23 %. They represent a 7 % probability of identifying a fusion among ROS1 IHC + cases. Both confirmed cases were among the only four with sufficient material and H-score ≥ 200, leading to a 50 % probability of identifying a ROS1 gene fusion in cases with an H-score considered strongly positive. All matched ROS1 IHC- (IHC0 and IHC1 + ) cases were also found negative by FISH/RNA-based testing, leading to a 100 % probability of lack of ROS1 fusion for ROS1 IHC- cases.
The prevalence of ROS1 fusion in an LUAD stage I-III European cohort was relatively low. ROS1 IHC using SP384 clone is useful for exclusion of ROS1 gene fusion negative cases.
ROS1 融合是肺腺癌（LUAD）中一种相对低发生率（0.6-2.0%）但可靶向的驱动因素。理想情况下，需要使用免疫组织化学（IHC）等强大且低成本的检测方法来筛选可能携带这种融合的患者。本研究的目的是使用 IVD 标记的 SP384 克隆进行 IHC 筛选，调查在临床注释的欧洲 I-III 期 LUAD 队列中 ROS1 融合的发生率，然后在预定义的亚组中进行确认性分子分析。
使用 SP384 克隆在现成试剂盒和 Ventana 免疫染色仪中对组织微阵列构建的 LUAD 进行 ROS1 表达免疫染色。经过外部质量控制后，由经过培训的病理学家进行分析。至少 2+（任何百分比的肿瘤细胞）的染色强度被认为是 IHC 阳性（ROS1 IHC+）。随后，ROS1 IHC+病例与 IHC0 和 IHC1+病例按 1:1:1 匹配，并进行正交 ROS1 FISH 和基于 RNA 的检测。
ROS1 表达阳性（ROS1 IHC+）的阳性率（定义为 IHC 2+/3+）为 4%（866 例 LUAD 中的 35 例）。对 28 例 ROS1 IHC+病例进行了 FISH/RNA 检测，仅发现 2 例存在确认的 ROS1 基因融合，这对应于 ROS1 基因融合的下限发生率为 0.23%。这意味着在 ROS1 IHC+病例中，识别融合的概率为 7%。在这两个确认的病例中，只有 4 例有足够的材料和 H 评分≥200，导致在 H 评分被认为是强阳性的病例中，ROS1 基因融合的识别概率为 50%。所有匹配的 ROS1 IHC-（IHC0 和 IHC1+）病例也通过 FISH/RNA 检测呈阴性，这导致 ROS1 IHC-病例中缺乏 ROS1 融合的概率为 100%。
在一个 LUAD 分期 I-III 期的欧洲队列中，ROS1 融合的发生率相对较低。使用 SP384 克隆进行 ROS1 IHC 有助于排除 ROS1 基因融合阴性病例。
