Paclitaxel activity in anthracycline refractory breast cancer patients

We investigated the efficacy and tolerability of two doses of paclitaxel, 175 mg/m2 and 135 mg/m2, over a 3-hr infusion, without prophylactic G-CSF, in heavily pretreated patients with anthracycline-resistant breast cancer. Although paclitaxel may share with anthracyclines a common mechanism of drug resistance, there is evidence that the two drugs are not completely cross resistant.

From July 1994 to January 1996, 42 patients were treated every 3 weeks, for a maximum of 6 cycles; paclitaxel dose was established according to pretreatment extension.

In 41 assessable patients we observed 9 partial responses, for an overall response rate of 22% (95% CI, 10-34%). There was no difference in response rate between the two dose levels. Median duration of response was 9 months, median time to progression 5 months, and median survival 9 months. The dose-limiting toxicity was neutropenia, which was grade 3-4 in 40% (135 mg/m2) and 62% (175 mg/m2) of the patients (P = 0.28); neutropenic fever occurred in 24% of the patients, without significant differences between the two dose levels. Other toxicity was mild to moderate.

Paclitaxel at doses of 175 mg/m2 or 135 mg/m2 is active and well tolerated in advanced breast cancer patients resistant to anthracyclines. The prophylactic use of colony-stimulating factors seems appropriate in heavily pretreated patients given the higher dose level.