[195] Basal Marker Reactivity in Triple Negative Breast Carcinomas Does Not Predict Pathologic Complete Response Following Neoadjuvant Chemotherapy.

James A Kraus, Sushil Beriwal, David J Dabbs, Rohit Bhargava. Magee-Womens Hospital of UPMC, Pittsburgh, PA

Background: Neoadjuvant chemotherapy (NACT) has assumed an increasingly prominent role in the management of breast cancer. Pathologic complete response (pCR) following NACT is most commonly achieved in hormone receptor negative breast carcinomas, including “triple negative” and “ERBB2” tumors. The objective of this study is to assess the value of “basal-like” immunohistochemical (IHC) markers in predicting pCR following NACT in triple negative breast carcinomas.
Design: From 2008 to 2010, consecutive cases of triple negative breast carcinoma treated with NACT were identified in the pathology database at our institution. Sixty-three of these cases had at least one basal marker IHC result. Percent tumor volume reduction following NACT and IHC results for CK5 (or CK5/6), CK14, CK17 and EGFR were obtained from pathology reports. Any reactivity was considered a positive result as per the British Columbia group criteria. pCR was defined as absence of invasive carcinoma in the breast and regional lymph nodes following NACT.
Results: The overall rate of pCR was 28% (28 of 101). Eighty-nine percent (17 of 19) of tumors with pCR were positive for CK5 (compared to ninety percent [36 of 40] of those without pCR; p = 1.00).

CK5 Status with respect to pCR

	CK5 Positive	CK5 Negative	Total
Tumors with pCR	4	39	43
Tumors without pCR	2	18	20
Total	6	57	63

p = 1.000

Similarly, eighty-five percent (17 of 20) of tumors with pCR were positive for EGFR (compared to ninety-two percent [35 of 38] of those without pCR; p = 0.4055).

EGFR Status with respect to pCR

	EGFR Positive	EGFR Negative	Total
Tumors with pCR	3	35	38
Tumors without pCR	3	17	20
Total	6	52	58

p = 0.405

The reactivity for CK14 and CK17 was also not predictive of pCR (p values of 1.0 and 0.485 respectively). Percent tumor volume reduction (TVR) was significantly higher in CK5 negative cases (93.8% compared to 65.9% TVR in CK5 positive tumors; p = 0.006), but showed no association with the other basal markers. All triple negative tumors in this study were positive for at least one of the basal IHC markers tested.
Conclusions: Basal marker reactivity in triple negative breast carcinomas does not predict pathologic complete response following neoadjuvant chemotherapy. Although the CK5 negative tumors were associated with higher percent tumor volume reduction in this study, a larger data set should be examined for confirmation. Other basal markers showed no significant association with TVR. The role of "basal phenotype" IHC markers in diagnostic pathology should be carefully re-assessed.
Category: Breast

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 31, Monday Morning