In:
Journal of Clinical Oncology, American Society of Clinical Oncology (ASCO), Vol. 35, No. 15_suppl ( 2017-05-20), p. 11509-11509
Abstract:
11509 Background: RAS mutational status is required to prescribe anti-EGFR antibodies in mCRC. In comparison to molecular testing from tumor tissue, the characterization of RAS mutations in ctDNA is a promising and credible way to shorten the workflow. This study reports for the first time the performance of plasma testing in a large prospective series. Methods: Blood samples were prospectively collected before 1 st line chemotherapy in mCRC patients. ctDNA was centrally assessed by NGS using the colon lung cancer V2 Ampliseq panel and by methylation digital PCR assay (WIF or NPY). Tumor tissue testing was done according to routine practice in each center. We expect a minimal kappa coefficient of 0.7 to reflect concordance. In order to have a precision of ± 0.07 with an estimated 5% of non-exploitable data 425 pts had to be included. Results were analyzed separately in the whole study population and in the subgroup of pts with ctDNA evidenced either by the presence of at least 1 mutation or by the presence of 1 methylated biomarker. Results: From 07/2015 to 12/2016, 425 patients were included, and 406 plasma samples were available for analysis. A RAS mutation was detected in 183 plasma samples (45.1%) As compared to tumor mutational status the kappa coefficient was 0.68 (95%CI: 0.61-0.75) with a concordance of 83.7%. Primary tumor removal, metachronous status, absence of liver metastases and peritoneal carcinomatosis were significantly associated with mutant RAS tumor and negative plasma status. In the subgroup of 324 samples for which ctDNA was evidenced, kappa coefficient was 0.85 (95%CI: 0.80-0.91) with a concordance of 92.9%. 23 pts had discordant results: RAS mutation in tumor tissue and not in ctDNA (15 pts, 4.6%), RAS mutation detected in ctDNA but not in tumor tissue (8 pts, 2.5%). Rectal tumor, absence of liver metastases, peritoneal carcinomatosis and tumor tissue cellularity 〈 10% were associated with discordant cases. Conclusions: We confirm, in this large prospective multicenter study, the high concordance rate for RAS status assessment between blood and tumor samples. This result argues for the use of blood testing in daily practice for pts with detectable ctDNA. Clinical trial information: NCT02502656.
Type of Medium:
Online Resource
ISSN:
0732-183X
,
1527-7755
DOI:
10.1200/JCO.2017.35.15_suppl.11509
Language:
English
Publisher:
American Society of Clinical Oncology (ASCO)
Publication Date:
2017
detail.hit.zdb_id:
2005181-5
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