Antagonism between tamoxifen and doxorubicin in the MCF-7 human breast tumor cell line

Long-Term Outcomes with Pharmacological Ovarian Suppression during Chemotherapy in Premenopausal Early Breast Cancer Patients

BACKGROUND

Although use of gonadotropin-releasing hormone agonist (GnRHa) during chemotherapy is an established strategy to protect ovarian function in premenopausal breast cancer patients, no long-term safety data are available raising some concerns in women with hormone receptor-positive disease. There are controversial data on its fertility preservation potential.

METHODS

The PROMISE-GIM6 is a multicenter, randomized, open-label, phase III superiority trial conducted at 16 Italian centers from October 2003 to January 2008. Eligible patients were randomized to (neo)adjuvant chemotherapy alone (control arm) or combined with the GnRHa triptorelin (GnRHa arm). Primary planned endpoint was incidence of chemotherapy-induced premature ovarian insufficiency (POI). Post-hoc endpoints were disease-free survival (DFS), overall survival (OS), and post-treatment pregnancies. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated.

RESULTS

Of 281 randomized patients, 80.4% had hormone receptor-positive breast cancer. Median follow-up was 12.4 years (interquartile range = 11.3-13.2 years). No differences in 12-year DFS (65.7% [95% CI = 57.0% to 73.1%] in GnRHa arm vs. 69.2% [95% CI = 60.3% to 76.5%] in control arm; HR = 1.16, 95% CI = 0.76 to 1.77) nor in 12-year OS (81.2% [95% CI = 73.6% to 86.8%] in GnRHa arm vs. 81.3% [95% CI = 73.1% to 87.2%] in control arm; HR = 1.17, 95% CI = 0.67 to 2.03) were observed. In patients with hormone receptor-positive disease, the HR was 1.02 (95% CI = 0.63 to 1.63) for DFS and 1.12 (95% CI = 0.59 to 2.11) for OS. In the GnRHa and control arms, 9 and 4 patients had a post-treatment pregnancy, respectively (HR = 2.14, 95% CI = 0.66 to 6.92).

CONCLUSIONS

Final analysis of the PROMISE-GIM6 trial provides reassuring results on the safety of GnRHa use during chemotherapy as a strategy to preserve ovarian function in premenopausal patients with early breast cancer, including those with hormone receptor-positive disease.

The role of gonadotropin-releasing hormone agonists in female fertility preservation

Advances in anticancer treatments have resulted in increasing survival rates among cancer patients. Accordingly, the quality of life after treatment, particularly the preservation of fertility, has gradually emerged as an essential consideration. Cryopreservation of embryos or unfertilized oocytes has been considered as the standard method of fertility preservation among young women facing gonadotoxic chemotherapy. Other methods, including ovarian suppression and ovarian tissue cryopreservation, have been considered experimental. Recent large-scale randomized controlled trials have demonstrated that temporary ovarian suppression using gonadotropin-releasing hormone agonists (GnRHa) during chemotherapy is beneficial for preventing chemotherapy-induced premature ovarian insufficiency in breast cancer patients. It should also be emphasized that GnRHa use during chemotherapy does not replace established fertility preservation methods. All young women facing gonadotoxic chemotherapy should be counseled about and offered various options for fertility preservation, including both GnRHa use and cryopreservation of embryos, oocytes, and/or ovarian tissue.

Synthesis and In Vitro Evaluation of Tetrahydroquinoline Derivatives as Antiproliferative Compounds of Breast Cancer via Targeting the GPER

BACKGROUND

Some reports have demonstrated the role of the G Protein-coupled Estrogen Receptor (GPER) in growth and proliferation of breast cancer cells.

OBJECTIVE

In an effort to develop new therapeutic strategies against breast cancer, we employed an in silico study to explore the binding modes of tetrahydroquinoline 2 and 4 to be compared with the reported ligands G1 and G1PABA.

METHODS

This study aimed to design and filter ligands by in silico studies determining their Lipinski's rule, toxicity and binding properties with GPER to achieve experimental assays as anti-proliferative compounds of breast cancer cell lines.

RESULTS

In silico studies suggest as promissory two tetrahydroquinoline 2 and 4 which contain a carboxyl group instead of the acetyl group (as is needed for G1 synthesis), which add low (2) and high hindrance (4) chemical moieties to explore the polar, hydrophobic and hindrance effects. Docking and molecular dynamics simulations of the target compounds were performed with GPER to explore their binding mode and free energy values. In addition, the target small molecules were synthesized and assayed in vitro using breast cancer cells (MCF-7 and MDA-MB-231). Experimental assays showed that compound 2 decreased cell proliferation, showing IC50 values of 50µM and 25µM after 72h of treatment of MCF-7 and MDA-MB-231 cell lines, respectively. Importantly, compound 2 showed a similar inhibitory effect on proliferation as G1 compound in MDA-MB-231 cells, suggesting that both ligands reach the GPER-binding site in a similar way, as was demonstrated through in silico studies.

CONCLUSION

A concentration-dependent inhibition of cell proliferation occurred with compound 2 in the two cell lines regardless of GPER.

Cancer Targeting and Drug Delivery Using Carbon-Based Quantum Dots and Nanotubes

Currently cancer treatment is in large part non-specific with respect to treatment. Medication is often harsh on patients, whereby they suffer several undesired side effects as a result. Carbon-based nanoparticles have attracted attention in recent years due to their ability to act as a platform for the attachment of several drugs and/or ligands. Relatively simple models are often used in cancer research, wherein carbon nanoparticles are conjugated to a ligand that is specific to an overexpressed receptor for imaging and drug delivery in cancer treatment. These carbon nanoparticles confer unique properties to the imaging or delivery vehicle due to their nontoxic nature and their high fluorescence qualities. Chief among the ongoing research within carbon-based nanoparticles emerge carbon dots (C-dots) and carbon nanotubes (CNTs). In this review, the aforementioned carbon nanoparticles will be discussed in their use within doxorubicin and gemcitabine based drug delivery vehicles, as well as the ligand-mediated receptor specific targeted therapy. Further directions of research in current field are also discussed.

A preliminary study of 18F-FES PET/CT in predicting metastatic breast cancer in patients receiving docetaxel or fulvestrant with docetaxel

The present explorative study was initiated to evaluate the clinical value of ¹⁸F-FES PET/CT in monitoring the change of estrogen receptor (ER) expression and potential predictive value in metastatic breast cancer patients. Twenty-two pathology-confirmed breast cancer patients were prospectively enrolled and randomly divided into two groups (T: docetaxel, n = 14 and TF: docetaxel + fulvestrant, n = 8). The percentage of patients without disease progression after 12 months (PFS > 12 months) was 62.5% in group TF compared with 21.4% in group T (P = 0.08). According to ¹⁸F-FES PET/CT scans, the SUVmax (maximum standard uptake value) of all the metastatic lesions decreased in group TF after 2 cycles of treatment (6 weeks ± 3 days). However, 6 of 9 patients in group T had at least one lesion with higher post-treatment SUVmax. There was a significant difference in the reduction of ER expression between these two groups (P = 0.028). In group TF, the patients with PFS > 12 months had significantly greater SUVmax changes of ¹⁸F-FES than those with PFS < 12 months (PFS > 12 months: 91.0 ± 12.0% versus PFS < 12 months: 20.7 ± 16.2%; t = −4.64, P = 0.01). Our preliminary study showed that ¹⁸F-FES PET/CT, as a noninvasive method to monitor ER expression, could be utilized to predict prognosis based on changes in SUVmax.

Chemosensitization role of fulvestrant in combination with chemotherapy in postmenopausal hormone receptor positive and human epidermal growth factor negative metastatic breast cancer

In metastatic breast cancer (MBC), hormone receptor positive (HR+), human epidermal growth factor negative (HER2-) subtype accounts for the majority. With various new modalities available to prolong life span in this group of patients, the effect is distant from optimum. Prevalent strategy of treating postmenopausal HR+ HER2- MBC is application of chemotherapy (CT) after progression of disease on endocrine therapy (ET) of several lines. Generally, ET targets HR+ ingredients and CT works better with HR- tumor cells. HR+ MBC, though hormone-sensitive, has HR- portion which reacts poorly to ET. Thus, sequential use of ET and CT neglects its insensitive part and gives rise to drug resistance, while alleviation of tumor burden is the top priority in metastatic setting. Chemohormonal therapy (i.e. concomitant use of ET and chemotherapy) complements for the shortcoming of current therapy strategy targeting both HR+ and HR- ingredients theoretically. Fulvestrant, a pure estrogen receptor antagonist and down-regulator, could be a promising agent using concurrently with CT based on chemosensitizing character shown in preclinical and pilot clinical studies. It is hypothesized in this article that chemohormonal therapy with concurrent fulvestrant and CT would be a promising strategy in postmenopausal HR+ HER2- MBC patients. Proof of this hypothesis would help control evolvement of tumor burden and acquirement of drug resistance over a short period of time.

Combinatorial Cytotoxic Effects of Damnacanthal and Doxorubicin against Human Breast Cancer MCF-7 Cells in Vitro

Despite progressive research being done on drug therapy to treat breast cancer, the number of patients succumbing to the disease is still a major issue. Combinatorial treatment using different drugs and herbs to treat cancer patients is of major interest in scientists nowadays. Doxorubicin is one of the most used drugs to treat breast cancer patients. The combination of doxorubicin to other drugs such as tamoxifen has been reported. Nevertheless, the combination of doxorubicin with a natural product-derived agent has not been studied yet. Morinda citrifolia has always been sought out for its remarkable remedies. Damnacanthal, an anthraquinone that can be extracted from the roots of Morinda citrifolia is a promising compound that possesses a variety of biological properties. This study aimed to study the therapeutic effects of damnacanthal in combination with doxorubicin in breast cancer cells. Collectively, the combination of both these molecules enhanced the efficacy of induced cell death in MCF-7 as evidenced by the MTT assay, cell cycle, annexin V and expression of apoptosis-related genes and proteins. The effectiveness of doxorubicin as an anti-cancer drug was increased upon addition of damnacanthal. These results could provide a promising approach to treat breast cancer patients.

Tamoxifen enhances the cytotoxicity of conventional chemotherapy in esophageal adenocarcinoma cells

INTRODUCTION

Esophageal adenocarcinoma is a lethal malignancy which is increasing in incidence, and many patients receive chemotherapy as part of their treatment. We have previously demonstrated that esophageal adenocarcinoma-derived cell lines respond to treatment with estrogen receptor modulators, such as tamoxifen. Reports from breast cancer suggest that tamoxifen may attenuate the efficacy of other chemotherapeutic agents. We have therefore assessed the response of esophageal adenocarcinoma cell lines to tamoxifen therapy when given in combination with conventional agents.

METHODS

Two estrogen receptor (ER)-positive esophageal adenocarcinoma cell lines (OE-19 and OE-33) were treated with combinations of tamoxifen, cisplatin and 5-fluorouracil (5-FU). Effects on cell viability were measured using an MTS assay, and cell death was detected with annexin V/propidium iodide flow cytometry. To assess whether the efficacy of tamoxifen in these cell lines might be relevant to the clinical setting, we analyzed ER status in 10 esophageal adenocarcinoma tissue specimens by immunohistochemistry.

RESULTS

IC50 values (μM) for OE-19 and OE-33 were 11.2 and 7.1 for tamoxifen, 19.6 and 4.7 for cisplatin, and 1.7 and 5.9 for 5-FU, respectively. Cell death was detected in 11.9% and 15.8% of cells treated with tamoxifen, 7.9% and 8.7% cells treated with cisplatin, and 3.6% and 8.6% cells treated with 5-FU at their IC50s. The addition of tamoxifen to cisplatin increased cell death by 11.4% in OE-19 (p < 0.0001) and 16.3% in OE-33 (p < 0.0001). Similarly, the addition of tamoxifen to 5-FU increased cell death by 11.6% in OE-19 (p < 0.0001) and 15.9% in OE-33 (p < 0.0001). Eight of 10 tissue specimens showed positive staining for ERα and 7 of 10 for ERβ.

CONCLUSIONS

In a cell culture model the addition of tamoxifen to conventional chemotherapy appears to be both feasible and beneficial. Expression of ERα and ERβ was also confirmed in esophageal adenocarcinoma tissues.

Ovarian suppression using luteinizing hormone-releasing hormone agonists during chemotherapy to preserve ovarian function and fertility of breast cancer patients: a meta-analysis of randomized studies

BACKGROUND

The role of temporary ovarian suppression with luteinizing hormone-releasing hormone agonists (LHRHa) in the prevention of chemotherapy-induced premature ovarian failure (POF) is still controversial. Our meta-analysis of randomized, controlled trials (RCTs) investigates whether the use of LHRHa during chemotherapy in premenopausal breast cancer patients reduces treatment-related POF rate, increases pregnancy rate, and impacts disease-free survival (DFS).

METHODS

A literature search using PubMed, Embase, and the Cochrane Library, and the proceedings of major conferences, was conducted up to 30 April 2015. Odds ratios (ORs) and 95% confidence intervals (CIs) for POF (i.e. POF by study definition, and POF defined as amenorrhea 1 year after chemotherapy completion) and for patients with pregnancy, as well hazard ratios (HRs) and 95% CI for DFS, were calculated for each trial. Pooled analysis was carried out using the fixed- and random-effects models.

RESULTS

A total of 12 RCTs were eligible including 1231 breast cancer patients. The use of LHRHa was associated with a significant reduced risk of POF (OR 0.36, 95% CI 0.23-0.57; P < 0.001), yet with significant heterogeneity (I(2) = 47.1%, Pheterogeneity = 0.026). In eight studies reporting amenorrhea rates 1 year after chemotherapy completion, the addition of LHRHa reduced the risk of POF (OR 0.55, 95% CI 0.41-0.73, P < 0.001) without heterogeneity (I(2) = 0.0%, Pheterogeneity = 0.936). In five studies reporting pregnancies, more patients treated with LHRHa achieved pregnancy (33 versus 19 women; OR 1.83, 95% CI 1.02-3.28, P = 0.041; I(2) = 0.0%, Pheterogeneity = 0.629). In three studies reporting DFS, no difference was observed (HR 1.00, 95% CI 0.49-2.04, P = 0.939; I(2) = 68.0%, Pheterogeneity = 0.044).

CONCLUSION

Temporary ovarian suppression with LHRHa in young breast cancer patients is associated with a reduced risk of chemotherapy-induced POF and seems to increase the pregnancy rate, without an apparent negative consequence on prognosis.

Challenges and Potential for Ovarian Preservation with SERMs

Tamoxifen (TAM) is a selective estrogen receptor modulator with tissue-specific effects on estrogen signaling used predominantly for treatment and chemoprevention of breast cancers. Recent studies have shown that TAM prevents infertility and decreases follicular loss from common cancer chemotherapy and radiation therapy in preclinical models. Here we review current and novel uses of selective estrogen receptor modulator s and advantages and challenges for translation of TAM for human fertility preservation.

Ovarian function preservation with GnRH agonist in young breast cancer patients: does it impede the effect of adjuvant chemotherapy?

BACKGROUND

Concurrent endocrine therapy with chemotherapy had a concern of potential antagonism. However, gonadotropin-releasing hormone (GnRH) agonist has been used concurrently with chemotherapy to prevent premature ovarian failure for young breast cancer patients. The aim of this study was to determine the impact of concurrent use of GnRH agonists on relapse-free and overall survival, and to establish the oncologic safety of ovarian protection with GnRH agonists.

METHODS

Premenopausal women aged between 20 and 40 years who received adjuvant chemotherapy for breast cancer from January 2002 to April 2012 were classified into two groups; One treated with GnRH agonists for ovarian protection during chemotherapy, and the other without ovarian protection. A propensity score matching strategy was used to create matched sets of two groups with age, pathologic stage, hormone receptor, and Her2 status.

RESULTS

A total of 101 patients treated with concurrent GnRH agonist during chemotherapy were compared with 335 propensity score matched patients. Among them, 81.2% were younger than 35 years and 58.4% were hormone responsive. Survival analysis using stratified Cox regression showed that women treated with concurrent GnRH agonists had better recurrence-free survival (adjusted Hazard ratio 0.21, p = 0.009; unadjusted Hazard ratio 0.33, p = 0.034).

CONCLUSIONS

Ovarian protection using GnRH agonists can be safely considered for young women with breast cancer in terms of oncologic outcomes. Further studies are needed to assess the long-term outcomes of concurrent GnRH agonist use with chemotherapy.

Combination treatment with fulvestrant and various cytotoxic agents (doxorubicin, paclitaxel, docetaxel, vinorelbine, and 5-fluorouracil) has a synergistic effect in estrogen receptor-positive breast cancer

Patients with estrogen receptor (ER)-positive breast cancers have a better prognosis than those with ER-negative breast cancers, but often have low sensitivity to chemotherapy and a limited survival benefit. We have previously shown a combination effect of taxanes and fulvestrant and suggested that this treatment may be useful for ER-positive breast cancer. In this study, we evaluated the effects of combinations of hormone drugs and chemotherapeutic agents. In vitro, the effects of combinations of five chemotherapeutic agents (doxorubicin, paclitaxel, docetaxel, vinorelbine, and 5-fluorouracil) and three hormone drugs (fulvestrant, tamoxifen, and 4-hydroxytamoxifen) were examined in ER-positive breast cancer cell lines using CalcuSyn software. Changes in chemoresistant factors such as Bcl2, multidrug resistance-associated protein 1, and microtubule-associated protein tau were also examined after exposure of the cells to hormone drugs. In vivo, tumor sizes in mice were evaluated after treatment with docetaxel or doxorubicin alone, fulvestrant alone, and combinations of these agents. Combination treatment with fulvestrant and all five chemotherapeutic agents in vitro showed synergistic effects. In contrast, tamoxifen showed an antagonistic effect with all the chemotherapeutic agents. 4-Hydroxytamoxifen showed an antagonistic effect with doxorubicin and 5-fluorouracil, but a synergistic effect with taxanes and vinorelbine. Regarding chemoresistant factors, Bcl2 and microtubule-associated protein tau were downregulated by fulvestrant. In vivo, a combination of fulvestrant and docetaxel had a synergistic effect on tumor growth, but fulvestrant and doxorubicin did not show this effect. In conclusion, fulvestrant showed good compatibility with all the evaluated chemotherapeutic agents, and especially with docetaxel, in vitro and in vivo.

The estrogen receptor influences microtubule-associated protein tau (MAPT) expression and the selective estrogen receptor inhibitor fulvestrant downregulates MAPT and increases the sensitivity to taxane in breast cancer cells

Introduction

Microtubule-associated protein tau (MAPT) inhibits the function of taxanes and high expression of MAPT decreases the sensitivity to taxanes. The relationship between estrogen receptor (ER) and MAPT in breast cancer is unclear. In this study, we examined the correlation of MAPT expression with the sensitivity of human breast cancer cells to taxanes, and the relationship between ER and MAPT.

Methods

The correlation between MAPT expression and sensitivity to taxanes was investigated in 12 human breast cancer cell lines. Alterations in cellular sensitivity to taxanes were evaluated after knockdown of MAPT expression. ER expression was knocked down or stimulated in MAPT- and ER-positive cell lines to examine the relationship between ER and MAPT. The cells were also treated with hormone drugs (tamoxifen and fulvestrant) and taxanes.

Results

mRNA expression of MAPT did not correlate with sensitivity to taxanes. However, expression of MAPT protein isoforms of less than 70 kDa was correlated with a low sensitivity to taxanes. Downregulation of MAPT increased cellular sensitivity to taxanes. MAPT protein expression was increased by stimulation with 17-β-estradiol or tamoxifen, but decreased by ER downregulation and by fulvestrant, an ER inhibitor. The combination of fulvestrant with taxanes had a synergistic effect, whereas tamoxifen and taxanes had an antagonistic effect.

Conclusions

Expression of MAPT protein isoforms of less than 70 kDa is correlated with a low sensitivity to taxanes in breast cancer cells. ER influences MAPT expression and fulvestrant increases the sensitivity to taxanes in MAPT- and ER-positive breast cancer cells.

Controversies of adjuvant endocrine treatment for breast cancer and recommendations of the 2007 St Gallen conference

Endocrine treatment for breast cancer was introduced more than a century ago. The discovery of hormone receptors has allowed targeting of endocrine treatment to patients whose primary tumours express these receptors. In the adjuvant setting, different approaches are used in premenopausal or postmenopausal women. In premenopausal patients, suppression of ovarian function and the use of tamoxifen are the most important therapeutic options, even though questions on timing, duration, and combination of these compounds remain unanswered. The use of aromatase inhibitors in combination with ovarian-function suppression is currently under investigation in the premenopausal setting. In postmenopausal patients, aromatase inhibitors given after 2-3 years or 5 years of tamoxifen have shown a significant benefit over tamoxifen alone. However, questions on this treatment also remain unanswered. For example, whether all patients should receive an aromatase inhibitor or whether some subgroups of patients might be optimally treated by tamoxifen alone is yet to be established. In this paper we review the published work on adjuvant endocrine treatment in breast cancer and provide recommendations from the 2007 St Gallen International Conference on Primary Therapy of Early Breast Cancer.

Inhibition of histone deacetylase enhances the anti-proliferative action of antiestrogens on breast cancer cells and blocks tamoxifen-induced proliferation of uterine cells

Here we report a novel potential therapeutic strategy using histone deacetylase (HDAC) inhibitors to enhance the action of hormonal therapy agents in estrogen receptor alpha (ER alpha)-positive breast cancer. HDAC inhibitors [trichostatin A (TSA), suberoylanilide hydroxamic acid (SAHA) and valproic acid (VPA)], inhibited proliferation of MCF-7 breast cancer cells and, in combination with tamoxifen inhibited proliferation better than with either agent alone. VPA, an anti-convulsant drug with HDAC inhibitory activity, enhanced tamoxifen action at doses within the concentration range used for anti-convulsive therapy. VPA cooperated with tamoxifen in a variety of ER alpha-positive cell lines and was also effective when combined with other antiestrogens, and with aromatase inhibition. VPA enhanced antiestrogen action by promoting cell death via apoptosis without affecting cell cycling. Some of this action may be due to VPA's ability to induce the pro-apoptotic gene Bik, which is also induced by antiestrogens. Remarkably, VPA blocked the undesirable pro-proliferative action of tamoxifen on uterine endometrial cells. Our in vitro results suggest that VPA and other HDAC inhibitors have the potential to enhance hormonal therapy for ER alpha-positive breast cancer and simultaneously reverse the adverse effects of antiestrogens in the uterus.

Additive antitumor effect of concurrent treatment of 4-hydroxy tamoxifen with 5-fluorouracil but not with doxorubicin in estrogen receptor-positive breast cancer cells

PURPOSE

The sequential addition of tamoxifen (TAM) to chemotherapy seems superior to its concurrent addition in patients with breast cancer. This study was conducted to clarify the hypothesis that there are differential interactions among TAM and chemotherapeutic agents.

METHODS

Estrogen receptor (ER)-alpha-positive or -negative breast cancer cells were treated with 4-hydroxy TAM (4OHT), 5-fluorouracil (FU) and/or doxorubicin (Dox). Changes in the expression levels of genes related to sensitivity and resistance to TAM, 5-FU or Dox were tested.

RESULTS

Concurrent treatment of 4OHT with 5-FU but not with Dox additively inhibited the growth of ER-alpha-positive cells. 5-FU did not change the expression levels of any tested genes related to either sensitivity or resistance to TAM. Although Dox did not change the expression levels of any genes related to the sensitivity to TAM, Dox significantly increased the expression levels of some genes related to TAM resistance, Eph A-2, ER-beta, Fos and vascular endothelial growth factor. 4OHT significantly decreased thymidilate synthase (TS) activity.

CONCLUSIONS

Although the antitumor effect of concurrent 4OHT and 5-FU was additive, that of concurrent 4OHT and Dox was less than additive in ER-alpha-positive cells. The increased expression of genes related to TAM resistance by Dox might be responsible for the interaction. Decreased TS activity by 4OHT might increase the antitumor activity of 5-FU. These findings may provide a preclinical rationale for concurrent use with 5-FU and TAM.

Maintenance Therapy to Suppress Micrometastasis: The New Challenge for Adjuvant Cancer Treatment

The palliative efficacy of cytotoxic drugs is routinely assessed using tumor shrinkage (response) rates shown in clinical trials. Although adjuvant drug therapy has a goal distinct from that of palliative therapy (i.e., to prolong survival by inhibiting progression of micrometastatic disease), it is widely assumed that the adjuvant efficacy of a drug will parallel its response rate ("activity") in advanced stages of the disease. Reconsideration of this assumption seems timely in view of recent developments: the realization that many predictors of short-term tumor response correlate inversely with long-term survival outcomes; the characterization of tumor progression as a discontinuous process that may include dormant phases; the understanding that micrometastasis is therapeutically suppressible by a variety of mechanisms including direct tumor cell kill, cytotoxic disruption of paracrine growth signals from normal tissues, and targeted inhibition of prometastatic pathways; the recognition that tumor dormancy not only blocks the antimetastatic efficacy of cytotoxic drugs but also represents a therapeutic end point for metastasis-suppressive noncytotoxic drugs such as hormone inhibitors; and the insight that optimal adjuvant drug therapy is likely to include both induction and maintenance components. The traditional view of cytoreductive response as a prerequisite for adjuvant drug efficacy thus merits reappraisal, with a view to accelerating incorporation of novel noncytotoxic maintenance therapies into controlled studies.

Paclitaxel after doxorubicin plus cyclophosphamide as adjuvant chemotherapy for node-positive breast cancer: results from NSABP B-28

PURPOSE

The primary aim of National Surgical Adjuvant Breast and Bowel Project (NSABP) B-28 was to determine whether four cycles of adjuvant paclitaxel (PTX) after four cycles of adjuvant doxorubicin/cyclophosphamide (AC) will prolong disease-free survival (DFS) and overall survival (OS) compared with four cycles of AC alone in patients with resected operable breast cancer and histologically positive axillary nodes.

PATIENTS AND METHODS

Between August 1995 and May 1998, 3,060 patients were randomly assigned (AC, 1,529; AC followed by PTX [AC --> PTX], 1,531). Patients > or = 50 years and those younger than 50 years with estrogen receptor (ER) or progesterone receptor (PR) -positive tumors also received tamoxifen for 5 years, starting with the first dose of AC. Postlumpectomy radiotherapy was mandated. Postmastectomy or regional radiotherapy was prohibited. Median follow-up is 64.6 months.

RESULTS

The addition of PTX to AC significantly reduced the hazard for DFS event by 17% (relative risk [RR], 0.83; 95% CI, 0.72 to 0.95; P = .006). Five-year DFS was 76% +/- 2% for patients randomly assigned to AC --> PTX compared with 72% +/- 2% for those randomly assigned to AC. Improvement in OS was small and not statistically significant (RR, 0.93; 95% CI, 0.78 to 1.12; P = .46). Five-year OS was 85% +/- 2% for both groups. Subset analysis of the effect of paclitaxel according to hormone receptors or tamoxifen administration did not reveal statistically significant interaction (for DFS, P = .30 and P = .44, respectively). Toxicity with the AC --> PTX regimen was acceptable for the adjuvant setting.

CONCLUSION

The addition of PTX to AC resulted in significant improvement in DFS but no significant improvement in OS with acceptable toxicity. No significant interaction between treatment effect and receptor status or tamoxifen administration was observed.

Epirubicin-cyclophosphamide adjuvant chemotherapy plus tamoxifen administered concurrently versus sequentially: randomized phase III trial in postmenopausal node-positive breast cancer patients. A GEICAM 9401 study

BACKGROUND

A prospective randomized clinical trial was implemented to assess whether the concomitant or the sequential addition of tamoxifen to chemotherapy provides improved clinical benefit in the adjuvant treatment of breast cancer in postmenopausal patients.

PATIENTS AND METHODS

Four-hundred and eighty-five patients with node-positive operable disease were randomized to receive tamoxifen (20 mg/day) concomitantly (CON) or sequentially (SEQ) to EC chemotherapy (epirubicin 75 mg/m(2) + cyclophosphamide 600 mg/m(2) on day 1, every 21 days for four cycles).

RESULTS

In the 474 fully evaluable patients there were 96 events; eight being second neoplasms and 88 being related to the breast cancer. Of these, 48 of 88 occurred in the CON arm and 40 of 88 in the SEQ arm. The Kaplan-Meier estimation of disease-free survival (DFS) at 5 years was 70% in the CON and 75% in the SEQ group (log-rank test, P = 0.43). Adjusted hazard ratio for treatment was 1.11 (95% confidence interval 0.71-1.73; P = 0.64).

CONCLUSION

This study fails to show an advantage of one treatment arm over the other, but a trend, albeit non-significant, appears to favor the sequential addition of tamoxifen to epirubicin + cyclophosphamide and, as such, warrants further investigation.

Sensitization to doxorubicin resistance in breast cancer cell lines by tamoxifen and megestrol acetate

Acquired drug resistance is a major factor in the failure of doxorubicin-based chemotherapy in breast cancer. We determined the ability of megestrol acetate and/or tamoxifen to reverse doxorubicin drug resistance in a doxorubicin-resistant breast cancer line (the human MCF-7/ADR). The cytotoxicity of doxorubicin, megestrol acetate, and/or tamoxifen was determined in the sensitive and resistant cell lines utilizing the sulphorhodamine B assay. Tamoxifen alone produced an IC50 (concentration resulting in 50% inhibition of control growth) of 10.6 microM, whereas megestrol acetate alone resulted in an IC50 of 48.7 microM in the MCF-7/ADR cell line. The IC50 of doxorubicin in MCF-7/ADR was 1.9 microM. Neither megestrol acetate alone nor tamoxifen alone at 1 or 5 microM altered the IC50 of doxorubicin. However, the combination of tamoxifen (1 or 5 microM) and megestrol acetate (1 or 5 microM) synergistically sensitized MCF-7/ADR cells. Additionally, megestrol acetate and tamoxifen inhibited iodoarylazidoprazosin binding to P-glycoprotein, and, in their presence, there was an increased doxorubicin accumulation in the MCF-7/ADR cells. Furthermore, the combination of tamoxifen and megestrol acetate had much less effect on the cytotoxicity of doxorubicin in MCF-7 wild-type cells. Clinically achievable concentrations of tamoxifen and megestrol acetate can largely sensitize MCF-7/ADR to doxorubicin. The combination of these three drugs in a clinical trial may be informative.