Study of the usefulness of angiotensin type 1 receptor (AGTR1) as a possible response predictor in patients with metastatic breast cancer (mBC) subjected to chemotherapy and treatment with bevacizumab (AVALUZ Study).

Abstract

10608 Background: Angiotensin type 1 receptor (AGTR1) is a membrane receptor implicated in the regulation of arterial pressure. It has also been related to carcinogenesis and tumor spread, and participates in neoangiogenesis. AGTR1 is expressed in a number of neoplasms as BC. In a previous neoadjuvant study, a significant relationship was observed between AGTR1 expression and CR to a regimen of chemo and bevacizumab (B). To study and confirm the relationship between tumor expression of AGTR1 and response to a regimen of chemo and B in pts with mBC. Methods: AGTR1 expression was subjected to immunofluorescence (monoclonal AGTR1 sc1173 antibody, Santa Cruz Biotechnology, CA, USA Dilution 1:50) in 50 samples of mBC pts from the AVALUZ study treated with first line bevacizumab 10 mg/kg, paclitaxel 150 mg/m2 and gemcitabine 2000 mg/m2 d 1 and 15 c/28 d until PD, unacceptable toxicity or medical decision. Immunoreactivity was reported as negative (0), low positive (1+) and high positive (2+). RNA was extracted from paraffin blocks, using the QIAamp DNA FFPE Tissue Kit and Deparaffinization Solution (QIAGEN) and expression of AGTR1 candidate gene was quantified using reverse transcription-PCR (RT-PCR). Results: 60% of the samples expressed AGTR1 (26% weak and 34% intense) – expression being more frequent in HR + tumors (65% vs 45%). Among the 50 samples analyzed, measurable disease was present in 39 pts. Treatment activity was significantly greater in the tumors AGTR1 expression 2+ (p=0.009) (Table). With a median follow-up of 19.30 months, the progression-free interval was longer in the tumors with intense AGTR1 expression (17.7 vs 10.8 months, p=0.132). More consolidated PFS and OS will be presented. Conclusions: AGTR1 expression may be useful as a predictor of response to chemo and bevacizumab. Prospective studies are needed to confirm these findings. [Table: see text]