Identification of major factors associated with failed clinical molecular oncology testing performed by next generation sequencing (NGS)

•The variables associated with failed molecular oncology testing by NGS are examined.•Insufficient tissue or DNA account for 90% of failures, independent of test design.•Major failure determinants are biopsy site and procedure type.•Obtaining biopsies of sufficient size is key to improving NGS test success rate.

PurposeDNA analysis by NGS has become important to direct the clinical care of cancer patients. However, NGS is not successful in all cases, and the factors responsible for test failures have not been systematically evaluated.Materials and methodsA series of 1528 solid and hematolymphoid tumor specimens was tested by an NGS comprehensive cancer panel during 2012–2014. DNA was extracted and 2×101 bp paired-end sequence reads were generated on cancer-related genes utilizing Illumina HiSeq and MiSeq platforms.ResultsTesting was unsuccessful in 343 (22.5%) specimens. The failure was due to insufficient tissue (INST) in 223/343 (65%) cases, insufficient DNA (INS-DNA) in 99/343 (28.9%) cases, and failed library (FL) in 21/343 (6.1%) cases. 87/99 (88%) of the INS-DNA cases had below 10 ng DNA available for testing. Factors associated with INST and INS-DNA failures were site of biopsy (SOB) and type of biopsy (TOB) (both p < 0.0001), and clinical setting of biopsy (CSB, initial diagnosis or recurrence) (p < 0.0001). Factors common to INST and FL were age of specimen (p ≤ 0.006) and tumor viability (p ≤ 0.05). Factors common to INS-DNA and FL were DNA purity and DNA degradation (all p ≤ 0.005). In multivariate analysis, common predictors for INST and INS-DNA included CSB (p = 0.048 and p < 0.0001) and TOB (both p ≤ 0.003), respectively. SOB (p = 0.004) and number of cores (p = 0.001) were specific for INS-DNA, whereas TOB and DNA degradation were associated with FL (p = 0.04 and 0.02, respectively).ConclusionsPre-analytical causes (INST and INS-DNA) accounted for about 90% of all failed cases; independent of test design. Clinical setting; site and type of biopsy; and number of cores used for testing all correlated with failure. Accounting for these factors at the time of tissue biopsy acquisition could improve the analytic success rate.

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