ASCO/CAP HER2 guidelines update

Caterina MarchiòUniversity of Turin

Pathology Unit, FPO-IRCCS Candiolo

Outline

• The evolution of HER2 scoring recommendationsby ASCO/CAP

• Changes in the 2018 focused update: criticaldiscussion step by step

• The future of HER2 evaluation in breast cancer

TO AVOID FALSE POSITIVE

TO AVOID FALSE NEGATIVE

TO ANSWER SPECIFIC CLINICAL QUESTIONS

- Review of pre-analytical and analytical steps

- Rising the thresholdsfor positive results(30% cut-off, HER2/CEP17>2.2)

- Sensitivity raher thanspecificity => thresholds lowered

- ISH algorithm => HER2/CEP17 ratio and HER2 copy number

- Integration of 2013 guidelines (i.e. “focusedupdate”)

- Score 2+ definition- “ISH Groups 2, 3, 4”

by Press et al. 2016

2007 2013 2018

Les fils rouges of ASCO/CAP recommendations

5 Clinical questions addressed

Clinical question 1

What is the most appropriate definition for IHC 2+ (IHC equivocal)?

2018 ASCO/CAP recommendations

Score 2+ definition in 2013

=> “Invasive breast cancer showing“circumferential membrane staining that isincomplete and/or weak/moderate and within > 10% of tumor cells or complete and circumferential membrane staining that isintense and within < 10% of tumor cells.”

Score 2+ definition

2018 ASCO/CAP recommendations

Unusual Score 2+ staining patterns

Baso-lateral membrane staining

Unusual Score 2+ staining patterns

Complete intense membrane staining in < 10% of tumor cells

What to do?

• Test all available blocks (including the LND mets if any)

=> if still <10%: report the percentage of HER2 positive cells

Useful information for any retesting in case of relapse or metastatic disease

Impact of intra-tumor heterogeneity:the neoadjuvant setting

CORE BIOPSY

CORE BIOPSY

CORE BIOPSY

CORE BIOPSY

CORE BIOPSY

CORE BIOPSY

CORE BIOPSY

CORE BIOPSY

Impact of intra-tumor heterogeneity:the neoadjuvant setting

pCR rates

Impact of intra-tumor heterogeneity:the neoadjuvant setting

CORE BIOPSY

CORE BIOPSY

CORE BIOPSY

CORE BIOPSY

Impact of HER2 heterogeneity on anti-HER2 treatment

Clinical question 2

Must HER2 testing be repeated on a surgicalspecimen if initially negative on core biopsy?

2018 ASCO/CAP recommendations

HER2 repeat following a negative result on core biopsy

➢ Integration of core biopsy and surgical specimen info (importance of accurate clinical info)

➢ Preanalytical phase control

Clinical questions 3, 4, 5

Unusal ISH patterns

2018 ASCO/CAP recommendations

2018 ASCO/CAP recommendations

FISH Groups according to Press M et al, J Clin Oncol 2016

BMC Cancer 2014

HER2CEP17

BMC Cancer 2014

Chr17

HER2CEP17

=> Complex patterns of Chr 17 geneticrearrangement in breast carcinomas

J Pathol 2009

Rare

More frequent

2018 ASCO/CAP recommendations

FISH Groups according to Press M et al, J Clin Oncol 2016

2018 ASCO/CAP recommendations

FISH Groups according to Press M et al, J Clin Oncol 2016

Additional work-up means …

• Perform IHC/ review IHC (also on additional blocks)

– Report acc. to IHC score

• If score 2+ confirmed:

– Count additional cells (additional observer)

Discordant scoring: resultadjudicated per internal

procedures

Concordant scoring

ISH

AMPNOT Amp

HER2 POSITIVEHER2 negative

SCORE 0 SCORE 1+ SCORE 2+ SCORE 3+

EQUIV

B. Bradfield D. J. Slamon

NEJM 2001

In HER2+ patients

San Antonio Breast Cancer Symposium, December 5-9, 2017

Population of “HER2-low” breast cancer patientsScore 1+/2+ not amp (HER2/CEP17 <2 and HER2 copy number < 4)

Molecular subtyping by PAM50

Luminal B in the large majority (76%)HER2 mRNA levels much closer to HER2-negHER2-enriched in 5% of cases

Marchiò C et al, Am J Surg Pathol 2018

N=45

HER2-directed ADC in clinical development

Pernas S & Tolaney S, Therapeutic Advances in Medical Oncology 2019

What’s next?

ISH

AMPNOT Amp

HER2 POSITIVEHER2 negative

SCORE 0 SCORE 1+ SCORE 2+ SCORE 3+

EQUIV

ISH

AMPNOT Amp

HER2 negative

SCORE 0 SCORE 1+ SCORE 2+ SCORE 3+

EQUIV

“HER2 low” HER2 POSITIVE

Acknowledgements

Breast Unit IRCCS CandioloAnna SapinoFilippo MontemurroRiccardo Ponzone

Giuseppe VialePatrizia Dell’Orto

IHCIvana SarottoFISHLaura CasorzoPatologia MolecolareTiziana Venesio

Research LabLaura Annaratone, Enrico Berrino, Erica PeanoChiara Piccinelli

Traguardi di Eccellenza nelle Scienze mediche Esplorando le Omiche

Anne Vincent-Salomon

FrédériquePenault-Llorca