[267] Modified Mandard Tumour Regression Grade Predicts Residual Cancer Burden Score in Neoadjuvant Treated Breast Cancer

Ciara Ryan, Jessica White, Fionnuala O'Connell, Tara Jane Browne, Linda Feeley, Michael W Bennett. Cork University Hospital, Cork, NA, Ireland

Background: Evaluation of pathologic response to neoadjuvant treatment in breast cancer is an important prognostic factor, however, criteria for its classification have not been standardized. The Residual Cancer Burden (RCB) system is frequently used and combines several histologic parameters, including nodal status, into a complex logarithmic equation (RCB=1.4(finvdprim)0.17+[4(1-0.75)LN)dmet]0.17) yielding four categories - pathologic complete response (pCR) and RCB scores 1-3 - which correlate with distant relapse-free survival (0-36% at 5 yrs). The Mandard Tumour Regression Grade (TRG) is a simple, easily applied qualitative comparison of relative proportion of tumour bed residual carcinoma and fibrosis. It is frequently applied in gastrointestinal cancers, but its use has not been studied in breast cancer.
Design: We aim to
1) Compare Mandard TRG to RCB
2) Modify Mandard TRG to incorporate nodal status
3) Compare modified system to validated RCB score in the same cohort
Fifty consecutive neoadjuvant-treated breast cancer cases (2011-12) were classified using the Mandard TRG. This system was then modified to incorporate nodal status. The same cases were also classified into RCB categories using the online calculator. Two pathologists classified each case.
Results: Mandard TRGs and RCB classes are compared in Table 1.

Mandard TRG and Equivalent RCB Class
 RCB Class
Mandard TRGpCR123
1 - Complete regression101*00
2 - Isolated cell nests038*2*
3 - More residual cancer but fibrosis > tumour0016*
4 - Residual cancer > fibrosis0016*
5 - No regression0001
* positive lymph nodes

Applying the simple rule - to predict RCB class, increase the Mandard TRG by one when there is lymph node positivity - accurately stratifies 43/50 cases by RCB class. Collapsing those RCB classes with minimal (pCR and RCB1; 0%) versus significant (RCB2-3; 22-36%) 5-year recurrence risk, the modified Mandard TRG accurately stratifies 100% of cases into clinically relevant prognostic categories (Table 2).

Risk Stratification by Modified Mandard TRG
Recurrence RiskRCB ClassMandard TRG+/- LNMODIFIED Mandard TRG
Minimal (0%)pCR11
 RCB 11 + LN2
Significant (22-36%)RCB 22 + LN3
 RCB 32 + LN (>10)3
  3 + LN4
  4 + LN5
  5 + LN5

Conclusions: A modified Mandard TRG, incorporating lymph node status is rapid, reproducible, easily applicable and clinically relevant in determing response to neoadjuvant treatment in breast cancer. Employing one simple rule, this system reliably separates cases into validated RCB classes offering a viable alternative for evaluating pathologic response in routine practice.
Category: Breast

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 24, Wednesday Morning


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