“Clinicians should order mutational tests for the RAS and BRAF genes and deficient–mismatch repair status testing in patients with colorectal cancer to guide cancer therapy and for identification of patients at high risk for Lynch syndrome….”— Antonia R. Sepulveda, MD, PhD, and colleagues
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As reported in the Journal of Clinical Oncology by Antonia R. Sepulveda, MD, PhD, of Columbia University, and colleagues, a joint guideline on the use of molecular biomarkers for evaluation of colorectal cancer has been developed by an expert panel from the American Society for Clinical Pathology (ASCP), the College of American Pathologists (CAP), the Association for Molecular Pathology (AMP), and ASCO.1 The guideline was informed by data derived from a comprehensive literature search including over 4,000 articles. The panel was co-chaired by Dr. Sepulveda (AMP); Stanley R. Hamilton, MD, PhD (CAP), of The University of Texas MD Anderson Cancer Center; Carmen Allegra, MD (ASCO), of the University of Florida Medical Center, Gainesville; and Wayne Grody, MD, PhD (ASCP), of UCLA Medical Center. The guideline is intended to help establish standard molecular biomarker testing, and guide targeted therapies.
The guideline consists of 21 guideline statements, including 8 recommendations, 10 expert consensus opinions, and 3 no recommendations. The type of statement, strength of evidence, and quality of evidence are shown in brackets.
Guideline Statements
1. Colorectal cancer patients being considered for antiepidermal growth factor receptor (EGFR) therapy must receive RAS mutational testing. Mutational analysis should include KRAS and NRAS codons 12, 13 of exon 2; 59, 61 of exon 3; and 117 and 146 of exon 4 (“expanded” or “extended” RAS). [Type: recommendation; strength of evidence: convincing/adequate, benefits outweigh harms; quality of evidence: high/intermediate)
2a. BRAF p.V600 (BRAF c. 1799 (p.V600) mutational analysis should be performed in colorectal cancer tissue in patients with colorectal cancer for prognostic stratification. [Type: recommendation; strength of evidence: adequate/inadequate, balance of benefits and harms; quality of evidence: intermediate/low]
2b. BRAF p.V600 mutational analysis should be performed in deficient mismatch repair tumors with loss of MLH1 to evaluate for Lynch syndrome risk. The presence of a BRAF mutation strongly favors a sporadic pathogenesis. The absence of a BRAF mutation does not exclude risk of Lynch syndrome. [Type: recommendation; strength of evidence: adequate/inadequate, balance of benefits and harms; quality of evidence: intermediate/low]
3. Clinicians should order deficient–mismatch repair status testing in patients with colorectal cancer for identification of patients at high risk for Lynch syndrome and/or prognostic stratification. [Type: recommendation; strength of evidence: adequate/inadequate, balance of benefits and harms; quality of evidence: intermediate/low]
4. There is insufficient evidence to recommend BRAF c.1799 p.V600 mutational status as a predictive molecular biomarker for response to anti-EGFR inhibitors. [Type: no recommendation; strength of evidence: insufficient, benefits/harms balance unknown; quality of evidence: insufficient]
5. There is insufficient evidence to recommend PIK3CA mutational analysis of colorectal cancer tissue for therapy selection outside of a clinical trial. [Type: no recommendation; strength of evidence: insufficient, benefits/harms balance unknown; quality of evidence: insufficient]
Note: Retrospective studies have suggested improved survival with postoperative aspirin use in patients whose colorectal cancer harbors a PIK3CA mutation.
STRENGTH OF EVIDENCE
Convincing: Two or more level 1 or 2 studies;* one level 1 or 2 study that reported generalizable results. Adequate: Two or more level 1 or 2 studies that lacked the appropriate number and distribution of challenges or were consistent but not generalizable. Inadequate: Combinations of level 1 or 2 studies with unexplained inconsistencies or combinations of one or more level 3 or 4 studies, or expert opinion. *Level 1 studies include systematic reviews of level 2 studies. Level 2 studies include randomized clinical trials of good quality. Levels 3 and 4 are lower quality studies. Source: EGAPP Working Group (Evaluation of Genomic Applications in Practice and Prevention): Genet Med 11(1):3–14, 2009.6. There is insufficient evidence to recommend PTEN analysis (expression by immunohistochemistry [IHC] or deletion by fluorescence in situ hybridization [FISH]) in colorectal cancer tissue for patients who are being considered for therapy selection outside of a clinical trial. [Type: no recommendation; strength of evidence: insufficient, benefits/harms balance unknown; quality of evidence: insufficient]
7. Metastatic or recurrent colorectal cancer tissues are the preferred specimens for treatment-predictive biomarker testing and should be used if such specimens are available and adequate. In their absence, primary tumor tissue is an acceptable alternative and should be used. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
8. Formalin-fixed paraffin-embedded tissue is an acceptable specimen for molecular biomarker mutational testing in colorectal carcinoma. Use of other specimens (eg, cytology specimens) will require additional adequate validation, as would any changes in tissue-processing protocols. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
9. Laboratories must use validated colorectal cancer molecular biomarker testing methods with sufficient performance characteristics for the intended clinical use. Molecular biomarker testing validation should follow accepted standards for clinical molecular diagnostics tests. [Type: strong recommendation; strength of evidence: convincing/adequate, benefits outweigh harms; quality of evidence: high/intermediate]
10. Performance of molecular biomarker testing must be validated in accordance with best laboratory practices. [Type: strong recommendation; strength of evidence: convincing/adequate, benefits outweigh harms; quality of evidence: high/intermediate]
11. Laboratories must validate the performance of IHC testing for molecular biomarkers (currently IHC testing for MLH1, MSH2, MSH6, and PMS2) in accordance with best laboratory practices. [Type: strong recommendation; strength of evidence: convincing/adequate, benefits outweigh harms; quality of evidence: high/intermediate]
12. 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. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
13. Molecular and IHC biomarker testing should be initiated in a timely fashion based upon the clinical scenario and in accordance with institutionally accepted practices. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
Note: Test ordering can occur on a case-by-case basis or by policies established by the medical staff.
14. Laboratories should establish policies to ensure efficient allocation and utilization of tissue for molecular testing, particularly in small specimens. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
15. Members of the patient’s medical team, including pathologists, may initiate molecular biomarker test orders in accordance with institutionally accepted practices. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
16. Laboratories that require send out of tests for treatment predictive biomarkers should process and send specimens to reference molecular laboratories in a timely manner. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
Note: It is suggested that a benchmark of 90% of specimens should be sent out within 3 working days.
17. 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. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
18. Laboratories should use molecular biomarker testing methods that are able to detect mutations in specimens with at least 5% mutant allele frequency, taking into account the analytic sensitivity of the assay (limit of detection) and tumor enrichment (eg, microdissection). [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
Note: It is recommended that the operational minimal neoplastic carcinoma cell content tested be set at least two times the assay’s limit of detection.
19. Molecular biomarker results should be made available as promptly as feasible to inform therapeutic decision-making, both prognostic and predictive. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
Note: It is suggested that a benchmark of 90% of reports be available within 10 working days from the date of receipt in the molecular diagnostics laboratory.
20. 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. [Type: expert consensus opinion; strength of evidence: inadequate/insufficient, benefits and harms in balance; quality of evidence: low]
21. Laboratories must incorporate molecular biomarker testing methods into their overall laboratory quality improvement program, establishing appropriate quality improvement monitors as needed to assure consistent performance in all steps of the testing and reporting process. In particular, laboratories performing colorectal cancer molecular biomarker testing must participate in formal proficiency testing programs, if available, or an alternative proficiency assurance activity. [Type: strong recommendation; strength of evidence: convincing/adequate, benefits outweigh harms; quality of evidence: high/intermediate] ■
DISCLOSURE: For full disclosures of the study authors, visit jco.ascopubs.org.
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