ASCO has endorsed the recently developed joint College of American Pathologists (CAP), International Association for the Study of Lung Cancer (IASLC), and Association for Molecular Pathology (AMP) guideline on molecular testing for selection of patients with lung cancer for EGFR and ALK inhibitor treatment.

The endorsement, reported in Journal of Clinical Oncology by Natasha B. Leighl, MD, of Princess Margaret Cancer Centre, Toronto, and colleagues, follows review of the guideline by an ASCO expert panel co-chaired by Dr. Leighl and Natasha Rekhtman, MD, PhD, of Memorial Sloan Kettering Cancer Center, New York.¹ As stated by Dr. Leighl and colleagues, “[The] guideline represents an important advance toward standardization of EGFR and ALK testing practices and is of major clinical relevance in advancing the care of patients with lung cancer.”

The guideline, summarized below, provides CAP/IASLC/AMP expert panel recommendations (evidence grades A and B), consensus opinions (opinions), and suggestions.

Which patients should be tested for EGFR mutations and ALK rearrangements?

Recommendation: EGFR and ALK molecular testing should be used to select patients for EGFR-targeted and ALK-targeted tyrosine kinase inhibitor therapy, and patients with lung adenocarcinoma should not be excluded from testing on the basis of clinical characteristics.

Recommendation: For lung cancer resection specimens, EGFR and ALK testing is recommended for adenocarcinomas and mixed lung cancers with an adenocarcinoma component, regardless of histologic grade. For fully excised lung cancer specimens, EGFR and ALK testing is not recommended in lung cancers that lack any adenocarcinoma component, such as pure squamous cell carcinomas, pure small cell carcinomas, or large cell carcinomas lacking any immunohistochemistry evidence of adenocarcinoma differentiation.

Recommendation: For more-limited lung cancer specimens (biopsies, cytology) in which an adenocarcinoma component cannot be completely excluded, EGFR and ALK testing may be performed in cases that show squamous or small-cell histology, but clinical criteria (eg, younger age, lack of smoking history) may be useful in selecting a subset of these samples for testing.

Recommendation: To determine EGFR and ALK status for initial treatment selection, primary tumors or metastatic lesions are equally suitable for testing.

Opinion: For patients with multiple, apparently separate, primary lung adenocarcinomas, each tumor may be tested, but testing of multiple different areas within a single tumor is not necessary.

When should a patient specimen be tested for EGFR mutation or ALK rearrangement?

Recommendation: EGFR mutation testing should be ordered at the time of diagnosis for patients who present with advanced-stage disease (stage IV) who are suitable for therapy or at time of recurrence or progression in patients who originally presented with lower stage disease but were not previously tested.

Suggestion: ALK rearrangement testing should be ordered at the time of diagnosis for patients who present with advanced-stage disease (stage IV) and are suitable for therapy or at time of recurrence or progression in patients who originally presented with lower stage disease but were not previously tested.

Opinion: EGFR and ALK testing of tumors at diagnosis from patients who present with stage I, II, or III disease is encouraged, but the decision should be made locally by each laboratory in collaboration with its oncology team.

Recommendation: Tissue should be prioritized for EGFR and ALK testing.

How rapidly should test results be available?

Opinion: EGFR and ALK results should be available within 2 weeks (10 working days) of receiving the specimen in the testing laboratory.

Opinion: Laboratories with average turnaround times > 2 weeks need to make available a more rapid test—either in-house or through a reference laboratory—in instances of clinical urgency.

Opinion: Laboratory departments should establish processes to ensure that specimens that have a final histopathologic diagnosis are sent to outside molecular pathology laboratories within 3 working days of receiving requests and to intramural molecular pathology laboratories within 24 hours.

How should specimens be processed for EGFR mutation testing?

Opinion: Formalin-fixed, paraffin-embedded specimens or fresh, frozen, or alcohol-fixed specimens should be used for polymerase chain reaction (PCR)-based EGFR mutation tests.

Other tissue treatments (eg, acidic or heavy metal fixatives, or decalcifying solutions) should be avoided. Cytologic samples are also suitable for EGFR and ALK testing, with cell blocks being preferred over smear preparations.

What are the specimen requirements for EGFR testing?

Opinion: Adequacy of specimens for EGFR testing should be determined by assessing cancer cell content and DNA quantity and quality. Each laboratory should establish the minimum proportion and number of cancer cells needed for mutation detection during validation. A pathologist should assess the tumor content of each specimen and either perform, or guide a trained technologist to perform, microdissection for tumor cell enrichment as needed.

How should EGFR testing be performed?

Recommendation: Laboratories may use any validated EGFR testing method with sufficient performance characteristics.

Opinion: Laboratories should use EGFR test methods that are able to detect mutations in specimens with ≥ 50% cancer cell content, although laboratories are strongly encouraged to use (or have available at an external reference laboratory) more sensitive tests that are able to detect mutations in specimens with as little as 10% cancer cells.

Opinion: Clinical EGFR mutation testing should be able to detect all individual mutations that have been reported with a frequency of ≥ 1% of EGFR-mutated lung adenocarcinomas.

Recommendation: Immunohistochemistry for total EGFR is not recommended for selection of EGFR tyrosine kinase inhibitor therapy. EGFR copy number analysis (ie, fluorescence in situ hybridization [FISH] or chromogenic in situ hybridization) is not recommended for selection of EGFR tyrosine kinase inhibitor therapy.

What is the role of KRAS analysis in selecting patients for targeted therapy with EGFR tyrosine kinase inhibitors?

Recommendation: KRAS mutation testing is not recommended as a sole determinant of EGFR tyrosine kinase inhibitor therapy.

What additional testing considerations are important in the setting of secondary or acquired EGFR tyrosine kinase inhibitor resistance?

Recommendation: Testing on specimens from patients with acquired resistance to EGFR kinase inhibitors should be able to detect the secondary EGFR T790M mutation in as few as 5% of cells.

What methods should be used for ALK testing?

Recommendation: Laboratories should use an ALK FISH assay using dual-labeled break-apart probes for selecting patients for ALK tyrosine kinase inhibitor therapy; ALK immunohistochemistry, if carefully validated, may be considered as a screening methodology to select specimens for ALK FISH testing.

Recommendation: Reverse transcription-PCR is not recommended as an alternative to FISH for selecting patients for ALK inhibitor therapy.

Opinion: A pathologist should be involved in the selection of sections for ALK FISH testing, by assessing tumor architecture, cytology, and specimen quality. A pathologist should participate in the interpretation of ALK FISH slides, either by performing the analysis directly or by reviewing the interpretations of cytogeneticists or technologists with specialized training in solid tumor FISH analysis.

Opinion: Testing for secondary mutations in ALK associated with acquired resistance to ALK inhibitors is not currently required for clinical management.

Are other molecular markers suitable for testing in lung cancer?

Recommendation: Testing for EGFR should be prioritized over other molecular markers in lung adenocarcinoma.

Suggestion: After EGFR testing, testing for ALK should be prioritized over other proposed molecular markers in lung adenocarcinoma, for which published evidence is insufficient to support testing guideline development at the present time.

Must all adenocarcinomas be tested for both EGFR and ALK?

Opinion: Laboratories may implement testing algorithms to enhance the efficiency of molecular testing of lung adenocarcinomas, provided the overall turnaround time requirements are met.

How should EGFR and ALK results be reported?

Opinion: EGFR mutation testing reports and ALK FISH reports should include a results and interpretation section readily understandable by ­oncologists and by nonspecialist ­pathologists.

How should EGFR and ALK testing be validated?

Opinion: EGFR and ALK testing validation should follow the same guidelines as for other molecular diagnostics and FISH tests.

How should quality assurance be maintained?

Opinion: Laboratories should follow similar quality control and quality assurance policies and procedures for EGFR and ALK testing in lung cancers as for other clinical laboratory assays. Laboratories performing EGFR and ALK testing for tyrosine kinase inhibitor therapy should enroll in proficiency testing, if available. ■

Disclosure: Drs. Leighl and Rekhtman reported no potential conflicts of interest. For full disclosures of the authors, visit jco.ascopubs.org.

Reference

1. Leighl NB, Rekhtman N, Biermann WA, et al: Molecular testing for selection of patients with lung cancer for epidermal growth factor receptor and anaplastic lymphoma kinase tyrosine kinase inhibitors: American Society of Clinical Oncology endorsement of the CAP/IASLC/AMP guideline. J Clin Oncol. October 13, 2014 (early release online).