According to results recently published at the 2006 annual San Antonio Breast Cancer Symposium, Abraxane® (albumin-bound paclitaxel protein-bound particles for injectable suspension) results in better response rates and progression-free survival-and fewer toxic effects-than Taxotere® (docetaxel) in the initial treatment of metastatic breast cancer.
Paclitaxel is a chemotherapy agent commonly used in the treatment of breast cancer. Abraxane is a newer form of paclitaxel that is bound with albumin, a type of protein normally found in the human body. This form of paclitaxel delivers high concentrations of the active ingredient into the cancer cells and, compared to the original form of the drug, reduces the incidence of side effects.
Researchers recently conducted a randomized Phase II trial to directly compare Abraxane to Taxotere in the initial treatment of metastatic breast cancer. In addition researchers evaluated different doses and schedules of Abraxane.
This trial included over 300 women who had not received prior therapy. Study participants were assigned to one of four treatment groups: 1) Abraxane 300 mg/m2 every three weeks; 2) Abraxane 100 mg/m2 weekly for three weeks out of four; 3) Abraxane 150 mg/m2 weekly for three weeks out of four; 4) Taxotere (100 mg/m2) every three weeks.
- Response rates (the rate of partial or complete disappearance of detectable cancer) were 72% better among patients treated with Abraxane 150 mg/m2 weekly than among patients treated with Taxotere.
- Response rates were 61% better among patients treated with Abraxane 100 mg/m2 weekly than among patients treated with Taxotere.
- Response rates were better among patients who received Abraxane every week than among patients who received Abraxane every three weeks.
- Progression-free survival from all three Abraxane groups was better than in the Taxotere group, although additional follow-up is necessary.
- Grade 4 neutropenia (low white blood cell count) occurred in 74% of patients treated with Taxotere, compared to only 3%–4% of patients treated with weekly Abraxane.
- Febrile neutropenia (neutropenia accompanied by fever) occurred in 7% of patients treated with Taxotere, compared with only 1% of patients treated with Abraxane.
- Grades 1–2 mucositis/stomatitis (sores or inflammation in the mouth) occurred in 20% of patients treated with Taxotere, compared with 3% or less of patients treated with Abraxane.
The researchers concluded that among women with metastatic breast cancer, initial treatment with weekly Abraxane significantly improves response rates compared to treatment with Taxotere and also appears to improve progression-free survival. In addition Abraxane appears to cause fewer toxic effects than Taxotere. Updated results from this Phase II trial will be announced next year, and a Phase III trial comparing Abraxane to Taxotere for initial treatment of metastatic breast cancer is currently being planned.
Reference: Gradishar W, Krasnojon D, Cheporov S, et al. A randomized Phase 2 study of weekly (W) or every-3-week (Q3W) ABI-007 (ABX) versus every-3-week docetaxel as first-line therapy in patients with metastatic breast cancer. Proceedings from the 2006 annual San Antonio Breast Cancer Symposium (SABCS). Oral presentation December 17, 2006. Abstract #46.
Related News: NCCN Adds Abraxane™ to Guidelines for Treatment of Advanced Breast Cancer (12/21/2005)
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