Everolimus with paclitaxel plus bevacizumab as first-line therapy for HER2-negative metastatic breast cancer (MBC): A randomized, double-blind, placebo-controlled phase II trial of the Sarah Cannon Research Institute (SCRI).

Abstract

1018 Background: Constitutive activation of mTOR and amplified PI3K/Akt/mTOR signaling are common in MBC, and increase as treatment-resistance is acquired. Everolimus (E), an mTOR inhibitor, has single agent activity, combines well with paclitaxel (P) and bevacizumab (B), and prolonged PFS when added to AI therapy in BOLERO-2. In this randomized phase II trial, E was added to P/B as first-line treatment of HER2-negative MBC. Methods: Women with untreated HER2-negative MBC were randomized (1:1) to P 90mg/m2 IV (days 1, 8, and 15) and B10mg/kg IV (days 1 and 15) q28 days with E 10mg PO (Arm 1) or placebo PO (Arm 2) daily. Response assessment was performed q8 weeks until progression or intolerable toxicity. Primary endpoint was PFS. Secondary endpoints: safety, overall response rate, response duration, overall survival. 110 pts allowed detection of improvement in median PFS from 11 to 16 months with 70% power. Results: Between 8/2009 and 6/2011, 112 pts were randomized (Arm 1=55; Arm 2=57). Median age: 58 years (range: 25-79). 88% were ER+ or PR+. Pts received a median 5 treatment cycles (range: <1- 26+); 18 (16%) pts remain on treatment (Arm1, 9; Arm 2, 9). Median PFS were 8.8 months (Arm 1) and 7.1 months (Arm 2) (95% CIs 7.4-9.6; 5.5-9.1 months, p=0.79, HR 0.94). Complete responses were observed in 5% [Arm1, 4 (7%); Arm 2, 2 (4%)] with partial responses in 49% [Arm1, 29 (53%); Arm 2, 26 (46%)]. Responses rates in taxane pretreated pts Arm 1 22%, Arm 2 12%. Hematologic toxicity was similar in both arms; grade 3 mucositis occurred in 13% of E pts. Dose reductions (47% vs 25%) and interruptions (42% vs 26%) were more frequent with E due to mucositis and rash. Treatment discontinuation rates were similar. Conclusions: The addition of E did not result in a significant improvement in the efficacy of weekly paclitaxel/bevacizumab in the first-line treatment of HER2-negative MBC although response rates and median PFS were better with E. Possible explanation for these results may include lower dose intensity in the E arm, treatment of less resistant pts, or intrinsic differences in E activity when added to antiestrogen vs chemotherapy.