An audit of frontline (F)ISH testing outside the Australian setting on HER2 positivity rates in breast cancer and the impact of the 2013 ASCO guidelines

Abstract

Aim: To determine our HER2 positivity rates for invasive breast carcinoma using frontline FISH testing rather than CISH or SISH in a laboratory outside Australia, and to understand the impact of the 2013 ASCO guidelines on overall HER2 positivity rates.Data: The HER2 status in patients diagnosed with invasive breast carcinoma between 2009–2014 was determined on core or excision specimens sent to Canterbury Health Laboratories (n=797).Results: HER2 positivity rates varied from 12–21%, with an average of 15.5%. With the introduction of frontline FISH testing, the overall HER2 positivity rate was 13%, below the average for the preceding 4 years of 16%, achieving similar rates for positivity as Bilous et al.1 The 2013 ASCO guidelines resulted in an increase in overall Her2 positivity rates to 20.93%.Discussion: Discussion points will include:•Should New Zealand laboratories adopt the frontline ISH testing model as per College guidelines?•Does frontline ISH testing save money from a whole of systems perspective?•The impact of ASCO guidelines on HER2 positivity rates in breast cancer.•Is it time to change the testing algorithm to an ISH only model?•Suggested guidelines for dealing with equivocal FISH results.•Treatment implications for ISH negative, IHC positive results.•Interesting cases of IHC and FISH discordance.Reference1.Bilous M, Morey AL, Armes JE, et al. Assessing HER2 amplification in breast cancer: findings from the Australian In Situ Hybridisation Program. Breast Cancer Res Treat 2012; 134: 617–24. Aim: To determine our HER2 positivity rates for invasive breast carcinoma using frontline FISH testing rather than CISH or SISH in a laboratory outside Australia, and to understand the impact of the 2013 ASCO guidelines on overall HER2 positivity rates. Data: The HER2 status in patients diagnosed with invasive breast carcinoma between 2009–2014 was determined on core or excision specimens sent to Canterbury Health Laboratories (n=797). Results: HER2 positivity rates varied from 12–21%, with an average of 15.5%. With the introduction of frontline FISH testing, the overall HER2 positivity rate was 13%, below the average for the preceding 4 years of 16%, achieving similar rates for positivity as Bilous et al.1 The 2013 ASCO guidelines resulted in an increase in overall Her2 positivity rates to 20.93%. Discussion: Discussion points will include:•Should New Zealand laboratories adopt the frontline ISH testing model as per College guidelines?•Does frontline ISH testing save money from a whole of systems perspective?•The impact of ASCO guidelines on HER2 positivity rates in breast cancer.•Is it time to change the testing algorithm to an ISH only model?•Suggested guidelines for dealing with equivocal FISH results.•Treatment implications for ISH negative, IHC positive results.•Interesting cases of IHC and FISH discordance. Reference1.Bilous M, Morey AL, Armes JE, et al. Assessing HER2 amplification in breast cancer: findings from the Australian In Situ Hybridisation Program. Breast Cancer Res Treat 2012; 134: 617–24.