Eli Lilly and Co, Indianapolis, IN 46285, USA.
Clin Colorectal Cancer. 2013 Sep;12(3):195-203.e2. doi: 10.1016/j.clcc.2013.05.001.
Kirsten rat sarcoma virus (KRAS) wild-type status determined using a locked nucleic acid (LNA)-mediated quantitative polymerase chain reaction (qPCR) clamping assay (LNA assay) predicted response to therapy in the CRYSTAL (Cetuximab Combined With Irinotecan in First-Line Therapy for Metastatic Colorectal Cancer) study. A companion KRAS diagnostic tool has been developed for routine clinical use (QIAGEN therascreen kit) (QIAGEN Manchester Ltd, Manchester, UK). We wanted to assess the concordance between the validated US Food and Drug Administration (FDA)-approved therascreen assay and the LNA assay in determining the KRAS status of a subset of patients enrolled in the CRYSTAL study.
DNA extracted from paraffin-embedded tumor sections was tested for KRAS status using the therascreen assay. Efficacy data from the CRYSTAL study were assessed to determine if the overall survival (OS) hazard ratio for cetuximab in patients identified as having KRAS wild-type status using the therascreen assay was equivalent to that in patients identified as KRAS wild-type using the LNA assay. This was determined by assessing if the concordance between the therascreen assay and the LNA assay met the minimum threshold (prespecified as 0.8) to achieve a significant difference in the OS hazard ratio in favor of the cetuximab + FOLFIRI (5-fluorouracil, leucovorin [folinic acid], irinotecan) arm in the KRAS wild-type population as identified using the therascreen assay.
Of the 148 samples determined to be KRAS wild-type (therascreen assay), 141 (95.3%) samples were also KRAS wild-type (LNA assay) and 7 samples (4.7%) were KRAS mutant (LNA assay). The prespecified primary concordance measure p was 141/148 = 0.953 (95% confidence interval [CI], 0.905-0.981). The concordance was statistically significantly higher than the prespecified threshold of 0.8 for concordance between the therascreen assay and the LNA assay. Consistent with the concordance exceeding the prespecified threshold, the OS hazard ratio (cetuximab + FOLFIRI arm vs. FOLFIRI arm) in the KRAS wild-type population, determined by the therascreen assay, supported a significant benefit for cetuximab (ie, the 95% CI excluded 1) and was comparable to the OS hazard ratio observed in the CRYSTAL study KRAS wild-type population (LNA assay) even after adjustment for potentially confounding baseline variables.
These results support the utility of the therascreen assay for identifying patients who may benefit from cetuximab therapy for metastatic colorectal cancer.
使用锁核酸（LNA）介导的定量聚合酶链反应（qPCR）夹心法（LNA 检测）确定的 Kirsten 大鼠肉瘤病毒（KRAS）野生型状态，可预测CRYSTAL（西妥昔单抗联合伊立替康一线治疗转移性结直肠癌）研究中的治疗反应。已经开发出一种用于常规临床使用的 KRAS 诊断工具（QIAGEN therascreen 试剂盒）（QIAGEN Manchester Ltd，英国曼彻斯特）。我们希望评估在美国食品和药物管理局（FDA）批准的 therascreen 检测和 LNA 检测在确定CRYSTAL 研究入组患者的 KRAS 状态方面的一致性。
使用 therascreen 检测从石蜡包埋肿瘤切片中提取的 DNA 以确定 KRAS 状态。评估 CRYSTAL 研究的疗效数据，以确定使用 therascreen 检测确定为 KRAS 野生型的患者的西妥昔单抗总生存（OS）风险比是否与使用 LNA 检测确定为 KRAS 野生型的患者的 OS 风险比相当。这是通过评估 therascreen 检测和 LNA 检测之间的一致性是否达到了最小阈值（预先指定为 0.8）来确定的，该阈值旨在使使用 therascreen 检测确定为 KRAS 野生型的患者的 OS 风险比有利于西妥昔单抗+FOLFIRI（5-氟尿嘧啶、亚叶酸[甲酰四氢叶酸]、伊立替康）臂。
在确定为 KRAS 野生型（therascreen 检测）的 148 个样本中，141 个（95.3%）样本也是 KRAS 野生型（LNA 检测），7 个样本（4.7%）是 KRAS 突变型（LNA 检测）。预先指定的主要一致性测量 p 为 141/148=0.953（95%置信区间[CI]，0.905-0.981）。一致性显著高于预先指定的 0.8 一致性阈值，用于 therascreen 检测和 LNA 检测之间的一致性。与一致性超过预定阈值一致，使用 therascreen 检测确定的 KRAS 野生型患者的 OS 风险比（西妥昔单抗+FOLFIRI 臂与 FOLFIRI 臂）支持西妥昔单抗的显著获益（即，95%CI 排除 1），并且与 CRYSTAL 研究中 KRAS 野生型患者的 OS 风险比（LNA 检测）相当，即使在调整了潜在混杂的基线变量后也是如此。
这些结果支持 therascreen 检测用于识别可能从西妥昔单抗治疗转移性结直肠癌中获益的患者的效用。
