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According to the results of a study conducted in Japan, an investigational drug known as dofequidar fumarate (MS-209) may prevent or reverse multidrug resistance in subsets of patients receiving chemotherapy for advanced or recurrent breast cancer. These results were published in the Journal of Clinical Oncology.

Patients diagnosed with Stage IV or metastatic breast cancers have disease that has spread from the affected breast to one or more distant sites in the body. Historically, metastatic breast cancer has been considered incurable; the goal of treatment has been to provide relief from symptoms and prolong the duration and quality of life. However, there have been some important advances resulting in the addition of many more treatment options for managing this disease. These include the now widespread use of taxane chemotherapy, the development of targeted therapies, and the development of more active hormonal therapy drugs.

Recurrent breast cancer is cancer that progresses during treatment or recurs after a remission. Although breast cancer may recur almost anywhere in the body, common locations include the liver, bones, lungs, brain, and skin. Treatment for recurrent breast cancer depends on which treatments the patient has already received and where the cancer has recurred.

While chemotherapy provides effective treatment for many breast cancer patients, some patients are resistant to chemotherapy initially or develop resistance over time. Researchers are therefore evaluating investigational drugs-such as dofequidar fumarate (MS-209)-that are intended to prevent or overcome chemotherapy resistance. If safe and effective, these drugs could be combined with chemotherapy in order to increase chemotherapy effectiveness.

To evaluate the safety and effectiveness of dofequidar, researchers in Japan conducted a Phase III clinical trial among 221 women with Stage IV or recurrent breast cancer. All women received chemotherapy consisting of cyclophosphamide, doxorubicin, and fluorouracil. Half the women also received dofequidar.

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  • Overall, there was a suggestion that women treated with chemotherapy plus dofequidar were more likely to experience a complete or partial reduction of detectable cancer than women treated with chemotherapy alone. This result did not meet the criteria for statistical significance, however, suggesting that it may have occurred by chance alone.
  • A benefit of dofequidar was observed in certain subsets of patients. The addition of dofequidar improved progression-free survival in women who were premenopausal, had received no prior therapy, and were Stage IV at diagnosis.
  • Women treated with dofequidar and chemotherapy were more likely than women treated with chemotherapy alone to experience reductions in white blood cell levels.

While this study did not find an overall benefit of dofequidar fumarate in women undergoing chemotherapy for advanced or recurrent breast cancer, it’s possible that specific subsets of patients may benefit. Additional studies will be necessary to address this question.

Reference: Saeki T, Momizu T, Toi M et al. Dofequidar fumarate (MS-209) in combination with cyclophosphamide, doxorubicin, and fluorouracil for patients with advanced or recurrent breast cancer. Journal of Clinical Oncology. 2007;25:411-417.

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