Efficacy of weekly paclitaxel in patients with docetaxel-resistant metastatic breast cancer

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Abstract
Background. Partial cross-resistance to paclitaxel and docetaxel has been demonstrated in pre-clinical studies. Patients and methods. We retrospectively evaluated the efficacy of weekly paclitaxel 80 mg/m2 in 82 patients with docetaxel-resisitant metastatic breast cancer. Docetaxel resistance was classified into primary resistance, defined as progressive disease while receiving docetaxel, and secondary resistance, defined as progression after achievement of a documented clinical response to docetaxel. Secondary resistance was subclassified according to the interval between the final infusion of docetaxel and the start of weekly paclitaxel into: (1) short interval, ≦120 days, and (2) long interval, >120 days. Results. The response rate of the 82 patients was 19.5% (95% confidence interval, 10.8–27.9%). The response rate according to the docetaxel resistance category was: primary resistance (n=24), 8.3%; secondary resistance (n=58), 24.1% (short interval [n=39], 17.9%, and long interval, [n=19], 36.8%). The differences in response rates among the three categories were statistically significant (p=0.0247, Cochran–Mantel–Haenszel test). The interval between from the final docetaxel infusion and disease progression were predictors for response of weekly paclitaxel. Conclusion. Weekly paclitaxel is modestly effective and safe in docetaxel-resistant metastatic breast cancer patients. However, weekly paclitaxel should not be recommended for primary resistance patients with docetaxel.