P2-18-01: The Magnitude of Trastuzumab Benefit in HER2−Positive (HER2+) Lobular Breast Carcinoma (BC): Results of a HERA Trial Sub-Group Analysis

Autor: G. Viale, Mitchell Dowsett, E Gresko, Otto Metzger, M.J. Piccart, Christos Sotiriou, Marion Procter, R. D. Gelber, Sherene Loi, Brian Leyland-Jones, Azambuja E de
Rok vydání: 2011
Předmět:
Zdroj: Cancer Research. 71:P2-18
ISSN: 1538-7445
0008-5472
DOI: 10.1158/0008-5472.sabcs11-p2-18-01
Popis: Background: Invasive lobular carcinoma (ILC) represents the second most common BC subtype and is often characterized as hormone receptor positive and HER2−negative. However a small subset of ILC is found to be HER2+. Isolated case reports have demonstrated high responsiveness to trastuzumab in patients with advanced HER2+ ILC. The HERA trial compares 1 or 2 years of trastuzumab treatment with observation and 1 versus 2 years of trastuzumab treatment after standard chemotherapy in women with HER2+ breast cancer. We sought to evaluate the incidence of HER2+ ILC and the magnitude of trastuzumab benefit in HER2+ ILC in the context of the HERA trial. In addition, we sought to describe the pattern of hormone receptor positivity in the subsets of ILC and invasive ductal carcinoma (IDC) Methods: The database used in the analysis had a clinical cut-off date of 9th June 2008 and 4-year median follow-up (Gianni et al., 2011). Patients randomized to the 1-year trastuzumab and observation arms were included in the present analysis. Central assessment of hormone receptor status was considered. Histological BC subtype was assessed locally. Results: Of the 1703 women randomized to one-year of trastuzumab and 1698 to observation, 5.5% (n=187) and 94.5% (n=3213) were diagnosed as HER2+ ILC and IDC, respectively. Central hormone receptor status was available in 88.3% (n = 2838) of IDC and 86.1% (n=161) of ILC. ER and/or PR positivity was more common in ILC than IDC (63.4% [102/161] vs. 46.3% [1314/2838]; p Conclusion: HER2+ ILC accounts for 5.5% of patients included in a large population of over 3,000 HER2+ BC. While only a limited number of patients with ILC was enrolled, this analysis suggests an increased ER positivity in ILC compared to IDC. There was no suggestion that patients with HER2+ ILC derived a different magnitude of benefit from adjuvant trastuzumab when compared to the HER2+ IDC cohort. The lack of central pathology review for BC subtype assessment is a caveat of our study. Future research in the field of ILC and particularly in the HER2+ subset should be encouraged. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-18-01.
Databáze: OpenAIRE
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