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P8. Her-2 testing : Impact of 2013 updated ASCO/CAP guidelines on equivocal scoring by IHC and its FISH correlation.

Gurudutt Gupta, Sunil Pasricha, Ritu Garg , Manoj K Panigrahi, Anila Sharma, Jatin S Gandhi, Meenakshi Kamboj, Anurag Mehta

Department of pathology, Rajiv Gandhi Cancer Institute & RC. Rohini Sector 5. Delhi. India.

Introduction: ASCO/CAP guidelines for Her-2 neu testing (2007) were  updated in 2013, with changes in criteria for IHC scoring. It was anticipated that with broadening of the criteria/spectrum for equivocal scoring, it will lead to more equivocal results and subsequent reflex ISH testing.

Material and methods: We compared the incidence of IHC equivocal cases six months before and after the 2013 updated guidelines. Cases reported after adoption of updated guidelines were reclassified into 1+ and 2+ as per 2007 guidelines with FISH correlation.

Results: 228 cases before adoption of the updated guidelines showed equivocal results in 20% cases (46/228). FISH test correlation was available in 34 cases and was amplified in 11 cases (33%).
In comparison,230 cases reported after the adoption of 2013 guidelines, showed equivocal results in 58(25%) cases with FISH test results available in 50 cases.  13/50 were amplified (26%). IHC slides were available for evaluation in 36/58 cases and  9 out of these 36 equivocal cases (25%) were scored 1+ according to 2007 criterion, with negative FISH results in all cases.

Conclusion: Our study revealed an increase in the rate of equivocal cases by IHC and eventually increase (5%) reflex FISH testing as per updated 2013 guidelines with no additional detection of Her-2 amplified case. The increased cost to the patient and laboratory due to reflex FISH testing, is a pitfall. Validation of 2013 guidelines requires larger studies to gauge its utility in identifying additional patients that are eligible for Her-2 directed therapy.

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