Biologic basis and evolving role of aromatase inhibitors in the management of invasive carcinoma of the breast

Goserelin plus letrozole as first- or second-line hormonal treatment in premenopausal patients with advanced breast cancer

A promising new option as the treatment of choice for premenopausal patients with metastatic breast cancer (MBC) could be the combination of a luteinising hormone-releasing hormone analog and an aromatase inhibitor. Very little data about the use of goserelin with anastrozole in advanced breast cancer are available, and no cohort studies on the efficacy of goserelin with letrozole in advanced premenopausal breast cancer patients have been reported. We present the single-centre, retrospective, experience of goserelin plus letrozole in a total of 52 premenopausal women with MBC. All patients received goserelin 3.6 mg by subcutaneous injection every 4 weeks along with letrozole 2.5 mg daily as first-line (n=36) and second-line (n=16) hormonal treatment. The median duration of goserelin with letrozole treatment was 11 (range, 2-61) months, and the median duration of overall follow-up was 31 (range, 3-66) months. The objective response rate (ORR) was 21.1%, with two complete response (CR) (3.8%) and nine partial response (PR) (17.3%). Stable disease (SD) lasting more than 6 months was achieved by 26 patients (50.0%). Thus, goserelin with letrozole conferred clinical benefit (CB) in 37 women (71.1%). The progression-free survival (PFS) was 10 months. CR was exclusively observed in hormone receptor-double-positive patients. Drug therapy was well tolerated; no grade 3/4 toxicities were reported. Goserelin plus letrozole appears to be an efficacious and well-tolerated regimen in women with advanced breast cancer. Further prospectively randomized studies involving more patients and longer follow-up are indicated.

Tumor receptor imaging

Tumor receptors play an important role in carcinogenesis and tumor growth and have been some of the earliest targets for tumor-specific therapy, for example, the estrogen receptor in breast cancer. Knowledge of receptor expression is key for therapy directed at tumor receptors and traditionally has been obtained by assay of biopsy material. Tumor receptor imaging offers complementary information that includes evaluation of the entire tumor burden and characterization of the heterogeneity of tumor receptor expression. The nature of the ligand-receptor interaction poses a challenge for imaging--notably, the requirement for a low molecular concentration of the imaging probe to avoid saturating the receptor and increasing the background because of nonspecific uptake. For this reason, much of the work to date in tumor receptor imaging has been done with radionuclide probes. In this overview of tumor receptor imaging, aspects of receptor biochemistry and biology that underlie tumor receptor imaging are reviewed, with the estrogen-estrogen receptor system in breast cancer as an illustrative example. Examples of progress in radionuclide receptor imaging for 3 receptor systems--steroid receptors, somatostatin receptors, and growth factor receptors-are highlighted, and recent investigations of receptor imaging with other molecular imaging modalities are reviewed.

Physician recommendations regarding tamoxifen and patient utilization of tamoxifen after surgery for ductal carcinoma in situ

BACKGROUND

To date, the impact of the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-24 trial reported in 1999 on the use of tamoxifen after surgery for ductal carcinoma in situ (DCIS) is unknown. The current study was designed to evaluate the impact of NSABP B-24 on current practices at a comprehensive cancer center.

METHODS

The records of 350 consecutive patients with DCIS who were treated at the authors' institution between July 1999 and June 2002 were obtained from a prospective database and analyzed. Whether patients were offered tamoxifen, whether patients accepted tamoxifen, and the associated reasons were recorded along with tamoxifen-related side effects and patient compliance with therapy. Clinical and pathologic factors were evaluated for their impact on recommendations regarding tamoxifen. Differences were assessed by chi-square analysis.

RESULTS

Of the 350 patients, 73 were excluded because of evidence of invasive carcinoma on final pathology review. Of the remaining 277 patients, 166 patients (60%) were offered tamoxifen, and 90 patients (54%) chose to take tamoxifen. Of 111 patients who were not offered tamoxifen, 39 patients (35%) had documented explanations, which included bilateral mastectomy (n = 25 patients), medical reasons (n = 10 patients), and already received tamoxifen for other reasons at the time of diagnosis (n = 4 patients). Of 94 patients who received tamoxifen, 20 patients (21%) discontinued use because of side effects or complications. Tamoxifen was more likely to be recommended for women who underwent segmental resection compared with women who underwent total mastectomy (P = 0.002) and for women with smaller pathologic DCIS tumors (P = 0.001). In addition, these two factors were interrelated.

CONCLUSIONS

Physicians and patients remain cautious regarding the use of tamoxifen after local treatment for DCIS. The current findings have implications for current trials evaluating aromatase inhibitors and other chemopreventive agents for this disease.

Fulvestrant (Faslodex) versus anastrozole for the second-line treatment of advanced breast cancer in subgroups of postmenopausal women with visceral and non-visceral metastases: combined results from two multicentre trials

The efficacy of fulvestrant (Faslodex), a novel oestrogen receptor (ER) antagonist that downregulates the ER and has no known agonist effects, was compared with the aromatase inhibitor anastrozole (Arimidex) for the second-line treatment of advanced breast cancer in postmenopausal women with visceral and non-visceral metastases. Assessment was by means of a retrospective subgroup analysis of combined data from two randomised, phase III trials. Objective response (OR) rates were similar in patients treated with fulvestrant and anastrozole, respectively (21.9% versus 19.3%-patients with no visceral metastases; 15.7% versus 13.2%-all of the patients with visceral metastases; 18.8% versus 14.0%-patients with visceral metastases only). The proportion of patients with clinical benefit (CB) was also similar between treatments and between subgroups with and without visceral disease. Fulvestrant is at least as effective as anastrozole, providing a valuable treatment option for advanced breast cancer in postmenopausal women with visceral metastases who have failed on prior endocrine therapy.

A stochastic economic evaluation of letrozole versus tamoxifen as a first-line hormonal therapy: for advanced breast cancer in postmenopausal patients

BACKGROUND

Letrozole is a third-generation aromatase inhibitor that is a feasible alternative to tamoxifen as a first-line hormonal therapy for patients with advanced breast cancer.

OBJECTIVE

This paper presents the results of an economic evaluation comparing letrozole and tamoxifen as first-line hormonal therapies in postmenopausal women diagnosed with advanced breast cancer.

PERSPECTIVE

UK National Health Service.

DESIGN

A decision model (Markov process) was built describing possible patient pathways from the point of diagnosis to death. The model was populated using patient-specific clinical trial data, data from the existing literature, and expert opinion. Stochastic analyses of the model were undertaken, whereby the majority of the input parameters were described as probability distributions to represent the uncertainty about their true value. Costs were presented in year 2000 values.

RESULTS

The baseline results showed that letrozole is a cost-effective alternative to tamoxifen with a mean incremental cost per life-year gained of pound 2342, whilst the incremental cost increases to just over pound 10,000 at the 95th percentile of the cost-effectiveness range (2000 values).

CONCLUSIONS

The results of the economic analysis indicate that letrozole is a cost-effective alternative first-line therapy compared with tamoxifen for postmenopausal women with advanced breast cancer, achieving additional life-years with a modest increase in costs.

Pre-clinical applications of transgenic mouse mammary cancer models

Breast cancer is a leading cause of cancer morbidity and mortality. Given that the majority of human breast cancers appear to be due to non-genetic factors, identifying agents and mechanisms of prevention is key to lowering the incidence of cancer. Genetically engineered mouse models of mammary cancer have been important in elucidating molecular pathways and signaling events associated with the initiation, promotion, and the progression of cancer. Since several transgenic mammary models of human breast cancer progress through well-defined cancer stages, they are useful pre-clinical systems to test the efficacy of chemopreventive and chemotherapeutic agents. This review outlines several oncogenic pathways through which mammary cancer can be induced in transgenic models and describes several types of preventive and therapeutic agents that have been tested in transgenic models of mammary cancer. The effectiveness of farnesyl inhibitors, aromatase inhibitors, differentiating agents, polyamine inhibitors, anti-angiogenic inhibitors, and immunotherapeutic compounds including vaccines have been evaluated in reducing mammary cancer and tumor progression in transgenic models.

Genome-wide search for markers associated with bovine spongiform encephalopathy

A genome-wide search for markers associated with BSE incidence was performed by using Transmission-Disequilibrium Tests (TDTs). Significant segregation distortion, i.e., unequal transmission probabilities of alleles within a locus, was found for three marker loci on Chromosomes (Chrs) 5, 10, and 20. Although TDTs are robust to false associations owing to hidden population substructures, it cannot distinguish segregation distortion caused by a true association between a marker and bovine spongiform encephalopathy (BSE) from a population-wide distortion. An interaction test and a segregation distortion analysis in half-sib controls were used to disentangle these two alternative hypotheses. None of the markers showed any significant interaction between allele transmission rates and disease status, and only the marker on Chr 10 showed a significant segregation distortion in control individuals. Nevertheless, the control group may have been a mixture of resistant and susceptible but unchallenged individuals. When new genotypes were generated in the vicinity of these three markers, evidence for an association with BSE was confirmed for the locus on Chr 5.