Abraxane Better than Taxol for Advanced Breast Cancer
Background and importance of the study:
In January 2005, the U.S. Food and Drug Administration (FDA) approved the chemotherapy drug Abraxane, a new formulation of paclitaxel, for treating advanced (metastatic) breast cancer. The approval is for second-line therapy—after another chemotherapy regimen has been used and has stopped working.
Paclitaxel belongs to a class of chemotherapy drugs called taxanes (Taxol (chemical name: paclitaxel) and Taxotere (chemical name: docetaxel) are the most widely known). Taxanes are powerful drugs that can stop cancer cells from repairing themselves and from making new cells. Studies have shown them to be effective in treating women with advanced breast cancer that does not respond to other forms of chemotherapy. For women with metastatic disease, Taxotere was more effective than Taxol in one of the only comparison studies of the two. Both taxanes are approved by the FDA for women with early-stage disease.
But taxanes cause serious side effects, including low white blood cell counts (neutropenia), weakness, and infection. They also cause extreme skin sensitivity, which can make them difficult to take.
It took many years to design a drug that could safely deliver paclitaxel, the active ingredient in Taxol. Paclitaxel has to dissolve so it can enter the bloodstream. But paclitaxel does not dissolve in water. Up unti now it has been dissolved in Cremophor, a derivative of castor oil. However, Cremophor makes paclitaxel more toxic and more difficult to tolerate. In order to avoid having serious allergic reactions to Cremophor, women must receive steroids before they receive Taxol.
Abraxane provides a new way to make paclitaxel dissolve in water. Instead of Cremophor, Abraxane uses albumin, a natural protein found in the body. A tiny bit of paclitaxel is suspended in each albumin particle. Because albumin is natural to the body, there is no need to take steroids before receiving Abraxane. And since taking Abraxane does not require taking pre-medication to reduce the risk of an allergic reaction, an Abraxane treatment averages 30 minutes compared with three hours for Taxol.
Study design and results: In a Phase III research study, Abraxane was compared directly to Taxol in 454 women. The researchers looked at how the two drugs affected the cancers and the drugs' side effects. They DID NOT look at survival rates.
The women were randomly divided into two groups.
- One group received 260 milligrams of Abraxane over 30 minutes every three weeks.
- The other group received 175 milligrams of Taxol over three hours every three weeks. The women in this group also received the standard steroid pre-medication.
The women in the study had the following characteristics:
- They ranged in age from 33 to 74; most were about 52 years old.
- All had metastatic disease.
- The breast cancer had spread to the liver in about 40% of the women.
- The breast cancer had spread to either the bones or lungs in 33% of the women.
- About 60% of the women in each treatment group had received prior treatment for advanced breast cancer. This means that some of the women in this study were getting Abraxane or Taxol as their first therapy for advanced disease.
- About 50% had been treated with anthracycline, another strong chemotherapy drug.
The results of the study showed that the women who received Abraxane:
- had significantly more cancer shrinkage, also called "overall response rate." Thirty-three percent of the women who received Abraxane had their breast cancer shrink, compared to 19% of the women who received Taxol.
- had no worsening of their breast cancers for an average of 21.9 weeks (about five and a half months), compared to 16.1 weeks (about four months) for women who received Taxol.
- had fewer cases of low white blood cell counts, or neutropenia (34%, compared to 53% of women who received Taxol).
- were MORE likely to have peripheral neuropathy (pain and numbness in the hands and feet) (24 women taking Abraxane, compared with 5 women taking Taxol). When the women stopped the Abraxane treatments, the pain and numbness got better. The women then continued treatment, but received a lower dose of Abraxane (220 milligrams). Early analysis of the neuropathy showed that the pain cleared up more quickly among women taking Abraxane (in about 22 days) than in the women taking Taxol (in about 79 days).
Conclusion and take-home message:
The FDA has approved Abraxane for second-line treatment of advanced breast cancer. The results of a Phase III trial show that cancers responded better to Abraxane than Taxol and stayed under control longer. Also, because Abraxane does not contain Cremophor like Taxol, you do not have to take steroids before you receive Abraxane.
Keep in mind that the side effects of Abraxane are similar to those of Taxol:
- neutropenia (low white blood cell counts),
- neuropathy (pain and numbness),
- weakness, and
- infection.
In the Phase III trial, fewer women had neutropenia with Abraxane than with Taxol. But MORE women had neuropathy with Abraxane than with Taxol. However, the pain and numbness seemed to resolve more quickly in the women who took Abraxane.
So far, we don't know if Abraxane improves overall survival rates. More research is needed in this important area.
In this study, Abraxane was given every three weeks. Soon studies will be done to look at other intervals: every one to two weeks, for example.
Abraxane has not yet been tested against Taxotere. In women with metastatic disease, Taxotere was found to be more effective than Taxol. Taxotere also does not require Cremophor. So it will be interesting to see whether Abraxane and Taxotere have similar or equal benefits.
If you have metastatic cancer that is not responding to other chemotherapy, talk to your doctor about all your options, including Abraxane. If you are receiving Taxol now and are having problems with side effects from it or from pre-treatment steroids, you also may want to talk to your doctor about Taxotere or Abraxane.
If you sense that information on this new medication is new to your doctor, you can refer him or her to breastcancer.org. You can also have your doctor call 1-800-564-0216 to learn more about Abraxane treatment.
Researchers are constantly searching for new and better treatments. And remember that whenever there are new advances in treating recurrent disease, breastcancer.org will bring you the details—so you can make the best decisions for YOU.
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