Assessment of Tumor Sequencing as a Replacement for Lynch Syndrome Screening and Current Molecular Tests for Patients With Colorectal Cancer.

Hampel H1, Pearlman R1, Beightol M2, Zhao W3, Jones D3, Frankel WL3, Goodfellow PJ4, Yilmaz A3, Miller K3, Bacher J3, Jacobson A2, Paskett E1, Shields PG1, Goldberg RM1,5, de la Chapelle A1,6, Shirts BH2, Pritchard CC2; Ohio Colorectal Cancer Prevention Initiative Study Group.

Author information

1: Department of Internal Medicine and the Comprehensive Cancer Center, Ohio State University, Columbus.
2: Department of Laboratory Medicine, University of Washington, Seattle.
3: Department of Pathology, Ohio State University Wexner Medical Center, Columbus.
4: Department of Obstetrics and Gynecology, Ohio State University Wexner Medical Center, Columbus.
5: Department of Internal Medicine, West Virginia University Cancer Institute, Morgantown, West Virginia.
6: Department of Cancer Biology and Genetics, Ohio State University, Columbus.

Abstract

IMPORTANCE:

Universal tumor screening for Lynch syndrome (LS) in colorectal cancer (CRC) is recommended and involves up to 6 sequential tests. Somatic gene testing is performed on stage IV CRCs for treatment determination. The diagnostic workup for patients with CRC could be simplified and improved using a single up-front tumor next-generation sequencing test if it has higher sensitivity and specificity than the current screening protocol.

OBJECTIVE:

To determine whether up-front tumor sequencing (TS) could replace the current multiple sequential test approach for universal tumor screening for LS.

DESIGN, SETTING, AND PARTICIPANTS:

Tumor DNA from 419 consecutive CRC cases undergoing standard universal tumor screening and germline genetic testing when indicated as part of the multicenter, population-based Ohio Colorectal Cancer Prevention Initiative from October 2015 through February 2016 (the prospective cohort) and 46 patients with CRC known to have LS due to a germline mutation in a mismatch repair gene from January 2013 through September 2015 (the validation cohort) underwent blinded TS.

MAIN OUTCOMES AND MEASURES:

Sensitivity of TS compared with microsatellite instability (MSI) testing and immunohistochemical (IHC) staining for the detection of LS.

RESULTS:

In the 465 patients, mean age at diagnosis was 59.9 years (range, 20-96 years), and 241 (51.8%) were female. Tumor sequencing identified all 46 known LS cases from the validation cohort and an additional 12 LS cases from the 419-member prospective cohort. Testing with MSI or IHC, followed by BRAF p.V600E testing missed 5 and 6 cases of LS, respectively. Tumor sequencing alone had better sensitivity (100%; 95% CI, 93.8%-100%) than IHC plus BRAF (89.7%; 95% CI, 78.8%-96.1%; P = .04) and MSI plus BRAF (91.4%; 95% CI, 81.0%-97.1%; P = .07). Tumor sequencing had equal specificity (95.3%; 95% CI, 92.6%-97.2%) to IHC plus BRAF (94.6%; 95% CI, 91.9%-96.6%; P > .99) and MSI plus BRAF (94.8%; 95% CI, 92.2%-96.8%; P = .88). Tumor sequencing identified 284 cases with KRAS, NRAS, or BRAF mutations that could affect therapy for stage IV CRC, avoiding another test. Finally, TS identified 8 patients with germline DPYD mutations that confer toxicity to fluorouracil chemotherapy, which could also be useful for treatment selection.

CONCLUSIONS AND RELEVANCE:

Up-front TS in CRC is simpler and has superior sensitivity to current multitest approaches to LS screening, while simultaneously providing critical information for treatment selection.