Randomized multicenter trial of 3 weekly cabazitaxel versus weekly paclitaxel chemotherapy in the first-line treatment of HER2 negative metastatic breast cancer (MBC).

Abstract

1008 Background: Paclitaxel is commonly used as first line chemotherapy for HER2 negative MBC. However, with response rates of 21.5-53.7% and a significant risk of peripheral neuropathy there is a need for more effective and better tolerated chemotherapy (CCT). Methods: This open label randomised (1:1) phase 2 trial compared 6 cycles of cabazitaxel (25 mg/m2) every 3 weeks, with weekly paclitaxel (80mg/m2) over 18 weeks as first line CCT. HER2 negative and performance status ≤1 patients were eligible. Patients on cabazitaxel received GCSF prophylaxis. Primary endpoint was Progression Free Survival (PFS) with 127 events required to detect a hazard ratio (HR) of 0.65 with 85% power. Secondary endpoints included objective response rate (ORR; RECIST 1.1), time to response (TTR), overall survival (OS), safety and tolerability and quality of life (QoL). Results: 158 patients were recruited from 14 UK hospitals (79 in each arm). Median age (range) was 56(34-81) in the cabazitaxel arm and 61(34-79) in the paclitaxel arm. 61% of patients were performance status 0. Median time on treatment was 15 weeks for both arms, but more patients on paclitaxel had a treatment delay (61% vs 39%) or dose reduction (37% vs 24%). Comparing cabazitaxel to paclitaxel after 146 PFS events, median PFS was 6.7 vs 5.8 months (HR 0.84; 95%CI 0.60–1.18, P = 0.3). There was no difference in OS, median 19.3 vs 20.0 months (HR 0.94; 95%CI 0.63-1.40, P = 0.7), ORR (42% vs 37%) or TTR (HR 1.09; 95%CI 0.68–1.74, P = 0.7). Grade ≥3 adverse events occurred in 42% of patients on cabazitaxel and 48% on paclitaxel. Diarrhoea, febrile neutropenia and nausea were the most common grade ≥3 events in the cabazitaxel arm with rates of 11%, 11% and 10% respectively compared to 1%, 1% and 0% in the paclitaxel arm. In the paclitaxel arm the top grade ≥3 events were lung infection and peripheral neuropathy, 6% and 5% respectively compared to 2.5% and 0% in the cabazitaxel arm. Peripheral neuropathy of any grade was reported by 55% of patients treated with paclitaxel vs 17% on cabazitaxel. Alopecia occurred in 41% of patients on paclitaxel compared to 27% on cabazitaxel. Adverse events leading to discontinuation were more frequent with paclitaxel (22%) than cabazitaxel (14%). Over the course of treatment, mean EQ5D single index utility score (+0.05; 95%CI 0.004-0.09, P = 0.03) and visual analogue scale score (+7.7; 95%CI 3.1-12.3, P = 0.001) were higher in the cabazitaxel arm compared to paclitaxel suggestive of better QoL on Cabazitaxel. Conclusions: 3 weekly cabazitaxel as first line chemotherapy in HER2 negative MBC does not significantly improve PFS compared to weekly paclitaxel, though it has a lower risk of peripheral neuropathy with better patient reported overall health outcomes. Cabazitaxel is safe and well tolerated for MBC and requires fewer hospital visits, an important consideration in the COVID pandemic and beyond. Clinical trial information: NCT03048942 .