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    Posted: 09/12/2005
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Weekly Paclitaxel (Taxol®) Before Any Other Treatment Improves Outcomes in Early-Stage Breast Cancer

Key Words

Breast cancer, paclitaxel (Taxol®). (Definitions of many terms related to cancer can be found in the Cancer.gov Dictionary.)

Summary

Women with invasive, early-stage breast cancer who were given the drug paclitaxel (Taxol®) weekly prior to receiving other therapy had a higher response rate compared with conventional administration of the drug every three weeks.

Source

Journal of Clinical Oncology, published online August 8, 2005; in print September 1, 2005 (see the journal abstract).

Background

Conventional cancer chemotherapy is usually given at three-week intervals. In recent years, however, some researchers have begun to investigate “dose-dense” drug regimens where chemotherapy drugs are given more frequently, such as once a week or once every two weeks. The drug dose is either kept the same or is lowered slightly. The idea is that exposing cancer cells to the drugs more frequently may kill more cells and thus improve the effectiveness of chemotherapy.

Recent studies have shown that among patients with metastasized breast cancer (cancer that has spread to other parts of the body), weekly treatment with the drug paclitaxel (Taxol®) resulted in a higher response rate and a longer delay until patients’ disease progressed, compared with conventional administration of the drug every three weeks (see related story). Other studies have suggested that weekly administration of paclitaxel might improve outcomes for a different group of women: those with invasive, early-stage breast cancer.

When patients are newly diagnosed with invasive breast cancer, the standard therapy usually begins with surgery followed by chemotherapy. However, a growing number of such patients are undergoing what is called neoadjuvant chemotherapy or primary systemic chemotherapy. This is where drug therapy is given in the weeks before the surgery – to help shrink tumor size and reduce the amount of tissue that needs to be removed.

The primary goal of the study described here was to further explore whether weekly paclitaxel prior to surgery or other treatment would benefit women with invasive, early-stage breast cancer.

The Study

A total of 480 women with invasive, early-stage breast cancer enrolled in this phase III trial between November 1998 and July 2001. Of those, 258 women who had not yet undergone surgery were randomly assigned to receive paclitaxel either weekly (131 patients) or on the conventional once-every-three-weeks schedule (127 patients). In the weekly paclitaxel group, 56 patients had cancer in their lymph nodes (node-positive); 75 appeared to be node-negative. In the conventionally treated control group, 54 were node-positive and 73 were node-negative.

The group receiving weekly paclitaxel was further divided into a high-dose group and a low-dose group. Those whose cancer had already spread to the lymph nodes received the higher dose; those who were node-negative received the lower dose. Patients in the high-dose group were subsequently administered a smaller dose mid-trial as a result of severe side effects, though this adjusted high dose was still almost twice as much as the low dose.

Upon completion of the paclitaxel, all patients were given a standard treatment of fluorouracil plus doxorubicin plus cyclophosphamide (FAC) chemotherapy every three weeks for four cycles.

The remaining 222 patients enrolled in the study received therapy in the adjuvant setting; that is, they received the paclitaxel after another primary treatment, such as surgery. Findings from these patients will be provided in another article.

This study’s lead author is Marjorie C. Green, M.D., University of Texas M.D. Anderson Cancer Center, Houston, Texas.

Results

The weekly schedule of paclitaxel significantly improved the chances that all signs of invasive breast cancer in the breast and lymph nodes would be eradicated. After completion of paclitaxel and FAC, 15.7 percent of patients in the once-every-three-weeks paclitaxel group were free of invasive cancer cells as compared to 28.2 percent of patients in the weekly paclitaxel group.

This result was statistically significant and was true regardless of whether the patient was node-positive or node-negative. There was no significant difference in response between the higher-dose versus the lower-dose weekly paclitaxel subgroups.

Among patients treated with weekly paclitaxel, there were more nervous system side effects but fewer instances of low blood counts.

Comments

“We have shown that changing the schedule of paclitaxel results in significantly improved ability to eradicate invasive cancer in both the breast and lymph nodes,” conclude Green and the other study authors. In an accompanying editorial, Andrew D. Seidman, M.D., of Memorial Sloan-Kettering Cancer Center in New York wrote: “…taken together [this and other studies] all suggest a promising future for decreasing paclitaxel dose intervals in the management of earlier-stage disease.”

According to Jennifer Eng-Wong, M.D., M.P.H., a medical oncologist with the National Cancer Institute’s Center for Cancer Research, “This study supports a number of [other] studies that examine the dose interval for paclitaxel. It provides mounting evidence that the timing of chemotherapy is important. The shorter dose interval is going to be better for metastatic and adjuvant therapy for breast cancer.”

Limitations

While the study shows promise for weekly paclitaxel in the management of early-stage breast cancer, said Eng-Wong, it does not provide any information about the impact of the shorter drug schedule on overall survival rates.

Also, note the study’s authors, the ideal dose of weekly paclitaxel has not yet been defined, though the toxicity of the higher dose used here limits its usefulness. “Whether increasing, or even decreasing, the [low] dose of paclitaxel will result in a superior outcome is to be determined,” they wrote.

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