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ALK screen (lung cancer)

Also known as: ALK IHC (lung cancer); ALK FISH (lung cancer)

Test category:

Oncology - Lung cancer

Use of test

Purpose:

Gene fusions involving the ALK gene and other gene partners occur in a subset of non-small cell lung cancers (NSCLC). Such fusions carry implications regarding selection of and response to therapies.

Utility:

The presence of an ALK rearrangement in NSCLC detected by fluorescent in situ hybridisation (FISH) analysis is associated with increased sensitivity to ALK tyrosine kinase inhibitor therapy e.g. with crizotinib.

The ALK FISH test is used as a second-line test in NSCLC following i) a negative EGFR mutation result, and ii) to confirm an ALK rearrangement suggested by ALK over-expression on immunohistochemistry (IHC) studies. Tumours that do not have ALK over-expression on IHC are highly unlikely to have an ALK rearrangement.

Ethical considerations:

This is an assay for non-heritable mutations. It does not raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient.

Methodology:

IHC using an assay designed to detect ALK over-expression in NSCLC samples. If IHC is equivocal or positive, this is followed by FISH analysis, using probes to identify rearrangements resulting in the fusion of ALK with a partner gene. This interphase FISH test has a cut off at 15% as set by the probe manufacturer.

Requesting the test

Ordering:

This test is usually requested by an oncologist or the pathologist providing the initial histopathology report. Please use the specific request form.

Request form:

Download the somatic mutation request form.

Sample required:

The standard ALK screening process involves an initial IHC assay. If this is negative, no further testing will be carried out. If ALK IHC is positive, ALK FISH is recommended to confirm the presence of an ALK rearrangement.

ALK FISH can also be requested separately (regardless of the ALK IHC result). If required, please denote this on the request form.

Formalin-fixed, paraffin embedded tissue (FFPE) in 15 sections of 4 uM thickness, dried overnight at 37°C onto charged/coated slides.

Special instructions:

Please label each slide with patient and block identifiers plus number them sequentially 1-15. Stain slides 1 and 15 with H&E and leave slides 2 to 14 unstained.

The request should be accompanied by the somatic mutation request form (above) and a copy of the original histopathology report.

Turnaround time:

5 business days.

Price:

This test has a Medicare rebate which, subject to the requirements of the Medicare descriptor being met, may cover all or part of the cost.

Rebate:

The Medicare details, including descriptor and schedule fee, are listed under MBS item 73341.