Results from a clinical trial comparing the effectiveness of the drugs paclitaxel and docetaxel, delivered over two different dosing schedules, showed that both drugs regardless of the dosing schedules tested in this trial provided similar benefits for women with stage II or III, operable breast cancer. However, more women treated with docetaxel than with paclitaxel experienced serious side effects from their treatment.
The trial was led by the Eastern Cooperative Oncology Group in collaboration with the Cancer and Leukaemia Group B, North Central Cancer Treatment Group (NCCTG), and the Southwest Oncology Group. The National Cancer Institute (NCI), part of the National Institutes of Health, supported this phase III randomised clinical trial, states a NIH release.
Paclitaxel and docetaxel are members of a class of drugs called taxanes, and both are approved for the treatment of patients with breast cancer that has spread to the lymph nodes. Although these drugs have been shown to be beneficial in treating breast cancer, this is the first time they have been directly compared and the first time that a weekly dosing schedule has been compared with a standard every three-week dosing schedule in the treatment of early-stage breast cancer.
“Although both drugs are used as adjuvant breast cancer treatments, which is most effective has been a question for many years. Now doctors and patients will be able to consider side effects, convenience, and cost in determining taxane treatment without concern that effectiveness will be compromised,” said JoAnne Zujewski, who oversees breast cancer trials for NCI's Cancer Therapy Evaluation Programme.
A total of 4,988 women were enrolled in the trial between 1999 and 2002. All of the women had axillary lymph node (a lymph node in the armpit region that drains lymph channels from the breast) positive or high-risk (their tumour was at least 2 centimetres in size) node-negative breast cancer. All of the women were first treated with doxorubicin and cyclophosphamide, a standard treatment protocol referred to as AC (representing the drugs doxorubicin and cyclophosphamide). Following AC chemotherapy, patients were randomly assigned to groups that received either paclitaxel or docetaxel, administered weekly for 12 weeks or every third week over a 12-week period.
The women were followed for a median time of about four years. Over the course of this period, the investigators observed 856 disease-free survival events across all regimens. Disease-free survival is the time during which no cancer is found. In contrast, disease-free survival events have a different meaning. They are defined as a recurrence of breast cancer, a new second primary breast cancer in the opposite breast, or death without evidence of recurrent breast cancer. The vast majority of women (83 per cent) remain event-free at this time.
This trial also compared the efficacy of different taxane treatment schedules, using paclitaxel given every three weeks as the current standard of care. In this secondary analysis, there was a trend toward fewer disease-survival events among women who received weekly paclitaxel treatments compared with paclitaxel given every three weeks, added the release.
"Previous studies in patients where cancer had spread to other parts of the body have shown that docetaxel is more effective than paclitaxel when given every 3 weeks, and that paclitaxel is more effective if given weekly rather than every 3 weeks. This study addressed a question that many medical oncologists have had for some time about whether this would translate into improved success rates for patients with stage II and III disease. At this time, this does not appear to be the case, but further follow-up will be required to confirm our initial findings,” said Joseph Sparano, director of the Breast Evaluation Centre at the Montefiore-Einstein Cancer Centre, and clinical trial leader.