F34 - Retrospective observational analysis of bevacizumab (BV) plus paclitaxel (TXL) as first line treatment in metastatic HER2 negative breast cancer (BC): are BV long responders a different subgroup?

Abstract

Bevacizumab (BV) + paclitaxel (TXL) represents a standard of care in HER2-negative metastatic breast cancer (mBC). Some patients (pts) particularly benefit from this treatment, even if no predictive factor of efficacy is known at the moment. From 2009 we identified 115 MBC pts who received TXL + BV as first line treatment at our institution (schedule: TXL 90mg/mq on days 1,8,15; BV 10 mg/kg on days 1, 15 q28w). Among them we analyzed data of 26 pts (23%), who reported a PFS longer than 18 months (mos). We collected patient demographics, tumor characteristics, initial clinical stage, all type of treatment received. Median age: 48 years (range 34-60). Hystology: ductal carcinoma 23 (89%), lobular carcinoma 2 (7%), mucinous 1 (4%); molecular subtype: luminal A 4 (15%), luminal B 20 (79%, of which 4 cases with progesterone receptor negative), triple negative 2 (6%). Stage at the first diagnosis: 5 stage I, 4 stage II, 8 stage III, 7 stage IV. Most of pts received chemotherapy in the neoadjuvant/adjuvant setting (2 and 14 pts respectively), 10 of them were treated with a taxane-based regimen. Before starting TXL + BV 19 pts (73%) showed a visceral disease, 7 pts (27%) showed a non-visceral disease. 25 pts receveid TXL + BV as initial treatment for mBC, only 1 patient was previously treated with hormonal therapy. Pts received a median number of 7.7 cycles of TXL + BV (range 6-14). 23 pts (88%) received hormonal therapy in association with Bevacizumab as maintenance therapy. An objective response rate (ORR) of 84.7% was reached in the whole population (4 CR, 18 PR). The median follow up was 37.9 mos (range 19-76); median PFS was 30.3 mos (range 22-42), median OS was 40.0 mos (range 23.3-79.7); PR as best response was related with an higher mPFS (32.5 mos), than RC (25.6 mos) or SD (25.3 mos). No difference in mPFS was noticed in pts previously treated with taxane regimes in neo/adjuvant setting (29.7 mos). Our real-world study showed that almost a quarter of pts treated with TXL + BV reached a mPFS longer than expected, with an higher rate of objective responses, regardless of a previous treatment with taxanes in neo/adjuvant setting. Almost all of our pts received TXL + BV as a first approach for metastatic disease, suggesting that this subgroup may particularly benefit from an early antiangiogenic therapy. Translational researches could help us to identify this population before starting treatment.