Idoxifene antagonism of oestradiol-dependent MCF-7 breast cancer xenograft growth

Phase III Double-Blind Trial of Arzoxifene Compared With Tamoxifen for Locally Advanced or Metastatic Breast Cancer

Purpose

To compare the efficacy of arzoxifene with tamoxifen for the treatment of locally advanced or metastatic breast cancer.

Patients and Methods

Women with estrogen- or progesterone-receptor–positive breast cancer who had not received prior systemic therapy, or who had relapsed more than 12 months after stopping adjuvant hormonal therapy, were randomly assigned to receive 20 mg arzoxifene or 20 mg tamoxifen daily. Each treatment arm was to have 240 patients enrolled. The primary end point was progression-free survival. Secondary end points included other measures of tumor response, overall survival, and safety.

Results

Enrollment was stopped when a planned interim analysis of the first 200 patients suggested arzoxifene to be significantly inferior to tamoxifen. The median progression-free survival for the 352 patients who had been randomly assigned when enrollment was stopped was 4.0 months (95% CI, 3.4 to 5.6 months) for the arzoxifene group and 7.5 months (95% CI, 5.9 to 8.8 months) for the tamoxifen group. On-study progression-free survival (P = .011) and time to treatment failure (P = .029) also favored tamoxifen. Overall tumor response rate and median response duration were comparable between the groups. Adverse events were similar between the treatments, except for nausea (more frequent with arzoxifene) and vaginal discharge (more frequent with tamoxifen).

Conclusion

Tamoxifen produced significantly longer progression-free survival and time to treatment failure compared with arzoxifene in the treatment of locally advanced and metastatic breast cancer. There were no significant differences between tumor response rate, clinical benefit rate, or median response duration.

Proliferation marker Ki-67 in early breast cancer

Molecular markers have been extensively investigated with a view to providing early and accurate information on long-term outcome and prediction of response to treatment of early breast cancer. Proliferation is a key feature of the progression of tumors and is now widely estimated by the immunohistochemical assessment of the nuclear antigen Ki-67. The expression of Ki-67 correlates with other measurements of proliferation, including S-phase and bromodeoxyuridine uptake. High Ki-67 is a sign of poor prognosis associated with a good chance of clinical response to chemotherapy, but its independent significance is modest and does not merit measurements in most routine clinical scenarios. However, its application as a pharmacodynamic intermediate marker of the effectiveness of medical therapy holds great promise for rapid evaluation of new drugs.

Biomarker Changes During Neoadjuvant Anastrozole, Tamoxifen, or the Combination: Influence of Hormonal Status and HER-2 in Breast Cancer—A Study from the IMPACT Trialists

Purpose

To investigate the relationships between biomarker changes in breast cancer during neoadjuvant (preoperative) endocrine therapy.

Patients and Methods

The IMPACT trial compared the preoperative use of tamoxifen with anastrozole alone or in combination in postmenopausal women (n = 330) with primary breast cancer. Biomarkers were measured in tumor biopsy specimens taken at baseline, and after 2 and 12 weeks of treatment.

Results

A decrease in the proliferation marker Ki67 occurred in the majority of patients: 52 (93%) of 56, 46 (85%) of 54, and 37 (84%) of 44 patients in the anastrozole, tamoxifen, and combination groups, respectively. There was a significantly greater suppression of Ki67 in the anastrozole-treated group than in the tamoxifen- or combination-treated groups, which is parallel to the greater efficacy seen for anastrozole over these two treatments in the Arimidex, Tamoxifen, Alone or in Combination adjuvant trial. A positive relationship was noted between estrogen-receptor level and Ki67 suppression in all patients. Ki67 was reduced to a greater extent in progesterone receptor-positive tumors compared with progesterone receptor-negative tumors. HER-2-negative tumors tended to show a greater reduction in Ki67 compared with HER-2-positive tumors, but the difference was only significant in the tamoxifen group after 2 weeks, and in the anastrozole group after 12 weeks.

Conclusion

These results confirm the value of Ki67 as a molecular marker, and provide information regarding the relationships between treatment-induced changes in Ki67 and other important biomarkers. Studies such as this should help integrate agents targeted at growth factor signaling with endocrine agents in breast cancer.

Molecular changes in tamoxifen-resistant breast cancer: relationship between estrogen receptor, HER-2, and p38 mitogen-activated protein kinase

PURPOSE

To evaluate growth factor receptor cross talk with the estrogen receptor (ER) in paired clinical breast cancer specimens and in a xenograft model before tamoxifen and at tumor progression as a possible mechanism for tamoxifen resistance.

METHODS

Specimen pairs from 39 patients were tissue arrayed and stained for ER, progesterone receptor (PgR), Bcl-2, c-ErbB2 (HER-2), and phosphorylated (p) p38 mitogen-activated protein kinase (MAPK), p-ERK1/2 MAPK, and p-Akt. Xenograft MCF-7 tumors before and after tamoxifen resistance were assessed for levels of p-p38.

RESULTS

Pretreatment, there were strong correlations between ER, PgR, and Bcl-2, and an inverse correlation between ER and HER-2. These correlations were lost in the tamoxifen- resistant tumors and replaced by strong correlations between ER and p-p38 and p-ERK. ER expression was lost in 17% of resistant tumors. Three (11%) of the 26 tumors originally negative for HER-2 became amplified and/or overexpressed at resistance. All ER-positive tumors that overexpressed HER-2 originally or at resistance expressed high levels of p-p38. In the pretreatment and tamoxifen-resistant specimens, there were strong correlations between p-p38 and p-ERK. In the tamoxifen-resistant xenograft tumors, like the clinical samples, there was a striking increase in p-p38.

CONCLUSION

The molecular pathways driving tumor growth can change as the tumor progresses. Crosstalk between ER, HER-2, p38, and ERK may contribute to tamoxifen resistance and may provide molecular targets to overcome this resistance.

Short-Term Changes in Ki-67 during Neoadjuvant Treatment of Primary Breast Cancer with Anastrozole or Tamoxifen Alone or Combined Correlate with Recurrence-Free Survival

Purpose: Neoadjuvant (preoperative) therapy for breast cancer may allow for the development of intermediate markers of treatment benefit, thereby circumventing the need for efficacy trials of adjuvant therapy, which require much larger patient numbers and longer follow-up. The aim of this study—as part of the Immediate Preoperative “Arimidex” (anastrozole), Tamoxifen, or Arimidex Combined with Tamoxifen (IMPACT) trial (n = 330)—was to test the hypotheses that changes in Ki-67 after 2 weeks and/or 12 weeks: (i) differed between treatments, (ii) predicted clinical tumor response, and/or (iii) may predict long-term outcome differences between treatments in adjuvant therapy.

Experimental Design: The Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial compared these same agents in the adjuvant setting. Biomarkers were measured in biopsy specimens taken before and after 2 and 12 weeks of treatment.

Results: Suppression of the proliferation marker Ki-67 after 2 and 12 weeks was significantly greater with anastrozole than with tamoxifen (P = 0.004 and P < 0.001) but was similar between tamoxifen and the combination (P = 0.600 and P = 0.912). This result closely parallels that seen for the relative recurrence-free survival with the treatments after a median follow-up of 31 months in the ATAC trial in 9,366 patients. Against expectations, apoptosis was not increased in any of the treatment arms.

Conclusions: The data indicate that short-term changes in proliferation in the neoadjuvant setting may be able to predict outcome during adjuvant use of the same treatments. If this can be confirmed, these findings could lead to a profound change in approaches to drug development in breast cancer. The data indicate that estrogen is not an important survival factor for human breast cancer cells.

Comparison of the systemic and intratumoral effects of tamoxifen and the aromatase inhibitor vorozole in postmenopausal patients with primary breast cancer

PURPOSE

To determine biologic differences, if any, between presurgical endocrine treatment with an aromatase inhibitor (vorozole) and tamoxifen in patients with postmenopausal primary breast cancer.

PATIENTS AND METHODS

Randomization was to 12 weeks of 2.5 mg of vorozole per day or 20 mg of tamoxifen per day, both orally. Clinical response was assessed monthly together with serum sex hormone binding globulin (SHBG), luteinizing hormone (LH), follicle-stimulating hormone (FSH), estrogens (E1, E2, and E1S), lipids, insulin-like growth factor-1 (IGF-1), and bone metabolites (CrossLaps CTx). Tissue samples for Ki67, apoptotic index (AI), estrogen receptor, and progesterone receptor were collected at 0, 2, and 12 weeks.

RESULTS

Ki67 fell by 58% and 43% (means) at 2 weeks in the vorozole and tamoxifen patients, respectively (P =.13). In the vorozole group, the correlations of proportional changes in Ki67 at 2 weeks with tumor volume changes and clinical response at 12 weeks were not significant (P =.09) and marginally significant (P =.04), respectively. Serum lipids did not differ between groups. Serum levels of EI, E2, and E1S were suppressed markedly by vorozole, whereas levels of SHBG increased and LH and FSH fell significantly with tamoxifen. IGF-1 levels fell significantly with tamoxifen (P =.001) compared with the nonsignificant rise with vorozole. Twelve-week CTx values fell by 19% with tamoxifen (P =.006) and rose by 11% with vorozole (P =.15).

CONCLUSION

The correlation with vorozole of Ki67 with volume and clinical response supports this as an intermediate marker. The nonsignificant effects on bone and lipid metabolism by the aromatase inhibitor may be important to consider for adjuvant and potential prevention strategies.

The evidence-based use of induction chemotherapy in breast cancer

The use of induction chemotherapy, also known as pre-operative or neoadjuvant chemotherapy has been studied in a number of randomised trials. Response rates are generally high, ranging from 70-90%, which allows for the downstaging of primary tumours and breast conservation surgery. Conserving surgery as opposed to mastectomy in this setting appears to be safe, effective and improves quality of life, although there is a suggestion of a small increase in local recurrence rate. Data from the randomised trials presented in this review shows that the use of induction chemotherapy neither prolongs nor decreases overall or disease free survival when compared with the same chemotherapy given in an adjuvant setting. There is a direct correlation between response of a primary breast tumour to induction chemotherapy and patient outcome, probably because this approximates the effect of induction chemotherapy on micrometastases which are present at presentation in many patients with apparently localised primary breast cancers. A pathological complete response after surgery is an excellent predictor of long term outcome, and is more likely to be seen in smaller tumours. Induction chemotherapy can be used as an in vivo measure of tumour response to treatment. This allows a further option of switching cytotoxic drugs in apparently resistant tumours.

Selective estrogen receptor modulators: structure, function, and clinical use

The sex hormone estrogen is important for many physiologic processes. Prolonged stimulation of breast ductal epithelium by estrogen, however, can contribute to the development and progression of breast cancer, and treatments designed to block estrogen's effects are important options in the clinic. Tamoxifen and other similar drugs are effective in breast cancer prevention and treatment by inhibiting the proliferative effects of estrogen that are mediated through the estrogen receptor (ER). However, these drugs also have many estrogenic effects depending on the tissue and gene, and they are more appropriately called selective estrogen receptor modulators (SERMs). SERMs bind ER, alter receptor conformation, and facilitate binding of coregulatory proteins that activate or repress transcriptional activation of estrogen target genes. Theoretically, SERMs could be synthesized that would exhibit nearly complete agonist activity on the one hand or pure antiestrogenic activity on the other. Depending on their functional activities, SERMs could then be developed for a variety of clinical uses, including prevention and treatment of osteoporosis, treatment and prevention of estrogen-regulated malignancies, and even for hormone replacement therapy. Tamoxifen is effective in patients with ER-positive metastatic breast cancer and in the adjuvant setting. The promising role for tamoxifen in ductal carcinoma-in-situ or for breast cancer prevention is evolving, and its use can be considered in certain patient groups. Other SERMs are in development, with the goal of reducing toxicity and/or improving efficacy, and future agents have the potential of providing a new paradigm for maintaining the health of women.