Even women with breast cancer whose disease has progressed despite taxane therapy may be able to achieve long-term disease control with a newly developed formulation of paclitaxel.
Data presented at the San Antonio Breast Cancer Symposium found that about one third of women with taxane-refractory metastatic breast cancer achieved objective clinical responses with nanoparticle albumin paclitaxel, called Abraxane, the new formulation that is designed to be at least as effective as paclitaxel but with less toxicity.
“The novel mechanism of action and the current clinical experience indicate that Abraxane, administered either weekly or once every three weeks offers an important new treatment option for patients with advanced breast cancer,” said Joyce O'shaughnessy, MD, Associate Director for Clinical Research, Director of Chemoprevention Research and Co-director of Breast Cancer Research for US Oncology.
Ok'd in January
Abraxane, being developed by American Bioscience Inc., which sponsored the study she presented, was approved by the Food and Drug Administration in January.
“We are looking forward to getting this drug added to our hospital formulary,” said Andrew Seidman, MD, Associate Attending Physician for the Breast Cancer Medicine Service at Memorial Sloan-Kettering Cancer Center.
“Abraxane has been shown to be safe and effective in metastatic breast cancer and can have activity among patients who had been previously taking taxanes.”
In the trial, Dr. O'shaughnessy recruited 106 patients whose breast cancer was progressing on their current regimens that included patients on taxane therapy. Of those, 16 achieved an objective response, and another 16 patients were able to achieve stable disease that was durable through at least 16 weeks, she reported in her poster presentation.
About one third of the women had disease progression while on paclitaxel, about a third on docetaxel, and the others had received both taxanes.
In the open-label Phase II study, patients were administered Abraxane at 125 mg/m2 via 30-minute intravenous infusions weekly for three weeks, followed by one week of rest.
The 28-day cycles were continued until signs of disease progression of biological intolerability. Adult women were eligible for the study if they had confirmed breast cancer with evidence of progression or metastasis. The average age of the participants was 53; most of the women were white, and nearly all were postmenopausal.
Dr. O'shaughnessy said 75% of the women in the study were able to take the full dose of Abraxane. Most patients who had to stop due to toxicity were able to resume treatment at reduced levels.
Abraxane, previously known as ABI-007, is the first biologically interactive composition exploiting a receptor-mediated (gp60) pathway achieving high intracellular tumor concentrations of the active ingredient, paclitaxel.
Phase III studies have shown Abraxane's superiority over paclitaxel in time to progression and response in patients with metastatic breast cancer.
Robert Morgan, Jr., MD, Chief of Adult Neuro-Oncology at City of Hope National Medical Center, commented that the new formulation of paclitaxel might provide an added advantage for the drug, one of the most active treatments for many cancers including breast cancer.
“However, because of paclitaxel's poor solubility in blood, it must be administered dissolved in a substance called Cremophor,” Dr. Morgan explained.
“This agent, though, has substantial toxicity including severe allergic reactions for which pretreatment with powerful steroid medication plus histamine-receptor blockers must be given. Even with these safeguards, allergic reactions continue to occur in a small percentage of patients.”
Fewer Allergic Reactions
In order to prepare safer, more effective formulations of paclitaxel the nanoparticle albumin formulation has been investigated, Dr. Morgan continued.
“This is an advance in the administration of taxanes allowing shorter infusion times and the ability to administer the chemotherapy without the premedications and the attendant potential side effects of the pre-medications.”
The new study from Dr. O'shaughnessy shows that beyond the benefits of allowing safer and more convenient administration of paclitaxel, this formulation is also active in cancers that have become resistant to paclitaxel administered with Cremophor.
“This is perhaps because more of the active chemotherapy drug is able to reach the cancer where it is active,” he said. “This formulation is a definite improvement in an oncologist's ability to treat cancer with one of the most active medications.”
Dr. Seidman said the new formulation, in addition to possibly reducing allergic reactions, might offer a strategic advantage of getting more of the drug to the tumor.
Further studies of Abraxane are warranted, he added, to consider different regimen schedules and possible use of the drug in combination with other treatments.