Examining Urban and Rural Differences in How Distance to Care Influences the Initiation and Completion of Treatment among Insured Cervical Cancer Patients.

BACKGROUND: Although rural cancer patients encounter substantial barriers to care, they more often report receiving timely care than urban patients. We examined whether geographic distance, a contributor to urban-rural health disparities, differentially influences treatment initiation and completion among insured urban and rural cervical cancer patients. METHODS: We identified women diagnosed with cervical cancer from 2004 to 2013 from a statewide cancer registry linked to multipayer, insurance claims. Primary outcomes were initiation of guideline-concordant care within 6 weeks of diagnosis and, among stage IB2-IVA cancer patients, completion of concurrent chemoradiotherapy (CCRT) in 56 days. We estimated risk ratios using modified Poisson regressions, stratified by urban/rural status, to examine the association between distance and treatment timing (initiation or completion). RESULTS: Among 999 stage IA-IVA patients, 48% initiated guideline-concordant care within 6 weeks of diagnosis, and 37% of 492 stage IB2-IVA cancer patients completed CCRT in 56 days. In urban areas, stage IA-IVA patients who lived ≥15 miles from the nearest treatment facility were less likely to initiate timely treatment compared with those <5 miles [risk ratio (RR): 0.72; 95% confidence intervals (CI), 0.54-0.95]. Among IB2-IVA stage cancer patients, rural women residing ≥15 miles from the nearest radiation facility were more likely to complete CCRT in 56 days (RR: 2.49; 95% CI, 1.12-5.51). CONCLUSIONS: Geographic distance differentially influences the initiation and completion of treatment among urban and rural cervical cancer patients. IMPACT: Distance was an access barrier for insured cervical cancer patients in urban areas whereas rural patients may require more intensive outreach, support, and resources, even among those living closer to treatment.

Effect of race and histology on patterns of failure in women with early stage endometrial cancer treated with high dose rate brachytherapy.

BACKGROUND: Clinical trials have helped refine management of early stage endometrial cancer (EC). For patients with intermediate risk features, adjuvant radiation is considered, primarily vaginal cuff brachytherapy. For higher risk patients, there may be a role for chemotherapy and radiation. The purpose of this study is to examine patterns of failure for early stage EC patients treated with postoperative high dose rate brachytherapy. METHODS: In this single institution retrospective cohort study, 208 women with early stage endometrial cancer who received definitive therapy between January 1, 2000 and January 1, 2013 were identified. RESULTS: Median follow-up was 46.4 (range, 6.2-137.3) months. Thirteen (6.3%) patients developed with locoregional recurrent disease and 15 (7.2%) patients developed distant metastasis. Freedom from recurrence at 5 years was 88.6% for white patients and 60.5% for black patients (p=0.0093). Five year recurrence free survival (RFS) for white vs. black patients was 82.9% vs. 48.9% (p=0.0007). Five year overall survival (OS) was 86.8% for white patients and 59.5% for black patients (p=0.0023). Black patients with unfavorable histology treated with chemotherapy and vaginal brachytherapy had a 15% locoregional recurrence rate, more than double the rate of local recurrence compared to AA patients with endometrioid histology and white patients with any histology (6% locoregional recurrence rate). CONCLUSIONS: Black women with unfavorable histology early stage EC experience increased rates of recurrence and worse survival compared to white patients. Patterns of failure in this group also indicate a high locoregional failure rate for the black patients with unfavorable histology (type II).

ACR appropriateness Criteria® advanced stage endometrial cancer.

OBJECTIVES: Patients with advanced stage endometrial carcinoma constitute a heterogeneous group of patients with different stages, tumor histologic types, and involved sites. Hysterectomy, bilateral salpingo-ophorectomy, and surgical staging are the cornerstone of surgical management in these patients. The optimal adjuvant therapy is yet to be established. An expert panel was convened to reach consensus on the most appropriate management options in this group of patients. METHODS: The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment. RESULTS: Four clinical variants were developed to address common scenarios in the management of women with advanced-stage endometrial carcinoma. Group members reached consensus on the appropriateness of specific evaluation and treatment approaches with numerical ratings. CONCLUSIONS: In combining available medical literature and expert opinions, this manuscript may serve as an aid for other practitioners in the appropriate management of women with advanced-stage endometrial carcinoma.

ACR Appropriateness Criteria® management of locoregionally advanced squamous cell carcinoma of the vulva.

OBJECTIVES: Locoregionally advanced vulvar cancer (LRAVC) is a rare disease that presents many challenging medical decisions. An expert panel was convened to reach consensus on the most appropriate pretreatment assessment and therapeutic interventions in LRAVC patients. METHODS: The American College of Radiology Appropriateness Criteria are evidenced-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journal and the application of a well-established consensus methodology (modified Delphi) to rate appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to formulate recommendations. RESULTS: Three clinical variants were developed to address common scenarios in the management of LRAVC. Group members reached consensus on the appropriateness of specific evaluation and treatment approaches, with numerical ratings and descriptive commentary. CONCLUSIONS: In combining available medical literature and expert opinion, this manuscript may serve as an aid for other practitioners in the appropriate management of patients with LRAVC.

Hypoxia regulation of phosphokinases and the prognostic value of pAKT in breast cancer.

Tumor hypoxia results in poor treatment response and is an indicator of poor outcome in cancer patients. TRIB3 is a hypoxia-upregulated protein involved in the ability of breast cancer cells to survive in hypoxic conditions. It is also involved in the prognosis of cancer patients, possibly by affecting several kinase-signaling pathways. We set out to establish which kinase-signaling pathways are regulated by hypoxia and whether these kinases are relevant for breast cancer prognosis. Using a phosphokinase antibody array comparing cells cultured under hypoxic conditions with those cultured during normoxia, we found that the phosphorylation status of ERK1/2, AKT, p70 S6 kinase, Lck and STAT3 was altered in both MCF7 and MDA-MB-231 breast cancer cells. Using Western blotting, we found that phosphorylated AKT (pAKT) increased in hypoxic conditions. Knockdown of TRIB3 attenuated this effect of hypoxia on AKT activation. Both pAKT and TRIB3 were expressed in pimonidazole-positive, hypoxic areas of human breast cancer tumors. In breast cancer patients significantly lower 5-year disease-free survival was observed for the pAKT-positive compared to the pAKT-negative group (64.6% vs 86.1%, p=0.03). In conclusion, the phosphorylation status of AKT is increased in hypoxic conditions and TRIB3 knockdown attenuates this response. Furthermore, pAKT expression denotes a worse prognosis in breast cancer patients. The hypoxia-related activation of AKT could explain the resistance to various treatments including chemotherapy and radiotherapy.

Acr appropriateness Criteria management of vaginal cancer.

Due to its rarity, treatment guidelines for vaginal cancer are extrapolated from institutional reports and prospective studies of cervical and anal cancer. An expert panel was convened to reach consensus on the selection of imaging and therapeutic modalities. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) used by the panel to rate the appropriateness of imaging and treatment procedures. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment. Four variants were developed to represent clinical scenarios in vaginal cancer management. Group members reached consensus on the appropriateness of the pretreatment evaluation and therapeutic interventions. This article represents the consensus opinion of an expert panel and may be used to inform clinical recommendations in vaginal cancer management.

ACR Appropriateness Criteria® definitive therapy for early-stage cervical cancer.

OBJECTIVES: The definitive treatment of early-stage cervical cancer involves multidisciplinary decision making. This expert panel was convened to reach consensus on the selection of appropriate therapies based on patient and disease characteristics at presentation. METHODS: The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or the treatment. RESULTS: Three clinical variants were developed to represent common scenarios in the treatment of early-stage cervical cancer. Group members reached consensus on the appropriateness of therapeutic options. This process yielded numerical ratings and descriptive commentary. CONCLUSIONS: This manuscript represents the consensus opinion of an expert panel based on a survey of all available medical literature. This manuscript may be used to inform the clinical decision making of physicians involved in the treatment of early-stage cervical cancer.

ACR Appropriateness Criteria® pretreatment planning of invasive cancer of the cervix.

The prognosis of cervical cancer is linked to lymph node involvement, and this is predicted clinically and pathologically by the stage of the disease, as well as the volume and grade of the tumor. Staging of cervical cancer based on International Federation of Gynecology and Obstetrics (FIGO) staging uses physical examination, cystoscopy, proctoscopy, intravenous urography, and barium enema. It does not include CT or MRI. Evaluation of the parametrium is limited in FIGO staging, and lymph node metastasis, an important prognostic factor, is not included in FIGO staging. The most important role for imaging is to distinguish stages Ia, Ib, and IIa disease treated with surgery from advanced disease treated with radiation therapy with or without chemotherapy. This article reviews the current role of imaging in pretreatment planning of invasive cervical cancer. The ACR Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

ACR Appropriateness Criteria® role of adjuvant therapy in the management of early stage cervical cancer.

OBJECTIVE: The use of adjuvant treatment(s) following initial hysterectomy and retroperitoneal nodal harvesting of patients with clinical stage I and II cervical carcinoma is (are) presently based on the pathological assessment of surgical specimens. This report sought to delineate further the clinical application of potential therapeutic interventions and associated follow-up investigations of this patient cohort. METHODS: The American College of Radiology (ACR) Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every two years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journal and the application of a well-established consensus methodology (modified Delphi) to rate appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment. RESULTS: From this process, 5 unique clinical variants were developed. These scenarios pertained to options of adjuvant radiation therapy and chemotherapy, methods of delivery of radiotherapy to optimize target volume coverage while simultaneously minimizing radiation exposure of adjacent healthy organs, and recommendations for patient follow-up care. Group members reached consensus of topic ratings in descending order of importance. A risk assessment breakdown was established to highlight the most likely indications for adjuvant treatment(s). CONCLUSION: This assembly by the ACR of physicians involved in the management of patients with early stage cervical cancer was able to describe appropriateness criteria to aid other practitioners in selecting reasonable implementation of postoperative therapies and subsequent surveillance studies. These guidelines await further validation and refinement by both current and future prospectively randomized clinical studies regarding this patient population.

Endogenous myoglobin in breast cancer is hypoxia-inducible by alternative transcription and functions to impair mitochondrial activity: a role in tumor suppression?

Recently, immunohistochemical analysis of myoglobin (MB) in human breast cancer specimens has revealed a surprisingly widespread expression of MB in this nonmuscle context. The positive correlation with hypoxia-inducible factor 2α (HIF-2α) and carbonic anhydrase IX suggested that oxygen regulates myoglobin expression in breast carcinomas. Here, we report that MB mRNA and protein levels are robustly induced by prolonged hypoxia in breast cancer cell lines, in part via HIF-1/2-dependent transactivation. The hypoxia-induced MB mRNA originated from a novel alternative transcription start site 6 kb upstream of the ATG codon. MB regulation in normal and tumor tissue may thus be fundamentally different. Functionally, the knockdown of MB in MDA-MB468 breast cancer cells resulted in an unexpected increase of O(2) uptake and elevated activities of mitochondrial enzymes during hypoxia. Silencing of MB transcription attenuated proliferation rates and motility capacities of hypoxic cancer cells and, surprisingly, also fully oxygenated breast cancer cells. Endogenous MB in cancer cells is apparently involved in controlling oxidative cell energy metabolism, contrary to earlier findings on mouse heart, where the targeted disruption of the Mb gene did not effect myocardial energetics and O(2) consumption. This control function of MB seemingly impacts mitochondria and influences cell proliferation and motility, but it does so in ways not directly related to the facilitated diffusion or storage of O(2). Hypothetically, the mitochondrion-impairing role of MB in hypoxic cancer cells is part of a novel tumor-suppressive function.

Tribbles homolog 3 denotes a poor prognosis in breast cancer and is involved in hypoxia response.

INTRODUCTION: Hypoxia in solid tumors is associated with treatment resistance, resulting in poor prognosis. Tribbles homolog 3 (TRIB3) is induced during hypoxia and is involved in multiple cellular pathways involved in cell survival. Here, we investigated the role of TRIB3 in breast cancer. METHODS: TRIB3 mRNA expression was measured in breast tumor tissue from 247 patients and correlated with clinicopathological parameters and clinical outcome. Furthermore, we studied TRIB3 expression regulation in cell lines, xenografts tissues and human breast cancer material using Reverse transcriptase, quantitative polymerase chain reaction (RT-qPCR) and immunohistochemical staining. Finally, the effect of small interfering RNA (siRNA) mediated TRIB3 knockdown on hypoxia tolerance was assessed. RESULTS: Breast cancer patients with low, intermediate or high TRIB3 expression exhibited a mean disease free survival (DFS) of 80 (95% confidence interval [CI] = 74 to 86), 74 (CI = 67 to 81), and 63 (CI = 55 to 71) months respectively (P = .002, Mantel-Cox log-rank). The prognostic value of TRIB3 was limited to those patients that had received radiotherapy as part of their primary treatment (n = 179, P = .005) and remained statistically significant after correction for other clinicopathological parameters (DFS, Hazard Ratio = 1.90, CI = 1.17 to 3.08, P = .009). In breast cell lines TRIB3 expression was induced by hypoxia, nutrient starvation, and endoplasmic reticulum stress in an hypoxia inducible factor 1 (HIF-1) independent manner. TRIB3 induction after hypoxia did not increase with decreasing oxygen levels. In breast tumor xenografts and human breast cancer tissues TRIB3 co-localized with the hypoxic cell marker pimonidazole. The induction of TRIB3 by hypoxia was shown to be regulated via the PERK/ATF4/CHOP pathway of the unfolded protein response and knockdown of TRIB3 resulted in a dose-dependent increase in hypoxia sensitivity. CONCLUSIONS: TRIB3 is independently associated with poor prognosis of breast cancer patients, possibly through its association with tumor cell hypoxia.

ACR appropriateness Criteria® pretreatment evaluation and follow-up of endometrial cancer of the uterus.

Endometrial cancer is one of the common malignancies in the female genital tract. Imaging in pretreatment evaluation may play an important role in an assessment of morphological prognostic factors including tumor size, depth of myometrial invasion, endocervical extent, and lymph node status. Imaging is also useful in posttreatment evaluation of patients with clinically suspected recurrence. Various modalities including MRI, CT ultrasound and FDG PET-CT-CT have been used for evaluation of the endometrial cancer in both before and after treatment settings. Literature on the indications and usefulness of these imaging studies for endometrial cancer is reviewed.

Stereotactic body radiotherapy (SBRT): Technological innovation and application in gynecologic oncology.

OBJECTIVES: Stereotactic body radiotherapy (SBRT) is a novel form of noninvasive, highly conformal radiation treatment that delivers a high dose to tumor. The advantage of the technique resides in its ability to provide a high dose to tumor but spare normal tissues to an extent not previously possible. In this paper we will provide an introduction and review of this technology with regard to its use in gynecologic malignancies. Preliminary results from our experience are presented for the purpose of illustrating the range of SBRT applications in gynecologic oncology. METHODS: A comprehensive literature review was conducted and our experience from the past three years was reviewed. RESULTS: Six case series are published that report results of SBRT for gynecologic malignancies. Sixteen gynecologic patients have been treated with SBRT at our institution. Treatment sites include pelvic and periaortic nodes (9 patients), oligometastatic disease (2), and cervical or endometrial primary tumors when other conventional external radiation or brachytherapy techniques were unsuitable (5). Preliminary follow-up at a median of 11 months (range, 0.3-33 months) demonstrates 79% locoregional control, 43% distant failure, and 50% overall survival. CONCLUSIONS: SBRT boosts to macroscopic periaortic node recurrences and other sites seem to provide local control and a possibility of long-term disease-free survival in carefully selected patients. Previously this had been difficult to achieve with conventional radiotherapy because of the proximity of periaortic nodes to small bowel. SBRT also offers a novel approach for minimally invasive treatment in the management of gynecological cancer where current surgical and radiotherapy techniques are unsuitable.

Hypoxia and differentiation in squamous cell carcinomas of the uterine cervix: pimonidazole and involucrin.

PURPOSE: Pimonidazole binding (hypoxia) and involucrin expression (differentiation) overlap extensively in squamous cell carcinomas. This study asks whether involucrin might serve as an endogenous marker for tumor hypoxia. A second question is whether differentiation affects hypoxia-inducible metallothionein (MT) expression in normal human epithelia and squamous cell carcinomas as it does in rodent epithelia. EXPERIMENTAL DESIGN: Thirty-four patients with squamous cell carcinoma of the uterine cervix were infused with pimonidazole hydrochloride solution. The next day, multiple biopsies were formalin-fixed, paraffin-embedded and sectioned at 4 micro m. Qualitative and quantitative analyses for involucrin expression, pimonidazole binding, and human MT-IIa mRNA expression were performed. RESULTS: No overall correlation between the extent of involucrin expression and pimonidazole binding was observed. The lack of correlation was because of heterogeneous patterns of immunostaining for involucrin generally related to tumor grade. Colocalized immunostaining for involucrin and pimonidazole binding was observed in intermediate grade tumors but not in well-differentiated or poorly differentiated tumors. Human MT-IIa mRNA and MT protein were expressed in basal lamina of normal human epithelia and in the proliferative rims of tumor nests. CONCLUSIONS: Colocalization of immunostaining for involucrin and pimonidazole binding is consistent with oxygen regulation, but the lack of involucrin expression in hypoxic regions of poorly differentiated tumors indicates that its transcriptional status with respect to hypoxia induction is altered by cell differentiation. The localization of MT message and protein in the outer rims of most tumor nests indicates that the transcriptional status of metallothionein is also altered by differentiation.

Intraperitoneal radioactive phosphorus (32P) versus observation after negative second-look laparotomy for stage III ovarian carcinoma: a randomized trial of the Gynecologic Oncology Group.

PURPOSE: The objectives of this prospective randomized study of consolidation therapy were to evaluate recurrence-free survival (RFS), overall survival (OS), and the morbidity of intraperitoneal (IP) chromic phosphate suspension (32P) therapy in patients with stage III epithelial ovarian carcinoma who have no detectable evidence of disease at the second-look laparotomy (SLL) procedure after primary chemotherapy. PATIENTS AND METHODS: In a multi-institution clinical cooperative trial, 202 eligible patients with a negative SLL were randomly selected to receive either 15 mCi IP 32P (n = 104) or no further therapy (NFT; n = 98). RESULTS: With a median follow-up of 63 months in living patients, 68 patients in the IP 32P group (65%) and 63 patients in the NFT group (64%) have developed tumor recurrence. The relative risk of recurrence is 0.90 (IP 32P to NFT) (90% confidence interval [CI], 0.68 to 1.19). The 5-year RFS rate is 42% and 36% for the IP 32P and NFT groups, respectively; the difference is not statistically significant (log-rank test, P =.27). There was no statistically significant difference in OS (P =.19). The relative risk of death is 0.85 (IP 32P to NFT) (90% CI, 0.62 to 1.16). Sixteen patients (8%) experienced grade 3 or 4 adverse effects, with eight in each respective group. CONCLUSION: Intraperitoneal chromic phosphate did not decrease the risk of relapse or improve survival for patients with stage III epithelial ovarian cancer after a negative SLL. Despite complete pathologic remission at SLL after initial surgery and platinum-based chemotherapy, 61% of stage III ovarian cancer patients had tumor recurrence within 5 years of negative SLL. This indicates a need for more effective initial therapy and further studies of consolidation therapy.

HIF-1A, pimonidazole, and iododeoxyuridine to estimate hypoxia and perfusion in human head-and-neck tumors.

PURPOSE: Tumor hypoxia measured by microelectrodes has been shown to indicate poor patient outcome. Here we investigated four potentially more widely applicable immunohistochemical parameters of tumor oxygenation and perfusion in human head-and-neck tumors. METHODS: Twenty patients with squamous cell carcinomas of the head and neck treated with primary surgery were injected with pimonidazole and IdUrd the evening before operation. Consecutive paraffin-embedded sections were stained for blood vessels, pimonidazole, IdUrd, and HIF-1alpha. IdUrd labeling and Ki-67 labeling around individual blood vessels were scored. The spatial relationship between HIF-1alpha and pimonidazole was studied, as well as the distribution of both markers as a function of distance from the nearest blood vessel. RESULTS: Measurement of all four parameters (diffusion-limited fraction, pimonidazole fraction, HIF-1alpha fraction, IdUrd-negative vessels) was feasible, and a significant difference between tumors was found for all parameters. IdUrd-labeled cells were absent around some vessels, indicating lack of perfusion, because these regions were positive for Ki-67. There was a positive correlation between diffusion-limited fraction and pimonidazole area for all images from all tumors, although no correlation for mean values per tumor. Colocalization of pimonidazole and HIF-1alpha was low (0.02%-25%). Most expression profiles showed a more homogenous distribution for HIF-1alpha than pimonidazole. There was no significant correlation between the pimonidazole and HIF-1alpha fractions in the 10 tumors studied. CONCLUSIONS: Simultaneous immunohistochemical measurements related to hypoxia and perfusion are feasible (and easily applicable) in resected human tumors. The different geographic distributions of HIF-1alpha and pimonidazole indicate that HIF-1alpha might not be suitable as a marker for chronic hypoxia. Each parameter will be correlated with outcome in a larger ongoing study on head-and-neck tumors treated with surgery with or without postoperative radiotherapy.

Functional significance of erythropoietin receptor expression in breast cancer.

Erythropoietin (EPO) is the principal hematopoietic cytokine that regulates mammalian erythropoiesis by binding to its transmembrane receptor EpoR. Recent experimental evidence suggests that the biologic effects of EPO are not limited to the regulation of erythropoiesis. In studies focusing on nonhematopoietic effects of EpoR signaling, we found high levels of EpoR protein expression in human breast cancer cells. The purpose of the present study was to evaluate clinical breast cancer specimens for EPO and EpoR expression, characterize the relationship between EPO expression and tumor hypoxia in biopsies prelabeled with hypoxia marker pimonidazole, analyze breast cancer cell lines for EpoR expression, and study the functional significance of EpoR expression in breast cancer cells in vivo. Immunohistochemical analysis for EPO, EpoR expression, and pimonidazole adducts was performed on 26 tumor biopsies with contiguous sections from 10 patients with breast cancer. High levels of EpoR expression were found in cancer cells in 90% of tumors. EPO expression was found in 60% of tumors and EPO and EpoR colocalization in tumor cells was present in many cases. The expression pattern of EPO with respect to tumor hypoxia was variable, without consistent colocalization of EPO and hypoxia in tumor cells. Human and rat breast cancer tissue culture cells express EpoR mRNA and protein. To study the in vivo function of EpoR expression in breast cancer cells, we used rat syngeneic R3230Ac mammary adenocarcinoma cells in a tumor Z-chamber model (dual porous plexiglass chambers containing fibrin gel, cancer cells, and a putative anti-tumor compound implanted into the subcutaneous tissue of rats). Local, one-time administration of a neutralizing anti-EPO antibody, soluble EPO receptor, or an inhibitor of Jak2, a cytoplasmic tyrosine kinase essential for EPO-mediated mitogenesis, resulted in a delay in tumor growth with 45% reduction in maximal tumor depth in tumor Z-chambers in a dose-dependent manner. These studies demonstrate the expression of functional receptors for EPO in breast cancer cells.