Explanation on resistance to taxane class of drugs [Archive]

gdpawel

12-15-2007, 08:21 PM

CNS relapses are common among breast cancer patients treated with a taxane-based chemotherapy regimen

Central Nervous System Relapse in Patients With Breast Cancer Is Associated With Advanced Stages, With CK-19 mRNA-positive Circulating Occult Tumor Cells and With HER2/neu-positive tumor

John Souglakos; Lambros Vamvakas; Stella Apostolaki; Maria Perraki; Zacharenia Saridaki; Irine Kazakou; Athanasios Pallis; Charalambos Kouroussis; Nikos Androulakis; Kostas Kalbakis; Georgia Millaki; Dimitris Mavroudis; Vassilis Georgoulias

Abstract

Introduction: To evaluate the incidence of central nervous system (CNS) involvement in patients with breast cancer treated with a taxane-based chemotherapy regimen and to determine predictive factors for CNS relapse.

Methods: The medical files of patients with early breast cancer (n = 253) or advanced stage breast cancer (n = 239) as well of those with other solid tumors (n = 336) treated with or without a taxane-based chemotherapy regimen during a 42-month period were reviewed. HER2/neu overexpression was identified by immunohistochemistry, whereas cytokeratin 19 (CK-19) mRNA-positive circulating tumor cells (CTCs) in the peripheral blood were identified by real-time PCR.

Results: The incidence of CNS relapse was similar in patients suffering from breast cancer or other solid tumors (10.4% and 11.4%, respectively; P = 0.517). The incidence of CNS relapse was significantly higher in breast cancer patients with advanced disease (P = 0.041), visceral disease and bone disease (P = 0.036), in those who were treated with a taxane-containing regimen (P = 0.024), in those with HER2/neu-overexpressing tumors (P = 0.022) and, finally, in those with detectable CK-19 mRNA-positive CTCs (P = 0.008). Multivariate analysis revealed that the stage of disease (odds ratio, 0.23; 95% confidence interval, 0.007-0.23; P = 0.0001), the HER2/neu status (odds ratio, 29.4; 95% confidence interval, 7.51-101.21; P = 0.0001) and the presence of CK-19 mRNA-positive CTCs (odds ratio, 8.31; 95% confidence interval, 3.97-12.84; P = 0.001) were independent predictive factors for CNS relapse.

Conclusion: CNS relapses are common among breast cancer patients treated with a taxane-based chemotherapy regimen, patients with HER2/neu-positive tumor and patients with CK-19 mRNA-positive CTCs.

Breast Cancer Res. 2006;8(4) ©2006 BioMed Central, Ltd.

During the past years it has been frequently observed that patients with breast cancer treated with a taxane-containing chemotherapy regimen, either in the adjuvant setting or in the metastatic setting, presenting central nervous system (CNS) involvement as the only evidence of disease progression. We were therefore interested to evaluate the incidence of CNS metastases in patients with early and advanced breast cancer treated with a taxane-containing chemotherapy regimen and to identify predictive factors for CNS relapse.

Recent studies reported that breast cancer patients who received a taxane-containing chemotherapy regimen had a significantly higher incidence of CNS metastases compared with that of patients treated with a nontaxane-containing regimen. There are also data indicating an increased risk for brain metastases in breast cancer patients receiving trastuzumab (Herceptin).

In the present study it was also possible to confirm the initial clinical observation that breast cancer patients who receive a taxane-containing chemotherapy regimen have a significantly higher incidence of CNS metastases compared with that of patients treated with a nontaxane-containing regimen.

The reasons for the association between treatment of breast cancer with a taxane-containing chemotherapy regimen and an increased incidence of CNS involvement could be that taxanes are very lipophilic, their concentration in the CNS is very low after their intravenous administration. Taxanes are unable to penetrate the intact blood-brain barrier, the concentration of radiolabeled paclitaxel in the cerebrospinal fluid is found to be significantly lower than in other organs, and thus undetectable in the brain, in the spinal cord or in any other site of the CNS.

Also, paclitaxel is exported from the p-glycoprotein and other ATP-binding cassette transporters placed at the luminal membrane of brain capillaries, as an explanation for the low concentrations of taxanes in the CNS.

Furthermore, the detection of cytokeratin 19 (CK-19) and of mRNA-positive circulating tumor cells (CTCs) in the peripheral blood and the bone marrow of patients with breast cancer is correlated with increased incidence of relapse.

The aforementioned data suggest that taxanes may not penetrate well into the CNS, and therefore the CNS may represent tumor 'sanctuary' sites for taxane-containing chemotherapy regimens. A difference in the incidence of CNS relapses between patients with breast cancer and other solid tumors treated with taxanes was observed.