Impact of cachexia on disease recurrence and survival outcomes in endometrial cancer patients.

Objective: Cancer cachexia is progressive weight loss due to muscle/adipose tissue wasting and inadequate intake that occurs in response to malignancy. It is an independent predictor of disease recurrence and reduced survival in several cancers. However, cachexia's relationship with gynecologic malignancy outcomes has only been examined in small studies with limited follow-up and inconsistent definitions of cachexia. This study investigated the impact of cachexia on disease recurrence and overall survival in high-risk endometrial carcinoma patients. Methods: This retrospective cohort study examined data from patients with high-risk non-metastatic primary endometrial carcinoma treated at a single institution from 2015 to 2020. Treatment for all subjects included total hysterectomy, surgical staging, pelvic external beam radiotherapy with or without adjuvant chemotherapy. Radiation planning CT datasets were used to measure skeletal musculature at the L3 vertebral level. Skeletal muscle index (SMI) was defined as total L3 skeletal muscle cross sectional area (cm2)/height2 (m2), and cachexia was defined based on SMI. Results: 55 patients were eligible for analysis. Several SMI thresholds were used to define cachexia, and analysis was performed for each definition. Kaplan-Meier and Cox-proportional hazards regression analysis yielded no significant reduction in overall survival (OS) or progression-free survival (PFS) in patients with cachexia, regardless of threshold chosen. However, 4 of 13 definitions of cachexia showed significantly improved OS in patients without cachexia, relative to those with cachexia. There were no significant differences in disease recurrence. Conclusions: Cachexia as defined in this study was not associated with poor outcomes in endometrial carcinoma patients based on OS, PFS, or disease recurrence.

Impact of race and social determinants of health on outcomes in patients with aggressive B-cell NHL treated with CAR-T therapy.

ABSTRACT: Chimeric antigen receptor (CAR) T-cell (CAR-T) immunotherapy is an effective therapy for relapsed/refractory B-cell non-Hodgkin lymphoma (r/r B-NHL). However, data are limited on the impact of the convergence of race and social determinants of health on outcomes for patients treated with CAR-T therapy. We examined the impact of interactions between race and insurance type on health care use and outcomes in patients treated with CAR-T therapy for aggressive B-NHL. Adult patients with r/r B-NHL treated with CD19 CAR-Ts were identified between 2015 and 2021 across 13 US academic centers. Insurance type, demographic, and clinical data were collected and analyzed. In total, 466 adult patients were included in our analysis. Median follow-up after CAR-T therapy was 12.7 months. Median progression-free survival (mPFS) was longer for Caucasians (11.5 months) than for African Americans (3.5 months; hazard ratio [HR], 1.56 [1.03-2.4]; P = .04) or Asians (2.7 months; HR, 1.7 [1.02-2.67]; P = .04). Differences in median overall survival (mOS) were not significant. For Medicare (n = 206) vs Medicaid (n = 33) vs private insurance (n = 219) vs self-pay (n = 7): mPFS was 15.9 vs 4.2 vs 6.0 vs 0.9 months (P < .001), respectively; and mOS was 31.2 vs 12.8 vs 21.5 vs 3.2 months (P < .001), respectively. Our multicenter retrospective analysis showed that race and insurance status can affect outcomes for patients treated with CAR-T therapy.

Decreased bed mobility function is associated with post-discharge mortality for cancer patients in inpatient rehabilitation.

OBJECTIVE: The establishment of rehabilitation goals for hospitalized cancer patients depends on accurate medical prognosis and matching goals to clinical timelines. Current tools for estimating prognosis are limited. We hypothesized that bed mobility is a predictor of mortality in cancer patients admitted to inpatient rehabilitation. DESIGN: In a retrospective cohort of 187 subjects with non-neurologic cancer admitted to inpatient rehabilitation, Functional Independence Measure (FIM) scores and 6-month mortality were analyzed. RESULTS: In the cohort, survival rate was 71% at 6 months. In univariate analysis, discharge bed mobility score (OR = 0.75, 95%CI = 0.61 to 0.90, p = 0.003), bed mobility FIM gain (OR = 0.66, 95%CI = 0.51 to 0.85, p = 0.002), and bed mobility FIM efficiency (OR = 0.011, 95%CI = 0.00032 to 0.21, p = 0.006) were inversely associated with 6-month mortality after discharge from IRF. In multivariate analysis with additional motor FIM items, only bed mobility (OR = 0.73, 95%CI = 0.54 to 0.97, p = 0.029) and grooming (OR = 0.79, 95% CI = 0.63 to 0.99, p = 0.041) were independently associated with mortality. CONCLUSIONS: Lower discharge and lower change in bed mobility FIM scores are associated with mortality in cancer patients in inpatient rehabilitation. Bed mobility could serve as a clinical tool for estimating medical prognosis in hospitalized cancer patients and should be validated in prospective studies.

Harnessing the Systemic Biology of Functional Decline and Cachexia to Inform more Holistic Therapies for Incurable Cancers.

Options for treatment of incurable cancer remain scarce and are largely focused on limited therapeutic mechanisms. A new approach specific to advanced cancers is needed to identify new and effective treatments. Morbidity in advanced cancer is driven by functional decline and a number of systemic conditions, including cachexia and fatigue. This review will focus on these clinical concepts, describe our current understanding of their underlying biology, and then propose how future therapeutic strategies, including pharmaceuticals, exercise, and rehabilitation, could target these mechanisms as an alternative route to addressing incurable cancer.

Gait speed is a biomarker of cancer-associated cachexia decline and recovery.

Background: Progressive functional decline is a key element of cancer-associated cachexia. No therapies have successfully translated to the clinic due to an inability to measure and improve physical function in cachectic patients. Major barriers to translating pre-clinical therapies to the clinic include lack of cancer models that accurately mimic functional decline and use of non-specific outcome measures of function, like grip strength. New approaches are needed to investigate cachexia-related function at both the basic and clinical science levels. Methods: Survival extension studies were performed by testing multiple cell lines, dilutions, and vehicle-types in orthotopic implantation of K-ras LSL.G12D/+ ; Trp53 R172H/+ ; Pdx-1-Cre (KPC) derived cells. 128 animals in this new model were then assessed for muscle wasting, inflammation, and functional decline using a battery of biochemical, physiologic, and behavioral techniques. In parallel, we analyzed a 156-subject cohort of cancer patients with a range of cachexia severity, and who required rehabilitation, to determine the relationship between gait speed via six-minute walk test (6MWT), grip strength (hGS), and functional independence measures (FIM). Cachectic patients were identified using the Weight Loss Grading Scale (WLGS), Fearon consensus criteria, and the Prognostic Nutritional Index (PNI). Results: Using a 100-cell dose of DT10022 KPC cells, we extended the survival of the KPC orthotopic model to 8-9 weeks post-implantation compared to higher doses used (p<0.001). In this Low-dose Orthotopic (LO) model, both progressive skeletal and cardiac muscle wasting were detected in parallel to systemic inflammation; skeletal muscle atrophy at the fiber level was detected as early as 3 weeks post-implantation compared to controls (p<0.001). Gait speed in LO animals declined as early 2 week post-implantation whereas grip strength change was a late event and related to end of life. Principle component analysis (PCA) revealed distinct cachectic and non-cachectic animal populations, which we leveraged to show that gait speed decline was specific to cachexia (p<0.01) while grip strength decline was not (p=0.19). These data paralleled our observations in cancer patients with cachexia who required rehabilitation. In cachectic patients (identified by WLGS, Fearon criteria, or PNI, change in 6MWT correlated with motor FIM score changes while hGS did not (r 2 =0.18, p<0.001). This relationship between 6MWT and FIM in cachectic patients was further confirmed through multivariate regression (r 2 =0.30, p<0.001) controlling for age and cancer burden. Conclusion: Outcome measures linked to gait are better associated with cachexia related function and preferred for future pre-clinical and clinical cachexia studies.

Relationship Between Cachexia and the Functional Progress of Patients With Cancer in Inpatient Rehabilitation.

PURPOSE: Although inpatient rehabilitation can improve functional independence in patients with cancer, the role of cachexia in this population is unknown. Our objectives were to:1) Establish prevalence of cachexia in a cohort of cancer patients receiving inpatient rehabilitation and its association with demographic and oncological history.2) Determine the relationship between the presence of cachexia and functional recovery and whether these patients in inpatient rehabilitation have a distinct prognosis. METHODS: This is a retrospective cohort study of 250 patients over 330 admissions to an inpatient rehabilitation facility. Body weight loss threshold and Weight Loss Grading Scale identified patients with and without cachexia. Main outcomes were functional independence measure scores, discharge destination, and 6-mo survival. RESULTS: Prevalence of cachexia in inpatient rehabilitation was 59% using consensus body weight loss criteria, and 77% of cancer patients had a Weight Loss Grading Scale score greater than 0. Patients with and without cachexia had similar motor and cognitive gains, although patients with severe cachexia had more limited functional gains ( P < 0.05) and increased odds of acute care return ( P < 0.01). Patients with a Weight Loss Grading Scale score of 4 had decreased survival at 6 mos ( P < 0.05) compared with noncachectic patients. CONCLUSIONS: These data suggest that there is a relationship between cachexia and recovery for cancer patients that should be further studied in rehabilitation settings.

Peri-CAR-T practice patterns and survival predictors for all CAR-T patients and post-CAR-T failure in aggressive B-NHL.

Most patients receiving chimeric antigen receptor T-cell therapy (CAR-T) for aggressive B-cell non-Hodgkin lymphoma (B-NHL) do not experience a durable remission. Several novel agents are approved to treat relapsed, refractory aggressive B-NHL; however, it remains unclear how to sequence these therapies pre- and post-CAR-T. We conducted a multicenter retrospective analysis to describe peri-CAR-T practice patterns and survival predictors for patients receiving CD19-directed CAR-T. Patients (n = 514) from 13 centers treated with CAR-T for B-NHL between 2015-2021 were included in the study. Survival curves were constructed using Kaplan-Meier method. Multivariate Cox regression analysis was used to determine the impact of the variables on survival outcomes. For all patients receiving CAR-T, a greater number of lines of therapy pre-CAR-T apheresis and bridging therapy were predictive of inferior progression-free survival (PFS) and overall survival (OS). The median PFS and OS from the time of CAR-T cell infusion were 7.6 and 25.6 months, respectively. From the time of progression post-CAR-T, the median OS was 5.5 months. The median PFS of treatments administered in the first-line post-CAR-T failure was 2.8 months. Patients with refractory disease on day 30 had inferior OS and were less likely to receive subsequent treatment(s) than other patients with CAR-T failure. Allogeneic hematopoietic cell transplantation for selected patients at any time following CAR-T failure led to durable responses in over half of patients at 1 year. These data provide a benchmark for future clinical trials in patients with post-CAR-T cell progression, which remains an unmet clinical need.

A systematic review of pharmacologic treatment efficacy for depression in older patients with cancer.

Background: Older adults ≥65 years of age represent the majority of new cancer diagnoses and are vulnerable to developing depression-like symptoms. Evaluation and management of depression in older cancer patients is underappreciated despite its high prevalence and impact on health-related quality of life. Although antidepressants are the primary pharmacologics used to treat depressive-like symptoms, the efficacy and overall benefit(s) are not well-characterized in older adult patients with cancer. The objective of this investigation was to review what is known about the efficacy of pharmacologic treatment for older adults with depression and cancer. Methods: PubMed (Medline) and EMBASE (Elsevier) databases were analyzed for relevant literature in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: 1,919 unique studies were identified for title and abstract screening. Forty-eight publications were retrieved for full review. None of the identified studies evaluated the potential for benefit after pharmacological treatment among older adults with cancer and depression. Twenty-seven publications met all study criteria except for an analysis focused on older patients. Conclusion: We discovered a universal absence of literature with a relevance to pharmacologic antidepressant treatment effects in older adult patients with cancer. This included a lack of evaluation in patients with brain tumors who have an unusually high predilection for developing depression. Our findings suggest that new research is critically needed for understanding optimal clinical management strategies in older adults with cancer and depression who are treated with antidepressants.

Assessment of Cancer-Associated Cachexia - How to Approach Physical Function Evaluation.

PURPOSE OF REVIEW: Cachexia is a devastating syndrome that impacts a majority of cancer patients. Early assessment of cachexia is critical to implementing cachexia treatments. Our aim was to summarize the existing cachexia assessment tools for their utility in both symptom and function evaluation. RECENT FINDINGS: Several tools now exist that provide a symptom-based approach for evaluating weight change, appetite, and nutrition impact symptoms in cancer patients with cachexia. However, current instruments used to assess physical function changes related to cachexia are limited in depth and breadth. Instead, we recommend a tiered approach to cachexia-related functional assessment that involves evaluation of activities of daily living, general mobility, and exercise tolerance in a prioritized sequence. Current tools for cancer-associated cachexia assessment are adept at symptom evaluation. New approaches to physical function evaluation are needed that efficiently and broadly evaluate the diverse functional needs of cachexia patients.

Cachexia is a risk factor for negative clinical and functional outcomes in patients receiving chimeric antigen receptor T-cell therapy for B-cell non-Hodgkin lymphoma.

Cachexia is a muscle-wasting syndrome that is known to impact the clinical course of several cancer populations but has not been specifically investigated in patients receiving chimeric antigen receptor T (CAR-T) cell therapy. In this study, we investigated the relationship between cachexia markers and several cancer and functional outcomes in a pilot population of aggressive B-cell non-Hodgkin lymphoma patients receiving CAR-T. We found that the prognostic nutritional index was linked to progression-free survival, overall survival, and disability-free survival, while several additional weight and serum-based markers of cachexia were also associated with negative outcomes. These data prompt further investigation of cachexia markers in populations receiving CAR-T cell therapy.

Factors associated with unplanned transfers among cancer patients at a freestanding acute rehabilitation facility.

BACKGROUND: Cancer patients undergoing inpatient rehabilitation often have high risk of complications leading to unplanned transfer to acute care. Prior studies have identified factors associated with these transfers but have been limited to examining factors that pertain to initial admission to rehabilitation and were not conducted in a freestanding inpatient rehabilitation facility. OBJECTIVE: The study aimed to include these prerehabilitation factors in addition to factors upon initial assessment in rehabilitation. It was hypothesized that specific factors from each of these periods would be associated with unplanned transfer to acute care. DESIGN: Retrospective cohort study. SETTING: Freestanding academic inpatient rehabilitation facility affiliated with an academic tertiary care facility with a comprehensive cancer center. PATIENTS: Retrospective review of 330 specific encounters unique to 250 patients from March 2017 to September 2018. MAIN OUTCOME MEASURES: The outcome measure was unplanned transfer to acute care. A binary logistic regression model was used to examine the relationship between factors from oncologic history, acute care course, and factors upon admission to rehabilitation to unplanned transfer to acute care. RESULTS: From 330 encounters, there were 111 unplanned transfers (34%). Unplanned transfer to acute care was independently associated with gastrointestinal malignancy (odds ratio [OR] 4.4, p = .01), 6-minute walk test less than 90 m (OR 4.6, p = .003), and prior unplanned transfer (OR 3.5, p = .007). CONCLUSIONS: The study suggests that oncologic and functional prerehabilitation markers are associated with an increased likelihood of unplanned transfer during inpatient cancer rehabilitation. These findings will provide a framework for creating predictive tools for unplanned transfers in cancer rehabilitation patients.

Ultrasonographic comparison of the lateral epicondyle in wheelchair-user (and able-bodied) tennis players: A pilot study.

Objective: To evaluate whether manual wheelchair use and wheelchair tennis are associated with increased risk of lateral epicondylosis (LE). We hypothesized that the prevalence of LE would be highest in WC tennis players, followed by tennis players, WC users, and able-bodied subjects.Study design: Prospective cross-sectional pilot study.Setting: Milwaukee VAMC (clinic), National Veterans Wheelchair Games 2016 (medical event coverage).Participants: Wheelchair users, able-bodied controls, tennis players, non-tennis players.Interventions: Subjects meeting inclusion criteria underwent ultrasound examination of the dominant elbow evaluating for characteristics of LE (n = 83).Outcome measurements: Prevalence of LE between groups. Statistical analysis included odds ratios (OR), univariate and multivariate logistic regression.Results: There was no significant difference in diagnosis of LE between groups when comparing prevalence, unadjusted odds ratios, and predicted probabilities. When adjusted for age, able-bodied controls and tennis players had a similar increase in probability of LE with age; this effect was not seen for wheelchair users. Wheelchair users diagnosed with LE on US had spent significantly more time in a wheelchair (23 vs 13 years) than those with a negative diagnosis.Conclusions: Tennis playing in able bodied controls did not increase risk of LE. In wheelchair users, tennis playing does not appear to be associated with LE, though duration of wheelchair use appears to be a significant predictor of LE.Level of evidence: Level II.

Structural basis for chemokine recognition by a G protein-coupled receptor and implications for receptor activation.

Chemokines orchestrate cell migration for development, immune surveillance, and disease by binding to cell surface heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs). The array of interactions between the nearly 50 chemokines and their 20 GPCR targets generates an extensive signaling network to which promiscuity and biased agonism add further complexity. The receptor CXCR4 recognizes both monomeric and dimeric forms of the chemokine CXCL12, which is a distinct example of ligand bias in the chemokine family. We demonstrated that a constitutively monomeric CXCL12 variant reproduced the G protein-dependent and ß-arrestin-dependent responses that are associated with normal CXCR4 signaling and lead to cell migration. In addition, monomeric CXCL12 made specific contacts with CXCR4 that are not present in the structure of the receptor in complex with a dimeric form of CXCL12, a biased agonist that stimulates only G protein-dependent signaling. We produced an experimentally validated model of an agonist-bound chemokine receptor that merged a nuclear magnetic resonance-based structure of monomeric CXCL12 bound to the amino terminus of CXCR4 with a crystal structure of the transmembrane domains of CXCR4. The large CXCL12:CXCR4 protein-protein interface revealed by this structure identified previously uncharacterized functional interactions that fall outside of the classical "two-site model" for chemokine-receptor recognition. Our model suggests a mechanistic hypothesis for how interactions on the extracellular face of the receptor may stimulate the conformational changes required for chemokine receptor-mediated signal transduction.

Cancer cell chemokines direct chemotaxis of activated stellate cells in pancreatic ductal adenocarcinoma.

The mechanisms by which the extreme desmoplasia observed in pancreatic tumors develops remain unknown and its role in pancreatic cancer progression is unsettled. Chemokines have a key role in the recruitment of a wide variety of cell types in health and disease. Transcript and protein profile analyses of human and murine cell lines and human tissue specimens revealed a consistent elevation in the receptors CCR10 and CXCR6, as well as their respective ligands CCL28 and CXCL16. Elevated ligand expression was restricted to tumor cells, whereas receptors were in both epithelial and stromal cells. Consistent with its regulation by inflammatory cytokines, CCL28 and CCR10, but not CXCL16 or CXCR6, were upregulated in human pancreatitis tissues. Cytokine stimulation of pancreatic cancer cells increased CCL28 secretion in epithelial tumor cells but not an immortalized activated human pancreatic stellate cell line (HPSC). Stellate cells exhibited dose- and receptor-dependent chemotaxis in response to CCL28. This functional response was not linked to changes in activation status as CCL28 had little impact on alpha smooth muscle actin levels or extracellular matrix deposition or alignment. Co-culture assays revealed CCL28-dependent chemotaxis of HPSC toward cancer but not normal pancreatic epithelial cells, consistent with stromal cells being a functional target for the epithelial-derived chemokine. These data together implicate the chemokine CCL28 in the inflammation-mediated recruitment of cancer-associated stellate cells into the pancreatic cancer parenchyma.

Exploiting agonist biased signaling of chemokines to target cancer.

As knowledge of growth-independent functions of cancer cells is expanding, exploration into the role of chemokines in modulating cancer pathogenesis, particularly metastasis, continues to develop. However, more study into the mechanisms whereby chemokines direct the migration of cancer cells is needed before specific therapies can be generated to target metastasis. Herein, we draw attention to the longstanding conundrum in the field of chemokine biology that chemokines stimulate migration in a biphasic manner; and explore this phenomenon's impact on chemokine function in the context of cancer. Typically, low concentrations of chemokines lead to chemotactic migration and higher concentrations halt migration. The signaling mechanisms that govern this phenomenon remain unclear. Over the last decade, we have defined a novel signaling mechanism for regulation of chemokine migration through ligand oligomerization and biased agonist signaling. We provide insight into this new paradigm for chemokine signaling and discuss how it will impact future exploration into chemokine function and biology. In the pursuit of producing more novel cancer therapies, we suggest a framework for pharmaceutical application of the principles of chemokine oligomerization and biased agonist signaling in cancer. © 2016 Wiley Periodicals, Inc.

Pancreatic Cancer Cell Migration and Metastasis Is Regulated by Chemokine-Biased Agonism and Bioenergetic Signaling.

Patients with pancreatic ductal adenocarcinoma (PDAC) invariably succumb to metastatic disease, but the underlying mechanisms that regulate PDAC cell movement and metastasis remain little understood. In this study, we investigated the effects of the chemokine gene CXCL12, which is silenced in PDAC tumors, yet is sufficient to suppress growth and metastasis when re-expressed. Chemokines like CXCL12 regulate cell movement in a biphasic pattern, with peak migration typically in the low nanomolar concentration range. Herein, we tested the hypothesis that the biphasic cell migration pattern induced by CXCL12 reflected a biased agonist bioenergetic signaling that might be exploited to interfere with PDAC metastasis. In human and murine PDAC cell models, we observed that nonmigratory doses of CXCL12 were sufficient to decrease oxidative phosphorylation and glycolytic capacity and to increase levels of phosphorylated forms of the master metabolic kinase AMPK. Those same doses of CXCL12 locked myosin light chain into a phosphorylated state, thereby decreasing F-actin polymerization and preventing cell migration in a manner dependent upon AMPK and the calcium-dependent kinase CAMKII. Notably, at elevated concentrations of CXCL12 that were insufficient to trigger chemotaxis of PDAC cells, AMPK blockade resulted in increased cell movement. In two preclinical mouse models of PDAC, administration of CXCL12 decreased tumor dissemination, supporting our hypothesis that chemokine-biased agonist signaling may offer a useful therapeutic strategy. Our results offer a mechanistic rationale for further investigation of CXCL12 as a potential therapy to prevent or treat PDAC metastasis.

Cyclic AMP regulates the migration and invasion potential of human pancreatic cancer cells.

Aggressive dissemination and metastasis of pancreatic ductal adenocarcinoma (PDAC) results in poor prognosis and marked lethality. Rho monomeric G protein levels are increased in pancreatic cancer tissue. As the mechanisms underlying PDAC malignancy are little understood, we investigated the role for cAMP in regulating monomeric G protein regulated invasion and migration of pancreatic cancer cells. Treatment of PDAC cells with cAMP elevating agents that activate adenylyl cyclases, forskolin, protein kinase A (PKA), 6-Bnz-cAMP, or the cyclic nucleotide phosphodiesterase inhibitor cilostamide significantly decreased migration and Matrigel invasion of PDAC cell lines. Inhibition was dose-dependent and not significantly different between forskolin or cilostamide treatment. cAMP elevating drugs not only blocked basal migration, but similarly abrogated transforming-growth factor-ß-directed PDAC cell migration and invasion. The inhibitory effects of cAMP were prevented by the pharmacological blockade of PKA. Drugs that increase cellular cAMP levels decreased levels of active RhoA or RhoC, with a concomitant increase in phosphorylated RhoA. Diminished Rho signaling was correlated with the appearance of thickened cortical actin bands along the perimeter of non-motile forskolin or cilostamide-treated cells. Decreased migration did not reflect alterations in cell growth or programmed cell death. Collectively these data support the notion that increased levels of cAMP specifically hinder PDAC cell motility through F-actin remodeling.

CXM: a new tool for mapping breast cancer risk in the tumor microenvironment.

The majority of causative variants in familial breast cancer remain unknown. Of the known risk variants, most are tumor cell autonomous, and little attention has been paid yet to germline variants that may affect the tumor microenvironment. In this study, we developed a system called the Consomic Xenograft Model (CXM) to map germline variants that affect only the tumor microenvironment. In CXM, human breast cancer cells are orthotopically implanted into immunodeficient consomic strains and tumor metrics are quantified (e.g., growth, vasculogenesis, and metastasis). Because the strain backgrounds vary, whereas the malignant tumor cells do not, any observed changes in tumor progression are due to genetic differences in the nonmalignant microenvironment. Using CXM, we defined genetic variants on rat chromosome 3 that reduced relative tumor growth and hematogenous metastasis in the SS.BN3(IL2Rγ) consomic model compared with the SS(IL2Rγ) parental strain. Paradoxically, these effects occurred despite an increase in the density of tumor-associated blood vessels. In contrast, lymphatic vasculature and lymphogenous metastasis were unaffected by the SS.BN3(IL2Rγ) background. Through comparative mapping and whole-genome sequence analysis, we narrowed candidate variants on rat chromosome 3 to six genes with a priority for future analysis. Collectively, our results establish the utility of CXM to localize genetic variants affecting the tumor microenvironment that underlie differences in breast cancer risk.