Abstract P2-14-01: Breast cancer patients with HER2 low-expression: An under-recognized group at significant risk for recurrence

• Published in: Cancer research (Chicago, Ill.) Vol. 73; no. 24_Supplement; pp. P2 - P2-14-01
• Main Authors: Vreeland, TJ, John, BS, Trappey, AF, Schneble, EJ, Hale, DF, Clifton, GT, Shumway, NM, Perez, SA, Papamichail, M, Ponniah, S, Peoples, GE, Mittendorf, EA
• Format: Journal Article
• Language: English
• Published: 15.12.2013
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.SABCS13-P2-14-01

Abstract Background: HER2 over-expression is associated with more aggressive malignant disease. The introduction of trastuzumab and other HER2-directed therapies, however, has led to improved prognosis for patients (pts) with HER2 over-expressing (OE) tumors. Currently, no HER2-targeted therapies are available for patients with HER2 low-expressing (LE) (1+, 2+ by IHC) tumors. We are conducting a randomized, controlled Phase II trial of multiple peptide vaccines enrolling patients with any level of HER2 expression (1+, 2+ and 3+). Here, we report survival data based on levels of HER2 expression in our unvaccinated, control pts. Methods: After standard of care therapy, disease-free, high-risk BCa pts were randomized to receive either peptide+GM-CSF (Vaccine Group, VG) or GM-CSF alone (Control Group, CG) in six, monthly doses followed by four boosters every six months. Pts were prospectively followed for recurrence. Demographic information was available for all pts and was compared between groups using chi square or fisher exact tests. Disease-Free Survival (DFS) was compared using log rank. Results: To date, we have enrolled 196 pts in the CG. 96 pts had HER2 OE tumors, 100 had LE tumors. The only significant demographic difference between the CG OE and LE groups was more ER/PR positive patients in LE (LE 72% vs OE 51%, p = 0.008). 83% of CG OE pts received trastuzumab, 3% of CG LE pts received trastuzumab. At a median f/u of 30 mo, DFS was significantly higher for CG OE vs CG LE (92.5% v 65.5%, p = 0.001). Conclusions: In the cohort of control pts from our ongoing vaccine trial, conducted in an era when Tz has been standard of care therapy for patients with HER2 OE tumors, we have shown that HER2 LE pts are at higher risk of recurrence than OE pts, despite having more ER/PR positive. This calls for increased efforts to develop novel therapies for patients with HER2 LE disease. We have previously shown a trend towards increased DFS with the HER2 vaccines, AE37 (p = 0.13, median f/u 22 mo) and E75 (p = 0.16, median f/u 60mo) in HER2 LE pts, suggesting that these vaccines may represent one such novel therapeutic approach. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-14-01.