Department of Gastroenterological Surgery, Tokyo Women's Medical University, 8-1 Kawadacho, Shinjuku-ku, Tokyo, Japan.
Int J Clin Oncol. 2014 Feb;19(1):113-20. doi: 10.1007/s10147-012-0507-4. Epub 2013 Jan 9.
KRAS mutation is widely accepted as a strong, negative predictive marker for anti-epidermal growth factor receptor antibodies, including cetuximab and panitumumab. Previous reports demonstrated approximately 100 % concordance of KRAS status between primary colorectal cancer and liver metastases; however, mismatched KRAS status still occurs.
KRAS status was evaluated in 105 pairs of formalin-fixed primary colorectal cancer and corresponding liver metastases specimens by direct sequencing. DNA quality of patients displaying mismatched KRAS status between primary tumors and metastases was assessed using a Bioanalyzer.
KRAS status was successfully analyzed in 90/105 patients (85.7 %). The concordance rate between primary tumors and metastases was 88.2 % in synchronous metastases (n = 76) and 100 % in metachronous metastases (n = 14). Discordance in KRAS status was observed in nine patients. Independent method validation revealed only five samples showed the same KRAS status between the two methods. DNA quality assessment by a Bioanalyzer revealed that the median length of DNA samples in the peak concentration of the mismatched group was significantly shorter than those in the control group (153.5 vs 276.5 bp, P = 0.0059). In addition, the median value of the percentage of degraded DNA (0-200 bp) in each sample in the mismatched group was significantly higher than the control group (35.5 vs 22 %, P = 0.020). These data suggest that the discordant results for these nine patients (18 samples) were due to low quality DNA, which may obscure polymerase chain reaction analysis, affecting sequencing reliability.
Quality control and assurance of KRAS genotyping is critical, and standardization of the methodology is warranted.
KRAS 突变被广泛认为是抗表皮生长因子受体抗体（包括西妥昔单抗和帕尼单抗）的强阴性预测标志物。先前的报告表明，原发结直肠癌和肝转移灶之间 KRAS 状态的一致性约为 100%；然而，仍然存在 KRAS 状态不匹配的情况。
通过直接测序，评估 105 对福尔马林固定的原发结直肠癌和相应肝转移灶标本的 KRAS 状态。对于原发灶和转移灶之间 KRAS 状态不匹配的患者，使用 Bioanalyzer 评估 DNA 质量。
成功分析了 90/105 例患者（85.7%）的 KRAS 状态。在同步转移（n=76）中，原发灶和转移灶之间的一致性率为 88.2%，在异时转移（n=14）中为 100%。在 9 例患者中观察到 KRAS 状态不一致。独立方法验证显示，两种方法仅在 5 个样本中显示相同的 KRAS 状态。通过 Bioanalyzer 进行的 DNA 质量评估显示，在不匹配组中峰浓度的 DNA 样本的中位数长度明显短于对照组（153.5 与 276.5 bp，P=0.0059）。此外，不匹配组中每个样本中降解 DNA（0-200 bp）的中位数百分比明显高于对照组（35.5 与 22%，P=0.020）。这些数据表明，这 9 例患者（18 个样本）的不一致结果是由于 DNA 质量低，这可能会掩盖聚合酶链反应分析，影响测序的可靠性。
KRAS 基因分型的质量控制和保证至关重要，有必要对方法进行标准化。
