Taxane resistance in breast cancer: mechanisms, predictive biomarkers and circumvention strategies

BACKGROUND

Taxanes are established in the treatment of metastatic breast cancer (MBC) and early breast cancer (EBC) as potent chemotherapy agents. However, their therapeutic usefulness is limited by de-novo refractoriness or acquired resistance, which are common drawbacks to most anti-cancer cytotoxics. Considering that the taxanes will remain principle chemotherapeutic agents for the treatment of breast cancer, we reviewed known mechanisms of resistance in with an outlook of optimizing their clinical use.

METHODS

We searched the PubMed and MEDLINE databases for articles (from inception through to 9th January 2012; last search 10/01/2012) and journals known to publish information relevant to taxane chemotherapy. We imposed no language restrictions. Search terms included: cancer, breast cancer, response, resistance, taxane, paclitaxel, docetaxel, taxol. Due to the possibility of alternative mechanisms of resistance all combination chemotherapy treated data sets were removed from our overview.

RESULTS

Over-expression of the MDR-1 gene product Pgp was extensively studied in vitro in association with taxane resistance, but data are conflicting. Similarly, the target components microtubules, which are thought to mediate refractoriness through alterations of the expression pattern of tubulins or microtubule associated proteins and the expression of alternative tubulin isoforms, failed to confirm such associations. Little consensus has been generated for reported associations between taxane-sensitivity and mutated p53, or taxane-resistance and overexpression of Bcl-2, Bcl-xL or NFkB. In contrary sufficient in vitro data support an association of spindle assembly checkpoint (SAC) defects with resistance. Clinical data have been limited and inconsistent, which relate to the variety of methods used, lack of standardization of cut-offs for quantitation, differences in clinical endpoints measured and in methods of tissue collection preparation and storage, and study/patient heterogeneity. The most prominent finding is that pharmaceutical down-regulation of HER-2 appears to reverse the taxane resistance.

CONCLUSIONS

Currently no valid practical biomarkers exist that can predict resistance to the taxanes in breast cancer supporting the principle of individualized cancer therapy. The incorporation of several biomarker analyses into prospectively designed studies in this setting are needed.

Adjuvant trastuzumab in HER2-positive breast cancer

BACKGROUND

Trastuzumab improves survival in the adjuvant treatment of HER-positive breast cancer, although combined therapy with anthracycline-based regimens has been associated with cardiac toxicity. We wanted to evaluate the efficacy and safety of a new nonanthracycline regimen with trastuzumab.

METHODS

We randomly assigned 3222 women with HER2-positive early-stage breast cancer to receive doxorubicin and cyclophosphamide followed by docetaxel every 3 weeks (AC-T), the same regimen plus 52 weeks of trastuzumab (AC-T plus trastuzumab), or docetaxel and carboplatin plus 52 weeks of trastuzumab (TCH). The primary study end point was disease-free survival. Secondary end points were overall survival and safety.

RESULTS

At a median follow-up of 65 months, 656 events triggered this protocol-specified analysis. The estimated disease-free survival rates at 5 years were 75% among patients receiving AC-T, 84% among those receiving AC-T plus trastuzumab, and 81% among those receiving TCH. Estimated rates of overall survival were 87%, 92%, and 91%, respectively. No significant differences in efficacy (disease-free or overall survival) were found between the two trastuzumab regimens, whereas both were superior to AC-T. The rates of congestive heart failure and cardiac dysfunction were significantly higher in the group receiving AC-T plus trastuzumab than in the TCH group (P<0.001). Eight cases of acute leukemia were reported: seven in the groups receiving the anthracycline-based regimens and one in the TCH group subsequent to receiving an anthracycline outside the study.

CONCLUSIONS

The addition of 1 year of adjuvant trastuzumab significantly improved disease-free and overall survival among women with HER2-positive breast cancer. The risk-benefit ratio favored the nonanthracycline TCH regimen over AC-T plus trastuzumab, given its similar efficacy, fewer acute toxic effects, and lower risks of cardiotoxicity and leukemia. (Funded by Sanofi-Aventis and Genentech; BCIRG-006 ClinicalTrials.gov number, NCT00021255.).

Added value of molecular targeted agents in oncology

The treatment of certain cancers has been revolutionised in recent years by the introduction of novel drugs designed to target specific molecular factors implicated in tumour growth. Notable examples include trastuzumab, a humanized monoclonal antibody (mAb) against human epidermal growth factor receptor (HER)-2 in women with HER2-positive breast cancer; rituximab, an anti-CD20 mAb in patients with non-Hodgkin's lymphoma; imatinib, a tyrosine kinase inhibitor in KIT-positive gastrointestinal stromal tumours and sunitinib, another tyrosine kinase inhibitor, in metastatic renal cell carcinoma. For regulatory reasons, new molecular targeted agents are first evaluated in advanced and metastatic disease, wherein they prolong survival. However, their most profound impact has been observed in the adjuvant setting, where they may contribute to curative therapy rather than mere palliation. Expansion in the use of molecular targeted therapies will have important cost implications for health care systems. Although expensive, on a monthly basis, molecular targeted therapies may not be more costly than treatments for other major chronic diseases, especially considering the contribution of cancer to the global disease burden, the associated socioeconomic costs and the long-term benefits of therapy. Nevertheless, the use of these agents must be optimised, in part using molecular biomarkers associated with drug response.

Phase III Randomized Study Comparing Docetaxel Plus Trastuzumab With Vinorelbine Plus Trastuzumab As First-Line Therapy of Metastatic or Locally Advanced Human Epidermal Growth Factor Receptor 2–Positive Breast Cancer: The HERNATA Study

Purpose

To evaluate docetaxel or vinorelbine, both with trastuzumab, as first-line therapy of human epidermal growth factor receptor 2–positive advanced breast cancer.

Patients and Methods

Patients naive to chemotherapy for advanced disease were randomly assigned to docetaxel 100 mg/m2day 1 or vinorelbine 30 to 35 mg/m2on days 1 and 8, both combined with trastuzumab (8-mg/kg loading dose and 6-mg/kg maintenance dose) on day 1 every 3 weeks. The primary end point was time to progression (TTP).

Results

A total of 143 patients were randomly allocated to docetaxel, and 141 patients were assigned to vinorelbine. The median TTP for docetaxel and vinorelbine respectively was 12.4 months versus 15.3 months (hazard ratio [HR] = 0.94; 95% CI, 0.71 to 1.25; P = .67), median overall survival was 35.7 months versus 38.8 months (HR = 1.01; 95% CI, 0.71 to 1.42; P = .98), and the 1-year survival rate was 88% in both arms. Median time to treatment failure for study chemotherapy was 5.6 months versus 7.7 months (HR = 0.50; 95% CI, 0.38 to 0.64; P < .0001). The investigator-assessed overall response rate among 241 patients with measurable disease were 59.3% in both arms. More patients in the docetaxel arm discontinued therapy due to toxicity (P < .001). Significantly more treatment-related grade 3 to 4 febrile neutropenia (36.0% v 10.1%), leucopenia (40.3% v 21.0%), infection 25.1% v 13.0%), fever (4.3% v 0%), neuropathy (30.9% v 3.6%), nail changes (7.9% v 0.7%), and edema (6.5% v 0%) were reported with docetaxel.

Conclusion

The study failed to demonstrate superiority of any drug in terms of efficacy, but the vinorelbine combination had significantly fewer adverse effects and should be considered as an alternative first-line option.

Rational use of trastuzumab in metastatic and locally advanced breast cancer: implications of recent research

The management of HER2-positive metastatic breast cancer, a disease renowned for its aggressive natural history, has been revolutionized by the introduction of trastuzumab. Indeed, outcomes for patients with HER2-positive advanced breast cancer are now equivalent to, if not better than, those of their HER2-negative counterparts. Since the pivotal registration trial, a wealth of new clinical data has emerged regarding the use of trastuzumab in a variety of clinical contexts - adding to the evidence but also highlighting areas of uncertainly and debate. These include the optimal partner chemotherapy(ies) to trastuzumab; the effectiveness of combining trastuzumab with endocrine therapy; the benefits of continuing trastuzumab after progression on a trastuzumab-containing regimen; and the role of trastuzumab in locally advanced and inflammatory breast cancer. In this paper we review major clinical trials addressing these questions, clinical recommendations that can be made as a result, and the strength of evidence that supports them. Finally, we identify areas of ongoing uncertainty, and propose recommendations for future research in this field.

Looking beyond surveillance, epidemiology, and end results: patterns of chemotherapy administration for advanced non-small cell lung cancer in a contemporary, diverse population

INTRODUCTION

Chemotherapy prolongs survival without substantially impairing quality of life for medically fit patients with advanced non-small cell lung cancer (NSCLC), but population-based studies have shown that only 20 to 30% of these patients receive chemotherapy. These earlier studies have relied on Medicare-linked Surveillance, Epidemiology, and End Results (SEER) data, thus excluding the 30 to 35% of lung cancer patients younger than 65 years. Therefore, we determined the use of chemotherapy in a contemporary, diverse NSCLC population encompassing all patient ages.

METHODS

We performed a retrospective analysis of patients diagnosed with stage IV NSCLC from 2000 to 2007 at the University of Texas Southwestern Medical Center. Demographic, treatment, and outcome data were obtained from hospital tumor registries. The association between these variables was assessed using univariate analysis and multivariate logistic regression.

RESULTS

In all, 718 patients met criteria for analysis. Mean age was 60 years, 58% were men, and 45% were white. Three hundred fifty-three patients (49%) received chemotherapy. In univariate analysis, receipt of chemotherapy was associated with age (53% of patients younger than 65 years versus 41% of patients aged 65 years and older; p = 0.003) and insurance type (p < 0.001). In a multivariate model, age and insurance type remained associated with receipt of chemotherapy. For individuals receiving chemotherapy, median survival was 9.2 months, compared with 2.3 months for untreated patients (p < 0.001).

CONCLUSIONS

In a contemporary population representing the full age range of patients with advanced NSCLC, chemotherapy was administered to approximately half of all patients-more than twice the rate reported in some earlier studies. Patient age and insurance type are associated with receipt of chemotherapy.

A phase II trial of trastuzumab plus weekly ixabepilone and carboplatin in patients with HER2-positive metastatic breast cancer: an Eastern Cooperative Oncology Group Trial

The epothilone B analogue, ixabepilone, binds to b-tubulin, is effective for taxane-refractory metastatic breast cancer (MBC), and may be given every 3 weeks or weekly. We evaluated the efficacy of weekly ixabepilone (I) plus trastuzumab (T) and carboplatin (C) as first line therapy in HER2 + MBC. Patients with HER2+ (3+ by IHC or FISH amplified) MBC received I (15 mg/m2 IV) and C (area under the curve, AUC = 2 IV) on days 1, 8, and 15 of a 28-day cycle for a maximum of 6 cycles, plus weekly T (4 mg/kg loading dose then 2 mg/kg IV) during chemotherapy then every 3 weeks (6 mg/kg IV) until disease progression. The primary objective was to determine whether the combination was associated with a response rate (RR) of at least 75%. Fifty-nine patients were treated, and 39 had HER2 overexpression confirmed in a central lab (cHER2+). For all treated patients, objective response occurred in 26 patients (44%; 95% CI 31-58%), median time to progression was 8.2 months (95% CI 6.3-9.9), and median overall survival was 34.7 months (95% CI 25.7 to [not reached]). Results were comparable for cHer2? cancers. Grade 3-4 adverse events included neutropenia (49%), thrombocytopenia (14%), fatigue (12%), nausea (7%), diarrhea (7%), and neuropathy (7%). One patient died from treatment complications during cycle 1. Weekly ixabepilone and carboplatin plus trastuzumab have an acceptable toxicity profile, but are not likely to be associated with an RR of 75% in HER2+ MBC. Efficacy appears comparable to paclitaxel, carboplatin, and trastuzumab.

Novel combinations for the treatment of metastatic breast cancer

Anthracyclines and taxanes represent the mainstay of first-line cytotoxic therapy for metastatic breast cancer (MBC), but most patients eventually develop resistance to these agents. Consequently, alternative combinations for MBC therapy are the subject of much ongoing research. Capecitabine and ixabepilone is the only chemotherapy combination specifically approved for MBC after failure of anthracyclines and taxanes. Other options have limited data to support their use in this setting but are commonly used in practice. Future MBC therapies will likely combine alternative chemotherapies and novel biologic agents, and numerous ongoing trials should help to further define the proper use of these regimens.

Trastuzumab as the lead monoclonal antibody in advanced breast cancer: choosing which patient and when

Trastuzumab is the first of the monoclonal antibodies to be used in the treatment of those patients who have HER2-positive metastatic breast cancer. It is most effective when combined with cytotoxics, such as the taxanes and vinorelbine. It is well-tolerated but associated cardiotoxicity makes use with anthracyclines and in patients with cardiac dysfunction problematic. A further adverse observation is that the rate of development of cerebral metastases is 2.8-times higher in patients who have received trastuzumab as part of their treatment regimens. Trastuzumab has been combined with cytotoxics, hormones, other monoclonal antibodies, such a pertuzumab and bevacizumab, and targeted small molecules such as lapatinib, and it can be conjugated with cytotoxics to deliver them to cancer cells. The dosage, duration of therapy and optimal combinations in advanced and early stage breast cancer and use after relapse are still being defined.