Colorectal Cancer Molecular Testing Guidelines

· Samples for Testing:

· Prognostic stratification and Lynch syndrome risk (recommendation):

· BRAF c.1799 [p.V600]

· MMR

· Patients with colorectal carcinoma being considered for anti-EGFR therapy (recommendation):

· RAS mutational testing

· Metastatic or recurrent carcinoma tissues preferred, but primary tumour tissue is an acceptable alternative (expert consensus opinion)

· FFPE acceptable, cytology specimens (and other specimen types) will require additional adequate validation (expert consensus opinion)

· Laboratories should establish policies to ensure efficient allocation and utilization of tissue for molecular testing, particularly in small specimens. (expert consensus opinion)

· Members of the patient’s medical team, including pathologists, may initiate colorectal carcinoma molecular biomarker test orders in accordance with institutionally accepted practices. (expert consensus opinion)

· Pathologists must evaluate candidate specimens for biomarker testing to ensure specimen adequacy, taking into account tissue quality, quantity, and malignant tumor cell fraction. Specimen adequacy findings should be documented in the patient report

· Genes, mutations, and Methods:

· KRAS and NRAS mutation (eRAS):

· codons 12 and 13 of exon 2, 59 and 61 of exon 3, and 117 and 146 of exon 4

· BRAF c.1799 [p.V600]

· Insufficient evidence (no recommendation):

· PIK3CA mutation

· PTEN IHC or FISH

· Laboratories should use colorectal carcinoma molecular biomarker testing methods that are able to detect mutations in specimens with at least 5% mutant allele frequency, taking into account the analytical sensitivity of the assay (limit of detection [LOD]) and tumor enrichment (eg, microdissection). (expert consensus opinion)

· Note: It is recommended that the operational minimal neoplastic carcinoma cell content tested should be set at least two times the assay’s LOD.

· Laboratories must use validated colorectal carcinoma molecular biomarker testing methods with sufficient performance characteristics for the intended clinical use. Colorectal carcinoma molecular biomarker testing validation should follow accepted standards for clinical molecular diagnostics tests. (strong recommendation)

· Laboratories must provide clinically appropriate turnaround times and optimal utilization of tissue specimens by using appropriate techniques (eg, multiplexed assays) for clinically relevant molecular and immunohistochemical biomarkers of colorectal cancer. (expert consensus opinion)

· TAT:

· Colorectal carcinoma molecular biomarker results should be made available as promptly as feasible to inform therapeutic decision making, both prognostic and predictive.

· Note: It is suggested that a benchmark of 90% of reports be available within 10 working days from date of receipt in the molecular diagnostics laboratory. (expert consensus opinion)

· Molecular and IHC biomarker testing in colorectal carcinoma should be initiated in a timely fashion based on the clinical scenario and in accordance with institutionally accepted practices (expert consensus opinion)

· Laboratories that require send-out of tests for treatment predictive biomarkers should process and send colorectal carcinoma specimens to reference molecular laboratories in a timely manner

· Benchmark of 90% of specimens sent out within 3 working days of order (expert consensus opinion)

· Reporting:

· BRAF:

· Presence of a BRAF mutation strongly favors a sporadic pathogenesis

· Absence of a BRAF mutation does not exclude risk of Lynch syndrome

· PIK3CA:

· Retrospective studies have suggested improved survival with postoperative aspirin use in patients whose colorectal carcinoma harbors a PIK3CA mutation

· Colorectal carcinoma molecular biomarker testing reports should include a results and interpretation section readily understandable by oncologists and pathologists. Appropriate Human Genome Variation Society and Human Genome Organisation nomenclature must be used in conjunction with any historical genetic designations. (expert consensus opinion)

· Validation:

· Performance of molecular biomarker testing for colorectal carcinoma must be validated in accordance with best laboratory practices. (strong recommendation)

· Ongoing QC/QA:

· Laboratories must incorporate colorectal carcinoma molecular biomarker testing methods into their overall laboratory quality improvement program, establishing appropriate quality improvement monitors as needed to ensure consistent performance in all steps of the testing and reporting process. In particular, laboratories performing colorectal carcinoma molecular biomarker testing must participate in formal proficiency testing programs, if available, or an alternative proficiency assurance activity. (strong recommendation)

References:

· Sepulveda et al. Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline from the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology. Arch Pathol Lab Med 2017;141:625-657. (I have only gone through Table 4: Guideline statements and strengths of recommendations)