基于 RT-qPCR 的 PAM50 乳腺癌分型与标准临床分子标志物的一致性。

BACKGROUND: Many methodologies have been used in research to identify the "intrinsic" subtypes of breast cancer commonly known as Luminal A, Luminal B, HER2-Enriched (HER2-E) and Basal-like. The PAM50 gene set is often used for gene expression-based subtyping; however, surrogate subtyping using panels of immunohistochemical (IHC) markers are still widely used clinically. Discrepancies between these methods may lead to different treatment decisions. METHODS: We used the PAM50 RT-qPCR assay to expression profile 814 tumors from the GEICAM/9906 phase III clinical trial that enrolled women with locally advanced primary invasive breast cancer. All samples were scored at a single site by IHC for estrogen receptor (ER), progesterone receptor (PR), and Her2/neu (HER2) protein expression. Equivocal HER2 cases were confirmed by chromogenic in situ hybridization (CISH). Single gene scores by IHC/CISH were compared with RT-qPCR continuous gene expression values and "intrinsic" subtype assignment by the PAM50. High, medium, and low expression for ESR1, PGR, ERBB2, and proliferation were selected using quartile cut-points from the continuous RT-qPCR data across the PAM50 subtype assignments. RESULTS: ESR1, PGR, and ERBB2 gene expression had high agreement with established binary IHC cut-points (area under the curve (AUC) ≥ 0.9). Estrogen receptor positivity by IHC was strongly associated with Luminal (A and B) subtypes (92%), but only 75% of ER negative tumors were classified into the HER2-E and Basal-like subtypes. Luminal A tumors more frequently expressed PR than Luminal B (94% vs 74%) and Luminal A tumors were less likely to have high proliferation (11% vs 77%). Seventy-seven percent (30/39) of ER-/HER2+ tumors by IHC were classified as the HER2-E subtype. Triple negative tumors were mainly comprised of Basal-like (57%) and HER2-E (30%) subtypes. Single gene scoring for ESR1, PGR, and ERBB2 was more prognostic than the corresponding IHC markers as shown in a multivariate analysis. CONCLUSIONS: The standard immunohistochemical panel for breast cancer (ER, PR, and HER2) does not adequately identify the PAM50 gene expression subtypes. Although there is high agreement between biomarker scoring by protein immunohistochemistry and gene expression, the gene expression determinations for ESR1 and ERBB2 status was more prognostic.

背景：为了识别通常被称为 Luminal A、Luminal B、HER2 富集（HER2-E）和基底样的“内在”乳腺癌亚型，研究中已采用了许多方法。PAM50 基因集常用于基于基因表达的亚分型；然而，免疫组织化学（IHC）标志物面板的替代亚分型在临床上仍广泛使用。这些方法之间的差异可能导致不同的治疗决策。

方法：我们使用 PAM50 RT-qPCR 检测法对 814 例来自 GEICAM/9906 三期临床试验的肿瘤进行了基因表达谱分析，这些肿瘤纳入了局部晚期原发性浸润性乳腺癌的女性。所有样本均在单个部位通过免疫组化（IHC）对雌激素受体（ER）、孕激素受体（PR）和 Her2/neu（HER2）蛋白表达进行评分。HER2 不确定病例通过显色原位杂交（CISH）进行确认。HER2 阳性病例采用免疫组化/CISH 单基因评分与 RT-qPCR 连续基因表达值以及 PAM50 的“内在”亚型分配进行比较。通过从 PAM50 亚型分配的连续 RT-qPCR 数据中使用四分位数切点，选择 ESR1、PGR、ERBB2 和增殖的高、中、低表达。

结果：ESR1、PGR 和 ERBB2 基因表达与既定的 IHC 二分切点具有高度一致性（曲线下面积（AUC）≥0.9）。IHC 检测的雌激素受体阳性与 Luminal（A 和 B）亚型密切相关（92%），但只有 75%的 ER 阴性肿瘤被归入 HER2-E 和基底样亚型。Luminal A 肿瘤比 Luminal B 更常表达 PR（94% vs 74%），而 Luminal A 肿瘤增殖较低（11% vs 77%）。39 例 IHC 检测的 ER-/HER2+肿瘤中有 77%（30/39）被归类为 HER2-E 亚型。三阴性肿瘤主要由基底样（57%）和 HER2-E（30%）亚型组成。多变量分析显示，ESR1、PGR 和 ERBB2 的单基因评分比相应的 IHC 标志物更具预后意义。

结论：乳腺癌的标准免疫组织化学检测面板（ER、PR 和 HER2）不能充分识别 PAM50 基因表达亚型。尽管蛋白免疫组化和基因表达的生物标志物评分之间具有高度一致性，但 ESR1 和 ERBB2 状态的基因表达测定更具预后意义。