Weekly Paclitaxel in Pretreated Metastatic Breast Cancer: Retrospective Analysis of 52 Patients

Generalized principles of stochasticity can be used to control dynamic heterogeneity

It is increasingly appreciated that phenotypic stochasticity plays fundamental roles in biological systems at the cellular level and that a variety of mechanisms generates phenotypic interconversion over a broad range of time scales. The ensuing dynamic heterogeneity can be used to understand biological and clinical processes involving diverse phenotypes in different cell populations. The same principles can be applied, not only to populations composed of cells, but also to populations composed of molecules, tissues, and multicellular organisms. Stochastic units generating dynamic heterogeneity can be integrated across various length scales. We propose that a graphical tool we have developed, called a metronomogram, will allow us to identify factors that suitably influence the restoration of homeostatic heterogeneity so as to modulate the consequences of dynamic heterogeneity for desired outcomes.

Conceptualizing a tool to optimize therapy based on dynamic heterogeneity

Complex biological systems often display a randomness paralleled in processes studied in fundamental physics. This simple stochasticity emerges owing to the complexity of the system and underlies a fundamental aspect of biology called phenotypic stochasticity. Ongoing stochastic fluctuations in phenotype at the single-unit level can contribute to two emergent population phenotypes. Phenotypic stochasticity not only generates heterogeneity within a cell population, but also allows reversible transitions back and forth between multiple states. This phenotypic interconversion tends to restore a population to a previous composition after that population has been depleted of specific members. We call this tendency homeostatic heterogeneity. These concepts of dynamic heterogeneity can be applied to populations composed of molecules, cells, individuals, etc. Here we discuss the concept that phenotypic stochasticity both underlies the generation of heterogeneity within a cell population and can be used to control population composition, contributing, in particular, to both the ongoing emergence of drug resistance and an opportunity for depleting drug-resistant cells. Using notions of both 'large' and 'small' numbers of biomolecular components, we rationalize our use of Markov processes to model the generation and eradication of drug-resistant cells. Using these insights, we have developed a graphical tool, called a metronomogram, that we propose will allow us to optimize dosing frequencies and total course durations for clinical benefit.

A literature-based meta-analysis taxane-based doublet versus single-agent taxane chemotherapy in patients with advanced breast cancer

PURPOSE

Clinical trials have reported conflicting results as to whether taxane-based doublet improves outcome over single-agent taxane in patients with advanced breast cancer.

METHODS

We performed a meta-analysis comparing primary and secondary end points of taxane-based doublet with single-agent taxane chemotherapy in patients with advanced breast cancer and prior anthracycline treatment. The event-based relative risk ratio (RR) with 95% confidence intervals (95% CI) was derived, and a test of heterogeneity was applied.

RESULTS

Four eligible trials (2,343 patients) were selected from 488 studies that initially were identified. A significant difference in favoring taxane-based doublet over single-agent taxane was observed in progression-free survival (PFS) (RR, 1.33; 95% CI, 1.02-1.75; P = 0.039) and partial response (PR) (RR, 1.43; 95% CI, 1.10-1.86; P = 0.008). The ORR was higher for patients receiving taxane-based doublet, although not statistically significant (RR, 1.17; 95% CI, 0.91-1.50; P = 0.220). Whereas there was no difference in 1-year survival rate (1-year SR) (RR, 1.05; 95% CI, 0.94-1.17; P = 0.422), clinical benefit (CB) (RR, 1.02; 95% CI, 0.95-1.09; P = 0.642), and complete response (CR) (RR, 0.75; 95% CI, 0.31-1.79; P = 0.512). Toxicities did not differ significantly except stomatitis and diarrhea.

CONCLUSION

Taxane-based doublet appeared to improve PFS and PR compared with single-agent taxane in the treatment of patients with advanced breast cancer. Further prospective, randomized, controlled trials will be necessary.

Weekly administration of docetaxel and paclitaxel in metastatic or advanced breast cancer

The taxanes docetaxel (Taxotere; Aventis Pharmaceuticals Inc., Bridgewater, NJ, http://www.aventispharma-us.com) and paclitaxel (Taxol; Bristol-Myers Squibb, Princeton, NJ, http://www.bms.com) have significant clinical activity in metastatic breast cancer. A number of clinical trials have evaluated the tolerability and efficacy of weekly taxane administration to optimize the benefit-to-risk ratio in metastatic breast cancer. Single-agent studies with docetaxel and paclitaxel in metastatic breast cancer show clinically significant antitumor activity even in advanced, heavily pretreated, resistant, and/or refractory disease. This activity is also evident with taxane-based combination regimens. Severe hematologic and nonhematologic toxicities are infrequent, with other toxicities noted based on the dose and weekly regimen selected. Weekly docetaxel and paclitaxel regimens represent valuable therapeutic options for women with metastatic breast cancer and have entered evaluation as part of adjuvant therapy for this disease.