Paclitaxel Versus Docetaxel for Early Breast Cancer
In a study comparing different dosing schedules of two common breast cancer drugs, weekly treatment with the drug paclitaxel (Taxol) in addition to standard chemotherapy proved most effective in extending overall survival and disease-free survival among women with early-stage breast cancer. Treatment with the drug docetaxel (Taxotere) every three weeks improved patients’ disease-free survival and is also an acceptable choice.
New England Journal of Medicine, April 17, 2008 (see the journal abstract)
(N Engl J Med. 2008 Apr 17;358(16):1663-71)
Women with early-stage breast cancer have a lower risk of cancer recurrence and a better chance of survival when they are treated with chemotherapy in addition to surgery (adjuvant chemotherapy). Previous studies have shown that the risk of a recurrence is further reduced when patients receive a drug from a class known as taxanes (docetaxel or paclitaxel) in addition to the standard drugs doxorubicin and cyclophosphamide.
Questions have persisted, however, about whether one taxane is superior to the other and whether outcomes for patients treated with paclitaxel are better when the drug is given once a week instead of on a conventional once-every-three-weeks schedule.
This phase III study involved 4,950 women with breast cancer that was considered at high risk of recurrence, either because the tumor was at least two centimeters in size or because the cancer had already spread to lymph nodes in the armpit. All of the women had had either a mastectomy or lumpectomy and some had also had radiation therapy. Those whose tumors were sensitive to the hormones estrogen or progesterone also took an antihormonal drug (tamoxifen or an aromatase inhibitor) for five years.
After completing chemotherapy with doxorubicin and cyclophosphamide, the women were randomly assigned to one of four groups.
- One group received paclitaxel every three weeks (standard treatment)
- A second group received docetaxel every three weeks
- A third group received paclitaxel once a week
- A fourth group received docetaxel once a week
The study was coordinated by the Eastern Cooperative Oncology Group, a National Cancer Institute (NCI) sponsored clinical trials cooperative group (see the protocol summary). Three other NCI-sponsored cooperative groups (the Southwest Oncology Group, the Cancer and Leukemia Group B, and the North Central Cancer Treatment Group) also participated. The principal investigator was Joseph A. Sparano, M.D., of Montefiore Medical Center in New York City.
The patients were followed for a median follow-up period of just over five years. When the researchers compared outcomes for women treated with paclitaxel vs. docetaxel and those treated weekly vs. every three weeks, they found no significant differences. However, when they broke out the four treatment groups and compared them, they did find differences.
Compared with women who received standard, once-every-three-weeks paclitaxel, those who received docetaxel every three weeks had better disease-free survival (that is, cancer recurrence was delayed for longer) as did those who received weekly paclitaxel. However, women in the weekly paclitaxel group also lived longer overall.
Rates of treatment side effects differed in the four treatment groups. Women who received docetaxel every three weeks had the highest rates of low white blood cell counts, which can cause complications such as infection and fever. Women treated with weekly paclitaxel had more pain, numbness, tingling, swelling, or muscle weakness in the arms and legs than patients in any other treatment group.
“This study addresses several very practical, important questions about taxane choice, dose, and treatment schedule for patients with early breast cancer,” comments Jo Anne Zujewski, M.D., head of Breast Cancer Therapeutics in NCI’s Division of Cancer Treatment and Diagnosis.
“Weekly paclitaxel showed a survival advantage, but docetaxel given every three weeks could also be an acceptable choice - for example, if weekly treatment is impractical because of the need to travel or take time off from work, or if an individual patient tolerates docetaxel better. One of the interesting things about this study is that it shows that not all taxanes are alike.”