50
IASLC ATLAS OF ALK TESTING IN LUNG CANCER
has been developed in which ALK copy number and ALK protein expression are evaluated in the same cells (Ventana Medical Systems, Inc.) (Nitta 2013), and the method has demonstrated greater sensitivity than conventional IHC, providing more accurate assessment of ALK status. However, the assay is technically difficult. Further validation of this technology is ongoing.
Table 7. Comparison of CISH with with Other Methods of ALK Testing
CISH Study Kim et al., 2011 Yoshida et al., 2011a Assay Kit ALK dual-color break-apart CISH ALK dual-color break-apart CISH No. of Specimens
(% of ALK+)
FISH Criteria for Positivity Not stated
IHC
RT-PCR
Sensitivity Specificity Sensitivity Specificity Sensitivity Specificity
431 (4%)
94%
100%
66.7%
100%
NA
NA
45 (31%)
?20% cells with split signals ?15% cells with split signals
100%
100%
93%
100%
93%
100%
Schildhaus ZytoDot 2C SPEC 100 (16%) et al., 2013 ALK break-apart probe
100%
100%
NA
NA
NA
NA
The assay kit used in the studies by Kim et al. and Yoshida et al. is a product of Ventana Medical Systems, Inc. The kit used in the study by Schildhaus et al. is a product of ZytoVision GmbH. NA = not available.
Examples of Diagnostic Algorithms for ALK Testing
Based on the advantages and characteristics of individual methods for detecting ALK, several investigator groups have proposed diagnostic algorithms for conducting ALK testing (Figures 1-6) (Japanese Lung Cancer Society 2011, Kim 2011, Paik 2011, Thunnissen 2012b, Conklin 2013, Marchetti 2013).
Figure 1. Algorithm proposed by the Japanese Lung Cancer Society, with screening by IHC and confirmation by FISH; RT-PCR is used for cytology specimens. Dotted lines represent possible duplicate examination according to clinicopathologic features. Dotted lines indicate possible duplicated examination according to clinicopathologic features. Modified, with permission from, Biomarker Committee, Japanese Lung Cancer Society. Guidance for ALK Gene Testing in Lung Cancer Patients. Version 1.0 August 1, 2011. Available at http://www. haigan.gr.jp/uploads/photos/641.pdf.
Lung Cancer Samples
Cytology samples, frozen
RT-PCR IHC
Negative Positive
Negative
Positive
FISH
Negative (rare)
Positive
ALK [?X?]???