Controversies in Breast Pathology ELENA PROVENZANO ADDENBROOKES HOSPITAL, CAMBRIDGE

Controversies in Breast Pathology ELENA PROVENZANO ADDENBROOKES HOSPITAL, CAMBRIDGE

Neoadjuvant Chemotherapy Indications: Management of locally advanced invasive breast cancers including inflammatory breast cancer Down-staging of large inoperable cancers to permit surgical resection Routine management of women with high risk disease who would require adjuvant chemotherapy based on biological tumour characteristics and clinical-radiological findings

Prognostic factors post NACT Size matters Complete pathological response Pre treatment histological grade Post treatment histological grade Residual tumour size Residual tumour cellularity Lymphovascular space invasion Number of lymph nodes containing metastatic carcinoma Size of metastases Evidence of chemotherapy effect in lymph nodes TILs (tumour infiltrating lymphocytes)

Size of residual tumour Component of TNM staging Post treatment TNM stage (6 th edition) associated with outcome Essential component of RCB scoring system RCB score shows a strong association with survival outcomes across all tumour subtypes TNBC ER+/HER2- HER2+

Measuring Size Post NACT Thorough macroscopic (gross) assessment of the specimen critical for accurate classification of pcr and assessment of size post NACT A multidisciplinary approach with adequate clinical information and access to imaging results is essential Close clinical/ radiological correlation to map the precise location of the tumour bed is preferable to exhaustive blind sampling Placement of a marker clip at the time of diagnosis is very helpful in the event of an excellent response to treatment

Measuring Size Post NACT Minimum information required: Clear indication neoadjuvant Rx has been given Location of tumour/s within the breast diagram best Pre treatment size on imaging Post treatment size and whether there has been any response

Patterns of tumour response A. Concentric shrinking

Measuring size post NACT Concentric shrinking pattern single residual focus Measure size of residual invasive cancer Do not include tumour bed extending beyond invasive focus

Measuring size post NACT

B. Scatter pattern Patterns of tumour response

Measuring size post NACT Scatter pattern of response multiple islands of tumour cells spread across tumour bed What do you measure? Total extent of disease including all foci Size of largest single focus

Measuring size post NACT Tumour size often more difficult to assess after neoadjuvant treatment. If there is a single lesion present on pre-treatment imaging, then treat residual disease as a single tumour, especially if tumour cells are present within a reactive stromal background consistent with a solitary tumour bed (A). The combination of size and residual tumour cellularity is the best indicator of response. Provenzano et al., Mod Path 2015.

Measuring size post NACT BUT (A) is the size measurement recommended in the RCPath guidelines (A) is the size measurement used to calculate the RCB 7 th and 8 th edition AJCC TNM largest contiguous area of tumour cells (B) and use (m) modifier to indicate multifocal disease No current published evidence that shows a relationship between (B) and survival outcomes

Significance of nodal disease Nodal status post chemotherapy a strong predictor of outcome von Minckwitz G et al. JCO 2012;30:1796-1804

Significance of nodal disease Hennessy et al., J Clin Oncol 2005;23:9304-11 403 pts proven node pos 22% axillary pcr, 69% also pcr breast Axillary conversion the MOST significant predictor of OS Size of residual breast tumour NOT predictive if residual nodal disease No influence of size of metastasis prognosis still worse if < 0.1 mm Evidence of nodal response associated with improved DFS

Significance of nodal disease Cure et al., Breast Ca Res Treatment 2002;76(1):37-45 277 pts, tumours > 3 cm 39% clinically node pos -> ypn0 Number of positive nodes post chemo strongest predictor of survival Klauber DeMore et al., Ann Surg Oncol 2006;13:685-91 122 pts, 52% node positive pre chemo Worse DFS/ OS with increased number of nodes and increasing size of metastasis Size of largest metastasis the strongest predictor of survival on multivariate analysis ITC s regarded as node positive

ITC s post chemotherapy Presence of isolated tumour cells in lymph nodes TNM call ypn0(i) BUT not pcr WHO/ RCPath call node positive i.e. NOT pcr do NOT regard as pcr nodal equivalent of minimal residual disease often background fibrosis indicating previous macrometastatic disease with regression measure size of entire deposit including intervening fibrosis**

ypn post NACT New definition in 8 th edition TNM introduced beginning 2018 Size of the largest contiguous focus of residual tumour in the node Any treatment associated fibrosis should NOT be included A description of number of foci present and total distance over which they extend may be helpful for clinicians to determine extent of residual disease Deposit 0.2 mm is ypt0(i+); NOT regarded as pcr This is NOT the measurement of size of metastasis used in the RCB, which is the largest deposit INCLUDING associated treatment related fibrosis No evidence in literature associating nodal status measured in this way with survival

ypn post chemotherapy

Case study 55 yo female. Inflammatory breast cancer. Neoadjuvant chemotherapy on NeotAnGo trial. Post treatment mastectomy and axillary clearance.

Case study 30 mm residual invasive lobular carcinoma Partial response to neoadjuvant chemotherapy 7/11 nodes with metastatic carcinoma in the form of scattered single cells within background fibrosis

Case Study

How do you report nodal status in this case? A. Measure excluding fibrosis = ITCs - Negative [ypn0(i+)] but not pcr = yptnm B. Measure entire deposit including fibrosis - Positive [ypn2] and not pcr = RCPath/ RCB Would you recommend regional nodal irradiation for this patient

Take Home Points Changes in the way size of tumour and metastases measured in latest TNM Size measurement used for TNM not the same as size measurement used for RCB or recommended way of measuring size in RCPath guidelines

HER2 status Rakha et al., J Clin Path 2014

HER2 status 3+ 2+

Current ISH Guidelines Definitely Positive Uncommon groups with uncertainty as to clinical significance Definitely Negative

HER2 FISH

HER2 FISH polysomy Sapino et al., Frontiers in Onc 2013 Multiple green and orange signals True polysomy of chr 17 is very rare Usual scenario is coamplification of both CEP17 and HER2 loci

HER2 FISH CEP 17 monosomy Only one green signal due to loss of the CEP17 site

What does this mean clinically? BCIRG Meta-analysis Press et al., JCO 2016;34:3518-28. Review of pooled data from BCIRG trials Group 1: 20% 0/1+, 30% 2+, 50% 3+ Group 2: 91% 0/1+, 9% 2+, 0% 3+ Group 3: 77% 0/1+, 11% 2+, 11% 3+ Group 4: 94% 0/1+, 5% 2+, 1% 3+ Group 5: 99% 0/1+, 0.5% 2+, 0.05% 3+

BCIRG Meta-analysis

BCIRG Meta-analysis Press et al., JCO 2016;34:3518-28.

Review of ISH Guidelines Clarify interpretation of ISH to reduce variation Require concomitant review of IHC AND ISH to arrive at diagnosis Avoid routine use of alternative chr17 probes Literature sparse Variable results depending on probe used Introduction of statistical error due to multiple testing

HER2 Guidelines Focused update (unpublished) Reflex ISH for IHC 2+ Call HER2 negative if low absolute HER2 copy number Ratio >2, HER2 < 4 Ratio < 2, copy number 4-6 (= current UK guidelines) Call HER2 positive if ratio > 2, HER2 4-6 Call HER2 positive if Ratio < 2, HER2 6 Heterogeneous group Recent data shows some but not all patients respond to HER2 targeted therapy

HER2 Guidelines Focused update (unpublished) Updated guidelines still unpublished Recommendation is to continue to use 2013 guidelines NHS BSP Pathology Co-Ordinating Committee is undertaking a UK based review of these cases prior to adopting the ASCO CAP Update once it is published My reports add a comment This tumour has an elevated HER2:CEP17 ratio due to relative loss of the CEP 17 locus without an increase in HER2 copy number. Whilst regarded as HER2 positive under current guidelines, this subgroup did not show a benefit from HER2 targeted therapies in the BCIRG analysis.

HER2 Status Are all HER2 +ve cancers the same? Retrospective analysis of NOAH study looking at PAM50 subtypes Only 55% of HER2+ tumours HER2-E subtype; 21% luminal, 7% basal-like, 18% normal-like Better pcr rates in HER2-E vs luminal HER2+ tumours (53% v 29%) with larger improvement in EFS with addition of Trastuzumab Prat et al., Clin Cancer Res 2014;20(2):511-21.

HER2 Status Are all HER2 +ve cancers the same? Predictors of response in HER2 positive cancers In the NEOSPHERE trial, higher levels of HER2 protein expression associated with pcr after dual targeted Rx Bianchini et al., Breast Ca Res 2017;19:16. FISH: higher HER2:CEP17 ratio OR = 2.11, optimum cut off 4.5 higher HER2 copy number OR = 1.15, optimum cut off 14 Wu et al., Oncotargets and Therapy 2018;11:801-8 Higher pcr rate with high level amplification (copy number >10) than low level amplification (6-10) 55% v 24% No difference in RFS or OS Guiu et al., BrJC 2010;103:1335-42.