Systemic therapy

Possible clinical cure of metastatic breast cancer: lessons from our 30-year experience with oligometastatic breast cancer patients and literature review

BACKGROUND

Metastatic breast cancer (MBC) is generally incurable. However, 10-20-year relapse-free survival of MBC is approximately 2%, implying that at least a small subset of MBC patients achieve prolonged survival. We therefore analyzed long-term outcome in a particular subset, i.e., oligometastatic breast cancer (OMBC).

METHODS

Data of OMBC subjects (N = 75) treated in our institution from April 1980 to March 2010 were retrospectively analyzed. OMBC was identified as: one or 2 organs involved with metastatic lesions (excluding the primary lesion resectable by surgery), fewer than 5 lesions per metastasized organ, and lesion diameter less than 5 cm. Patients were generally treated with systemic chemotherapy first, and those who achieved complete response (CR) or partial response (PR) were further treated, if applicable, with local therapy (surgical or radiation therapy) to maintain CR or to induce no evidence of clinical disease (NED), with additional systemic therapy.

RESULTS

Median follow-up duration was 103 (6-329) months. Single or 2 organs were involved in, respectively, 44 (59%) and 31 (41%) cases with metastatic lesions, 48% of which were visceral. In cases where effects of systemic therapy, possibly in combination with other treatments, were evaluated (N = 68), CR or PR was achieved in 33 (48.5%) or 32 (47.1%), respectively, with overall response rate (ORR: CR + PR) of 95.6% (N = 65). In cases receiving multidisciplinary treatment (N = 75), CR or NED (CR/NED), or PR was induced in 48 (64.0%) or 23 (30.7%) cases, respectively, with ORR (CR/NED + PR) of 94.7% (N = 71). CR rates (60.5%) with systemic therapy and CR/NED rates (79.5%) with multidisciplinary treatment were significantly better in subjects with a single involved organ than in those with two involved organs (P = 0.047 and 0.002, systemic only or multidisciplinary treatments, respectively). Medians estimated by Kaplan-Meier method were: overall survival (OS) of 185.0 months and relapse-free interval (RFI) of 48.0 months. Estimated outcomes were: OS rates (OSR) of 59.2% at 10 years and 34.1% at 20 years, and relapse-free rates (RFR) of 27.4% at 10 years and 20 years. No disease progression was observed after 101.0 months as RFR. Cases with single organ involvement (N = 44) showed significantly better outcomes (OSR of 73% at 10 years and 52% at 20 years, RFR of 42% at 10 years and 20 years). Those who received local therapies (N = 35) also showed better prognosis: OSR of 82% at 10 years and 53% at 20 years, RFR of 38% at 10 years and 20 years. Three cases (4%) survived for their lifetime without relapse after achieving CR or NED, our definition of clinical cure. Multivariate analysis revealed factors favoring better prognosis as: none for OS, and single organ involvement with metastasis, administration of local treatment, and shorter disease-free interval (DFI) (P = 0.030, 0.039, and 0.042, respectively) for RFR. Outcomes in OMBC in literature were OSR of 35-73% at 10 years and 26-52% at 20 years, and RFR of 27-42% at 10 years and 26-42% at 20 years.

CONCLUSIONS

The present analyses clearly indicate that OMBC is a distinct subgroup with long-term prognosis superior to MBC, with reasonable provability for clinical cure. Further prospective studies to better characterize OMBC are warranted to improve prognosis in MBC.

Population pharmacokinetic analysis of letrozole in Japanese postmenopausal women

PURPOSE

Letrozole is an orally active aromatase inhibitor for the treatment of breast cancer. The objectives of this study were to examine the pharmacokinetic profile of letrozole in Japanese subjects and to identify factors that influence variability in the pharmacokinetics of letrozole using population pharmacokinetic (PPK) analysis.

METHODS

Twenty-five healthy postmenopausal Japanese women were enrolled in the study and received 2.5 mg letrozole once daily for 14 or 28 days. A PPK model was developed using NONMEM software. Age, body weight (WT), AST, ALT, total bilirubin, serum creatinine (CRE), and genotype of CYP2A6 were studied as covariates. Estrone, estrone sulfate, and estradiol in plasma were measured as pharmacodynamic markers.

RESULTS

CYP2A6 genotype, CRE, and AST were significant covariates for apparent systemic clearance (CL/F), and WT was a significant covariate for apparent distribution volume (Vd/F). Population mean estimates of CL/F and Vd/F in subjects without CYP2A6 mutation were 1.03 × (CRE/0.70)(-1.27) × (AST/17.5)(-0.793) L/h and 94.2 × (WT/51.1)(1.12) L respectively. CL/F in subjects possessing 1 and 2 CYP2A6 mutation alleles were 84.3% and 44.8% of the value in the subjects without mutation respectively. Estrogen levels fell to below detection limits in most subjects after letrozole administration. Three mild and transient adverse events (upper respiratory tract inflammation, arthralgia, and vomiting) were reported in the study.

CONCLUSIONS

CYP2A6 genotype largely influences CL/F of letrozole. Genetic polymorphism of CYP2A6 and body weight will be causes of ethnic difference in PK. However, dose adjustment is not necessary, because of the wide therapeutic range.

Pharmacodiagnostic testing in breast cancer: focus on HER2 and trastuzumab therapy

Pharmacogenomics is defined as research into inherited genetic variations that determine an individual's response to therapeutic agents. In oncology, pharmacogenomics based on somatic molecular alterations inherited by subsequent cancer cell generations forms the basis of molecular targeting of novel therapeutic agents. What has emerged from clinical experience with such agents is the need for appropriate pharmacodiagnostic approaches to ensure the drugs are correctly targeted. Given the broad range of pharmacogenomic agents currently under evaluation for cancer therapy, it appears that a rapid extension of pharmacodiagnostic profiling will be required in the next 5-10 years, if not sooner. If this is to be successfully achieved, lessons learned in the past, particularly during the development of HER2 (ERBB2) testing for directing trastuzumab therapy in breast cancer, may provide a valuable framework for the development of future pharmacodiagnostic assays system. This article reviews the biological and clinical rationale for targeting breast cancer with trastuzumab and the steps taken to validate and improve pharmacodiagnostic procedures for testing tumor HER2 protein expression and HER2 gene amplification. Attention is given to quality assurance and reproducibility of testing approaches and the optimal selection of patients for response to trastuzumab. This approach serves as a paradigm for the future development of pharmacodiagnostic tests in oncology.

The planetary biology of cytochrome P450 aromatases

Background

Joining a model for the molecular evolution of a protein family to the paleontological and geological records (geobiology), and then to the chemical structures of substrates, products, and protein folds, is emerging as a broad strategy for generating hypotheses concerning function in a post-genomic world. This strategy expands systems biology to a planetary context, necessary for a notion of fitness to underlie (as it must) any discussion of function within a biomolecular system.

Results

Here, we report an example of such an expansion, where tools from planetary biology were used to analyze three genes from the pig Sus scrofa that encode cytochrome P450 aromatases–enzymes that convert androgens into estrogens. The evolutionary history of the vertebrate aromatase gene family was reconstructed. Transition redundant exchange silent substitution metrics were used to interpolate dates for the divergence of family members, the paleontological record was consulted to identify changes in physiology that correlated in time with the change in molecular behavior, and new aromatase sequences from peccary were obtained. Metrics that detect changing function in proteins were then applied, including K_A/K_S values and those that exploit structural biology. These identified specific amino acid replacements that were associated with changing substrate and product specificity during the time of presumed adaptive change. The combined analysis suggests that aromatase paralogs arose in pigs as a result of selection for Suoidea with larger litters than their ancestors, and permitted the Suoidea to survive the global climatic trauma that began in the Eocene.

Conclusions

This combination of bioinformatics analysis, molecular evolution, paleontology, cladistics, global climatology, structural biology, and organic chemistry serves as a paradigm in planetary biology. As the geological, paleontological, and genomic records improve, this approach should become widely useful to make systems biology statements about high-level function for biomolecular systems.