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Importance: Immune checkpoint inhibitors (ICIs) have limited activity in microsatellite-stable (MSS) or mismatch repair-proficient (pMMR) colorectal cancer. Recent findings suggest the efficacy of ICIs may be modulated by the presence of liver metastases (LM). Objective: To investigate the association between the presence of LM and ICI activity in advanced MSS colorectal cancer. Design, Setting, and Participants: In this secondary analysis of the Canadian Cancer Trials Group CO26 (CCTG CO.26) randomized clinical trial, patients with treatment-refractory colorectal cancer were randomized in a 2:1 fashion to durvalumab plus tremelimumab or best supportive care alone between August 10, 2016, and June 15, 2017. The primary end point was overall survival (OS) with 80% power and 2-sided α = .10. The median follow-up was 15.2 (0.2-22.0) months. In this post hoc analysis performed from February 11 to 14, 2022, subgroups were defined based on the presence or absence of LM and study treatments. Intervention: Durvalumab plus tremelimumab or best supportive care. Main Outcomes and Measures: Hazard ratios (HRs) and 90% CIs were calculated based on a stratified Cox proportional hazards regression model. Plasma tumor mutation burden at study entry was determined using a circulating tumor DNA assay. The primary end point of the study was OS, defined as the time from randomization to death due to any cause; secondary end points included progression-free survival (PFS) and disease control rate (DCR). Results: Of 180 patients enrolled (median age, 65 [IQR, 36-87] years; 121 [67.2%] men; 19 [10.6%] Asian, 151 [83.9%] White, and 10 [5.6%] other race or ethnicity), LM were present in 127 (70.6%). For patients with LM, there was a higher proportion of male patients (94 of 127 [74.0%] vs 27 of 53 [50.9%]; P = .005), and the time from initial cancer diagnosis to study entry was shorter (median, 40 [range, 8-153] vs 56 [range, 14-181] months; P = .001). Plasma tumor mutation burden was significantly higher in patients with LM. Patients without LM had significantly improved PFS with durvalumab plus tremelimumab (HR, 0.54 [90% CI, 0.35-0.96]; P = .08; P = .02 for interaction). Disease control rate was 49% (90% CI, 36%-62%) in patients without LM treated with durvalumab plus tremelimumab, compared with 14% (90% CI, 6%-38%) in those with LM (odds ratio, 5.70 [90% CI, 1.46-22.25]; P = .03). On multivariable analysis, patients without LM had significantly improved OS and PFS compared with patients with LM. Conclusions and Relevance: In this secondary analysis of the CCTG CO.26 study, the presence of LM was associated with worse outcomes for patients with advanced colorectal cancer. Patients without LM had improved PFS and higher DCR with durvalumab plus tremelimumab. Liver metastases may be associated with poor outcomes of ICI treatment in advanced colorectal cancer and should be considered in the design and interpretation of future clinical studies evaluating this therapy.
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Neoplasias do Colo , Neoplasias Colorretais , Neoplasias Hepáticas , Neoplasias Retais , Idoso , Feminino , Humanos , Masculino , Biomarcadores Tumorais/análise , Canadá , Neoplasias do Colo/tratamento farmacológico , Neoplasias Colorretais/tratamento farmacológico , Inibidores de Checkpoint Imunológico/uso terapêutico , Neoplasias Hepáticas/tratamento farmacológico , Intervalo Livre de Progressão , Neoplasias Retais/tratamento farmacológico , Adulto , Pessoa de Meia-Idade , Idoso de 80 Anos ou maisRESUMO
BACKGROUND: For many patients with resected epidermal growth factor receptor mutation-positive (EGFRm) non-small cell lung cancer (NSCLC), current standard of care (SoC) is adjuvant chemotherapy; however, disease recurrence remains high. Based on positive results from ADAURA (NCT02511106), adjuvant osimertinib was approved for treatment of resected stage IBâIIIA EGFRm NSCLC. OBJECTIVE: The aim was to assess the cost-effectiveness of adjuvant osimertinib in patients with resected EGFRm NSCLC. METHODS: A five-health-state, state-transition model with time dependency was developed to estimate lifetime (38 years) costs and survival of resected EGFRm patients treated with adjuvant osimertinib or placebo (active surveillance), with/without prior adjuvant chemotherapy, using a Canadian Public Healthcare perspective. Transitions between health states were modeled using ADAURA and FLAURA (NCT02296125) data, Canadian life tables, and real-world data (CancerLinQ Discovery®). The model used a 'cure' assumption: patients remaining disease free for 5 years after treatment completion for resectable disease were deemed 'cured.' Health state utility values and healthcare resource usage estimates were derived from Canadian real-world evidence. RESULTS: In the reference case, adjuvant osimertinib treatment led to a mean 3.20 additional quality-adjusted life-years (QALYs; (11.77 vs 8.57) per patient, versus active surveillance. The modeled median percentage of patients alive at 10 years was 62.5% versus 39.3%, respectively. Osimertinib was associated with mean added costs of Canadian dollars (C$)114,513 per patient and a cost/QALY (incremental cost-effectiveness ratio) of C$35,811 versus active surveillance. Model robustness was demonstrated by scenario analyses. CONCLUSIONS: In this cost-effectiveness assessment, adjuvant osimertinib was cost-effective compared with active surveillance for patients with completely resected stage IBâIIIA EGFRm NSCLC after SoC.
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BACKGROUND: Therapeutic resistance is the main cause of death in metastatic colorectal cancer. To investigate genomic plasticity, most specifically of metastatic lesions, associated with response to first-line systemic therapy, we collected longitudinal liver metastatic samples and characterized the copy number aberration (CNA) landscape and its effect on the transcriptome. METHODS: Liver metastatic biopsies were collected prior to treatment (pre, n = 97) and when clinical imaging demonstrated therapeutic resistance (post, n = 43). CNAs were inferred from whole exome sequencing and were correlated with both the status of the lesion and overall patient progression-free survival (PFS). We used RNA sequencing data from the same sample set to validate aberrations as well as independent datasets to prioritize candidate genes. RESULTS: We identified a significantly increased frequency gain of a unique CN, in liver metastatic lesions after first-line treatment, on chr18p11.32 harboring 10 genes, including TYMS, which has not been reported in primary tumors (GISTIC method and test of equal proportions, FDR-adjusted p = 0.0023). CNA lesion profiles exhibiting different treatment responses were compared and we detected focal genomic divergences in post-treatment resistant lesions but not in responder lesions (two-tailed Fisher's Exact test, unadjusted p ≤ 0.005). The importance of examining metastatic lesions is highlighted by the fact that 15 out of 18 independently validated CNA regions found to be associated with PFS in this study were only identified in the metastatic lesions and not in the primary tumors. CONCLUSION: This investigation of genomic-phenotype associations in a large colorectal cancer liver metastases cohort identified novel molecular features associated with treatment response, supporting the clinical importance of collecting metastatic samples in a defined clinical setting.
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Neoplasias Colorretais/genética , Variações do Número de Cópias de DNA/genética , Transcriptoma/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Antineoplásicos/uso terapêutico , Bevacizumab/uso terapêutico , Neoplasias Colorretais/tratamento farmacológico , Neoplasias Colorretais/patologia , Resistencia a Medicamentos Antineoplásicos/genética , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Neoplasias Hepáticas/secundário , Masculino , Pessoa de Meia-Idade , Intervalo Livre de Progressão , Sequenciamento do ExomaRESUMO
Importance: Single-agent immune checkpoint inhibition has not shown activities in advanced refractory colorectal cancer (CRC), other than in those patients who are microsatellite-instability high (MSI-H). Objective: To evaluate whether combining programmed death-ligand 1 (PD-L1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibition improved patient survival in metastatic refractory CRC. Design, Setting, and Participants: A randomized phase 2 study was conducted in 27 cancer centers across Canada between August 2016 and June 2017, and data were analyzed on October 18, 2018. Eligible patients had histologically confirmed adenocarcinoma of the colon or rectum; received all available standard systemic therapies (fluoropyrimidines, oxaliplatin, irinotecan, and bevacizumab if appropriate; cetuximab or panitumumab if RAS wild-type tumors; regorafenib if available); were aged 18 years or older; had adequate organ function; had Eastern Cooperative Oncology Group performance status of 0 or 1, and measurable disease. Interventions: We randomly assigned patients to receive either 75 mg of tremelimumab every 28 days for the first 4 cycles plus 1500 mg durvalumab every 28 days, or best supportive care alone (BSC) in a 2:1 ratio. Main Outcomes and Measures: The primary end point was overall survival (OS) and a 2-sided P<.10 was considered statistically significant. Circulating cell-free DNA from baseline plasma was used to determine microsatellite instability (MSI) and tumor mutation burden (TMB). Results: Of 180 patients enrolled (121 men [67.2%] and 59 women [32.8%]; median [range] age, 65 [36-87] years), 179 were treated. With a median follow-up of 15.2 months, the median OS was 6.6 months for durvalumab and tremelimumab and 4.1 months for BSC (hazard ratio [HR], 0.72; 90% CI, 0.54-0.97; P = .07). Progression-free survival was 1.8 months and 1.9 months respectively (HR, 1.01; 90% CI, 0.76-1.34). Grade 3 or 4 adverse events were significantly more frequent with immunotherapy (75 [64%] patients in the treatment group had at least 1 grade 3 or higher adverse event vs 12 [20%] in the BSC group). Circulating cell-free DNA analysis was successful in 168 of 169 patients with available samples. In patients who were microsatellite stable (MSS), OS was significantly improved with durvalumab and tremelimumab (HR, 0.66; 90% CI, 0.49-0.89; P = .02). Patients who were MSS with plasma TMB of 28 variants per megabase or more (21% of MSS patients) had the greatest OS benefit (HR, 0.34; 90% CI, 0.18-0.63; P = .004). Conclusions and Relevance: This phase 2 study suggests that combined immune checkpoint inhibition with durvalumab plus tremelimumab may be associated with prolonged OS in patients with advanced refractory CRC. Elevated plasma TMB may select patients most likely to benefit from durvalumab and tremelimumab. Further confirmation studies are warranted. Trial Registration: ClinicalTrials.gov Identifier: NCT02870920.
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Anticorpos Monoclonais Humanizados/uso terapêutico , Anticorpos Monoclonais/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Antígeno B7-H1/antagonistas & inibidores , Neoplasias Colorretais/terapia , Inibidores de Checkpoint Imunológico/uso terapêutico , Cuidados Paliativos , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticorpos Monoclonais/efeitos adversos , Anticorpos Monoclonais Humanizados/efeitos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Canadá , Neoplasias Colorretais/mortalidade , Feminino , Humanos , Inibidores de Checkpoint Imunológico/efeitos adversos , Imunoterapia/efeitos adversos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Intervalo Livre de ProgressãoRESUMO
BACKGROUND: The combination of an anti-VEGF or an anti-EGFR-targeted monoclonal antibody with chemotherapy has shown clinical activity in patients with metastatic colorectal cancer. However, combining both anti-VEGF and anti-EGFR antibodies with chemotherapy in first-line treatment resulted in adverse outcomes. We assessed whether the combination of erlotinib, an EGFR tyrosine kinase inhibitor, with bevacizumab could increase the efficacy of maintenance therapy in patients with unresectable metastatic colorectal cancer. METHODS: This randomised, open-label, phase 3 study was undertaken in 49 centres in France, Austria, and Canada. Eligible patients were aged 18-80 years with histologically confirmed, unresectable metastatic colorectal cancer, WHO performance status 0-2, had received no previous therapy for metastatic disease, and had adequate organ function. Patients without disease progression after bevacizumab-based induction therapy were randomly assigned (1:1) by a minimisation technique to bevacizumab (7·5 mg/kg every 3 weeks) or bevacizumab plus erlotinib (150 mg once daily) as maintenance therapy until progression. All patients were stratified by centre, baseline performance status, age, and number of metastatic sites. The primary endpoint was progression-free survival on maintenance therapy analysed by intention to treat. We report the final analysis. This trial is registered with ClinicalTrials.gov, number NCT00265824. FINDINGS: Between Jan 1, 2007, and Oct 13, 2011, 700 eligible patients were enrolled; following induction treatment, patients without disease progression were randomly assigned to bevacizumab (n=228) or bevacizumab plus erlotinib (n=224). At the final analysis, median follow-up was 51·0 months (IQR 36·0-60·0) in the bevacizumab group and 48·3 months (31·5-61·0) in the bevacizumab plus erlotinib group. In the primary analysis (after 231 progression-free survival events), median progression-free survival from randomisation was 5·1 months (95% CI 4·1-5·9) in the bevacizumab plus erlotinib group compared with 6·0 months (4·6-7·9) in the bevacizumab group (stratified hazard ratio [HR] 0·79 [95% CI 0·60-1·06]; p=0·11; unstratified HR 0·76 [0·59-0·99]; p=0·043). In the final analysis, median progression-free survival from randomisation was 5·4 months (95% CI 4·3-6·2) in the bevacizumab plus erlotinib group compared with 4·9 months (4·1-5·7) in the bevacizumab group (stratified HR 0·81 [95% CI 0·66-1·01], p=0·059; unstratified HR 0·78 [0·68-0·96], p=0·019). At the final analysis, median overall survival from maintenance was 24·9 months (95% CI 21·4-28·9) in the bevacizumab plus erlotinib group and 22·1 months (19·6-26·7) in the bevacizumab group (stratified HR 0·79 [95% CI 0·63-0·99], p=0·036; unstratified HR 0·79 [0·64-0·98], p=0·035). The most frequent grade 3-4 adverse events were skin rash (47 [21%] of 220 patients in the bevacizumab plus erlotinib group vs none of 224 patients in the bevacizumab alone group), diarrhoea (21 [10%] vs two [<1%]), and asthenia (12 [5%] vs two [<1%]). INTERPRETATION: Maintenance bevacizumab plus erlotinib might be a new non-chemotherapy-based maintenance option for the first-line treatment of patients with unresectable metastatic colorectal cancer after bevacizumab-based induction therapy. FUNDING: GERCOR and F Hoffmann-La Roche.
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Inibidores da Angiogênese/administração & dosagem , Antineoplásicos/administração & dosagem , Bevacizumab/administração & dosagem , Neoplasias Colorretais/tratamento farmacológico , Neoplasias Colorretais/secundário , Cloridrato de Erlotinib/administração & dosagem , Quimioterapia de Manutenção , Idoso , Intervalo Livre de Doença , Quimioterapia Combinada , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Lung cancer is the second most diagnosed cancer and the leading cause of cancer-related mortality in Canada. Surgical resection is the treatment of choice for patients with stage I non-small-cell lung cancer (NSCLC). However, 20% to 30% of them are deemed medically inoperable and may be offered radiation therapy. Standard external-beam radiation therapy (EBRT) is associated with high rates of local recurrence and poor long-term survival. Stereotactic ablative radiation therapy (SABR) is increasingly being proposed for inoperable patients, and the use of this treatment modality for operable patients is also being contemplated. The objective of this guideline is to review the efficacy and safety of SABR in these two clinical situations and to develop evidence-based recommendations. METHOD: A review of the scientific literature published up to December 2013 was performed. A total of 44 publications were included. RECOMMENDATIONS: Considering the evidence available to date, the Comité de l'évolution des pratiques en oncologie recommends the following: (1) for medically operable patients with stage T1-2N0M0 NSCLC, surgery remains the standard treatment because comparative data regarding the efficacy of SABR and surgery are currently insufficient for SABR to be considered an equivalent alternative to surgery for these patients; (2) for medically inoperable patients with stage T1-2N0M0 NSCLC or medically operable patients who refuse surgery, SABR should be preferred to standard EBRT (grade B recommendation); (3) the biological equivalent dose (BED(10)) used for SABR treatment should be at least 100 Gy (grade B recommendation); (4) for patients with a central tumor, a large-volume tumor (large planning target volume) or severe pulmonary comorbidity, a risk-adaptive schedule should be used (dose reduction or increase in the number of fractions; grade B recommendation); (5) the choice of using SABR to treat NSCLC should be discussed within tumor boards; treatment with SABR (or with standard EBRT) should not be considered for patients whose life expectancy is very limited because of comorbidities (grade D recommendation).
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Carcinoma Pulmonar de Células não Pequenas/cirurgia , Neoplasias Pulmonares/cirurgia , Radiocirurgia/métodos , Carcinoma Pulmonar de Células não Pequenas/patologia , Humanos , Neoplasias Pulmonares/patologia , Dosagem RadioterapêuticaRESUMO
BACKGROUND: Interdisciplinary teamwork (ITW) is designed to promote the active participation of several disciplines in delivering comprehensive cancer care to patients. ITW provides mechanisms to support continuous communication among care providers, optimize professionals' participation in clinical decision-making within and across disciplines, and foster care coordination along the cancer trajectory. However, ITW mechanisms are not activated optimally by all teams, resulting in a gap between desired outcomes of ITW and actual outcomes observed. The aim of the present study is to identify the conditions underlying outcome production by ITW in local oncology teams. METHODS: This retrospective multiple case study will draw upon realist evaluation principles to explore associations among context, mechanisms and outcomes (CMO). The cases are nine interdisciplinary cancer teams that participated in a previous study evaluating ITW outcomes. Qualitative data sources will be used to construct a picture of CMO associations in each case. For data collection, reflexive focus groups will be held to capture patients' and professionals' perspectives on ITW, using the guiding question, 'What works, for whom, and under what circumstances?' Intra-case analysis will be used to trace associations between context, ITW mechanisms, and patient outcomes. Inter-case analysis will be used to compare the different cases' CMO associations for a better understanding of the phenomenon under study. DISCUSSION: This multiple case study will use realist evaluation principles to draw lessons about how certain contexts are more or less likely to produce particular outcomes. The results will make it possible to target more specifically the actions required to optimize structures and to activate the best mechanisms to meet the needs of cancer patients. This project could also contribute significantly to the development of improved research methods for conducting realist evaluations of complex healthcare interventions. To our knowledge, this study is the first to use CMO associations to improved empirical and theoretical understanding of interdisciplinary teamwork in oncology, and its results could foster more effective implementation in clinical practice.
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Comunicação , Tomada de Decisões , Neoplasias/terapia , Avaliação de Processos e Resultados em Cuidados de Saúde/organização & administração , Equipe de Assistência ao Paciente/organização & administração , Protocolos Clínicos , Medicina Baseada em Evidências , Humanos , Relações Interprofissionais , Quebeque , Projetos de Pesquisa , Estudos RetrospectivosRESUMO
OBJECTIVE: Despite the very good prognosis of endometrial cancer, a number of patients with localized disease relapse following surgery. Therefore, various adjuvant therapeutic approaches have been studied. The objective of this review is to evaluate the efficacy and safety of neoadjuvant and adjuvant therapies in patients with resectable endometrial cancer and to develop evidence-based recommendations. METHODS: A review of the scientific literature published between January 1990 and June 2012 was performed. The search was limited to published phase III clinical trials and meta-analyses evaluating the efficacy of neoadjuvant or adjuvant therapies in patients with endometrial carcinoma or carcinosarcoma. A total of 23 studies and five meta-analyses were identified. RESULTS: The selected literature showed that in patients with a low risk of recurrence, post-surgical observation is safe and recommended in most cases. There are several therapeutic modalities available for treatment of endometrial cancers with higher risk of recurrence, including vaginal brachytherapy, external beam radiotherapy, chemotherapy, or a combination of these. CONCLUSIONS: Considering the evidence available to date, the CEPO recommends the following: (1)post-surgical observation for most patients with a low recurrence risk; (2)adjuvant vaginal brachytherapy for patients with an intermediate recurrence risk; (3)adjuvant pelvic radiotherapy with or without vaginal brachytherapy for patients with a high recurrence risk; addition of adjuvant chemotherapy may be considered as an option for selected patients (excellent functional status, no significant co-morbidities, poor prognostic factors); (4)adjuvant chemotherapy and pelvic radiotherapy with or without brachytherapy and para-aortic irradiation for patients with advanced disease;
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Adenocarcinoma/terapia , Carcinossarcoma/terapia , Terapia Combinada , Neoplasias do Endométrio/terapia , Recidiva Local de Neoplasia/prevenção & controle , Adenocarcinoma/patologia , Adenocarcinoma/cirurgia , Braquiterapia , Carcinossarcoma/cirurgia , Quimioterapia Adjuvante , Neoplasias do Endométrio/patologia , Neoplasias do Endométrio/cirurgia , Feminino , Hormônios/uso terapêutico , Humanos , Radioterapia AdjuvanteRESUMO
Great advances in analytical technology coupled with accelerated new drug development and growing understanding of biological challenges, such as tumor heterogeneity, have required a change in the focus for biobanking. Most current banks contain samples of primary tumors, but linking molecular signatures to therapeutic questions requires serial biopsies in the setting of metastatic disease, next-generation of biobanking. Furthermore, an integration of multidimensional analysis of various molecular components, that is, RNA, DNA, methylome, microRNAome and post-translational modifications of the proteome, is necessary for a comprehensive view of a tumor's biology. While data using such biopsies are now regularly presented, the preanalytical variables in tissue procurement and processing in multicenter studies are seldom detailed and therefore are difficult to duplicate or standardize across sites and across studies. In the context of a biopsy-driven clinical trial, we generated a detailed protocol that includes morphological evaluation and isolation of high-quality nucleic acids from small needle core biopsies obtained from liver metastases. The protocol supports stable shipping of samples to a central laboratory, where biopsies are subsequently embedded in support media. Designated pathologists must evaluate all biopsies for tumor content and macrodissection can be performed if necessary to meet our criteria of >60% neoplastic cells and <20% necrosis for genomic isolation. We validated our protocol in 40 patients who participated in a biopsy-driven study of therapeutic resistance in metastatic colorectal cancer. To ensure that our protocol was compatible with multiplex discovery platforms and that no component of the processing interfered with downstream enzymatic reactions, we performed array comparative genomic hybridization, methylation profiling, microRNA profiling, splicing variant analysis and gene expression profiling using genomic material isolated from liver biopsy cores. Our standard operating procedures for next-generation biobanking can be applied widely in multiple settings, including multicentered and international biopsy-driven trials.
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Biomarcadores Tumorais/genética , Neoplasias Colorretais/genética , Neoplasias Colorretais/patologia , Testes Genéticos , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/secundário , Medicina de Precisão , Bancos de Tecidos , Processamento Alternativo , Biópsia com Agulha de Grande Calibre , Canadá , Hibridização Genômica Comparativa , Metilação de DNA , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Predisposição Genética para Doença , Testes Genéticos/métodos , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , MicroRNAs/análise , Análise de Sequência com Séries de Oligonucleotídeos , Seleção de Pacientes , Fenótipo , Medicina de Precisão/métodos , Valor Preditivo dos Testes , Prognóstico , Reprodutibilidade dos Testes , Manejo de Espécimes , Fluxo de TrabalhoRESUMO
PURPOSE: To determine the efficacy and safety of EM-800 (SCH-57050), the precursor of acolbifene, a new, highly potent, orally active, pure antiestrogen in the mammary gland and endometrium, for the treatment of tamoxifen-resistant breast cancer. PATIENTS AND METHODS: Forty-three post menopausal/ovariectomized women with breast cancer who had received tamoxifen, either for metastatic disease or as adjuvant to surgery for > or = 1 year, and had relapsed were treated in a prospective, multicenter, phase II study with EM-800 (20 mg/d [n = 21] or 40 mg/d [n = 22] orally). Results Thirty-seven patients had estrogen receptor (ER)-positive tumors (>10 fmol/mg; mean, 146 fmol/mg cytosolic protein), three patients had ER-negative/progesterone receptor-positive tumors, and three patients had undetermined ER status. The objective response rate to EM-800 was 12%, with one complete response and four partial responses. Ten patients (23%) had stable disease for > or = 3 months, and 7 patients (16%) had stable disease for > or = 6 months. With a median follow-up of 29 months, median duration of response was 8 months (range, 7 to 71+ months). Treatment with EM-800 was well tolerated. No significant adverse events related to the study drug were observed clinically or biochemically. CONCLUSION: EM-800 produced responses in a significant proportion of patients with tamoxifen-resistant breast cancer, thus showing that this highly potent, selective estrogen receptor modulator, which lacks estrogenic activity in the mammary gland and endometrium, has incomplete cross-resistance with tamoxifen, thus suggesting additional benefits in the treatment of breast cancer.