High detection rates of colorectal neoplasia by stool DNA testing with a novel digital melt curve assay.
OBJECTIVE
Current stool DNA tests identify about half of individuals with colorectal cancers and miss most individuals with advanced adenomas. We developed a digital melt curve (DMC) assay to quantify low-abundance mutations in stool samples for detection of colorectal neoplasms and compared this test with other approaches.


METHODS
We combined a melt curve assay with digital polymerase chain reaction and validated the quantitative range. We then evaluated its ability to detect neoplasms in 2 clinical studies. In study I, stool samples from patients with colorectal tumors with known mutations (KRAS, APC, BRAF, TP53) were assayed. In study II, archived stool samples from patients with advanced adenomas containing known KRAS mutations were assayed, along with controls. Results were compared with those from the stool DNA test PreGenPlus (Exact Sciences, Marlborough, MA), Hemoccult, and HemoccultSensa (both Beckman-Coulter, Fullerton, CA).


RESULTS
The DMC assay detected samples in which only 0.1% of target genes were mutated. In study I, the DMC assay detected known mutations in 28 (90%) of 31 tumor samples and 6 (75%) of 8 advanced adenoma samples. In study II, the DMC assay detected 16 (59%) of 27 advanced adenoma samples that contained KRAS mutations, compared with 7% with the Hemoccult, 15% with the HemoccultSensa, and 26% with the PreGenPlus assays (P < .05 for each, compared with the DMC assay); specificities did not differ significantly.


CONCLUSIONS
The DMC assay has a high level of sensitivity in detecting individuals with colon neoplasms and is better than current stool screening methods in detecting those with advanced adenomas. Further studies are indicated.
Zou
Hongzhi
H
Miles and Shirley Fiterman Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota 55905, USA. zou.hongzhi@mayo.edu
Taylor
William R
WR
Harrington
Jonathan J
JJ
Hussain
Fareeda Taher Nazer
FT
Cao
Xiaoming
X
Loprinzi
Charles L
CL
Levine
Theodore R
TR
Rex
Douglas K
DK
Ahnen
Dennis
D
Knigge
Kandice L
KL
Lance
Peter
P
Jiang
Xuan
X
Smith
David I
DI
Ahlquist
David A
DA
D000236:Adenoma / Q000175:diagnosis* / Q000235:genetics*; D000368:Aged; D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics*; D003955:Diagnostic Tests, Routine / Q000379:methods; D005243:Feces; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D009154:Mutation; D009780:Occult Blood; D016133:Polymerase Chain Reaction / Q000379:methods*; D011518:Proto-Oncogene Proteins / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D012680:Sensitivity and Specificity; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D018631:ras Proteins / Q000235:genetics
D004273:DNA, Neoplasm; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins