CastPCR is a newly developed gene analysis assay with high sensitivity and specificity. Multiple studies have demonstrated that CastPCR is superior in gene analysis of tumor tissue compared with other assays such as Sanger sequencing and ARMS. In previous experiments, we have identified the sensitivity of CastPCR in detection of EGFR mutation-known lung cancer cell lines mimicing that of peripheral blood: 0.1% in exon 19 deletion (Del19), L858R in exon 21 and 1% in T790M in exon 20. Since there is difficulty in obtaining tumor tissue from late-staged lung cancer patients and the infeasibility of repeated biopsy and dynamic monitoring during targeted therapy, a complementary method is badly needed.
107 FFPE tissue samples of treatment-naive lung adenocarcinoma patients and matched peripheral blood were collected. CastPCR was used to analysis the EGFR mutation status (exon 19 del2235-2249, del2236-2250, exon 20 T790M and exon 21 L858R) both in the FFPE samples and the peripheral blood. Feasibility-identifying parameters including sensitivity, specificity, positive predictive value, negative predictive value and the concordance was calculated, respectively.
1. In FFPE samples, 51.4% (55/107) were EGFR mutation-positive: 37.4% (40/107) harbored EGFR sensitizing mutations (Del 19 or/and L858R) and 18.7% (20/107) harbored EGFR resistant mutations (T790M), and 5.6% (6/107) harbored double mutations in the same sample. 2. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and the concordance of EGFR mutation detection in cfDNA by CastPCR was shown in the table.rn
Table: 51P Parameters of mutation analysisrn
|Parameters||EGFR||T790M||19Del & L858Rrn|
|Sensitivityrn||56.4% (31/55)rn||45.0% (9/20)rn||57.5% (23/40)rn|
|Specificityrn||94.2% (49/52)rn||100.0% (87/87)rn||95.5% (64/67)rn|
|PPVrn||91.2% (31/34)rn||100.0% (9/9)rn||88.5% (23/26)rn|
|NPVrn||67.1% (49/73)rn||88.8% (87/98)rn||79.0% (64/81)rn|
|Concordancern||74.8% (80/107)rn||89.7% (96/107)rn||81.3% (87/107)rn|
PPV: Positive Predictive Value; NPV: Negative Predictive Valuern
CastPCR can not only effectively detect the EGFR mutation statues in tumor FFPE samples, but also can confer clinical feasibility of EGFR mutation analysis in cfDNA.
Clinical trial indentification
Legal entity responsible for the study
1. the Health Scientific Research Project of Jiangsu Province, Nanjing, China (grant no. H201235); 2. Key Project of Nanjing Medical Science and Technology Development Foundation, Nanjing, China (grant no. ZKX12012).
All authors have declared no conflicts of interest.