Single institution experience with neoadjuvant chemotherapy for metaplastic breast cancer (MBC).

Abstract

1038 Background: Metaplastic breast carcinoma (MBC) is a rare subtype that accounts for <1% of all breast carcinomas. MBC is frequently triple negative and neoadjuvant chemotherapy (NAC) is often used in triple negative breast cancer (TNBC). The objective of this analysis is to ascertain response rates of MBC to NAC as compared to non-metaplastic TNBC. Methods: We searched the Magee Women’s Cancer Center of UPMC IRB-approved neo-adjuvant treatment database which contains outcome data on 594 patients treated from 2004-2010. 116 patients with triple negative breast cancer (ER /PR negative or ER /PR weakly positive (H score of 10 or less) and HER2 negative or indeterminate (HER2 1+ or 2+ without amplification by FISH)), were identified. Nine of these TNBCs had metaplastic subtype and 2 groups were analyzed: metaplastic breast carcinoma (MBC) (N= 9) and non-metaplastic breast carcinoma (NMBC) (N = 107). Tumor volume reduction (TVR), pathologic complete response (pCR), recurrence and mortality were compared in both groups. Results: Mean follow up in MBC group was 43 months and no patients were lost to follow up. Mean tumor size on presentation in MBC group was 4.47 cm while in NMBC group it was 3.33 cm. pCR was noted in 0/9 MBC and 43/107 NMBC cases (p = 0.0253). 6/9 patients had mastectomy, 2/9 had breast conserving surgery (BCS) and 1/9 patients did not have a surgery yet. Average TVR was 28% in MBC cases compared to 74% in NMBCs when cases with pCR were included (p = 0.0001) and 56% when cases with pCR were excluded (p = 0.0202). Follow up on 9 MBC cases revealed 1 recurrence and subsequent death (11%). Follow up on 64 NMBC patients who failed to achieve pCR revealed 22 recurrences (34%) and 18 of them subsequently died (28%).Follow up on 43 NMBC cases that achieved pCR revealed 3 recurrences (7%) and 1 death (2%). Conclusions: MBC was characterized by larger size at baseline as compared to NMBC. There were no pCR’s seen in MBC, but some MBC did achieve response that allowed for breast conservation. Although the average tumor volume reduction was significantly less in MBC compared to NMBC, the NMBC that failed to achieve pCR fared much worse than MBC who did not achieve pCR. Therefore, the triple negative paradox is likely not applicable to MBC.