Prospective comparison of positron emission tomography (PET)/magnetic resonance and PET/computed tomography dosimetry in hepatic malignant neoplastic disease after 90Y radioembolization treatment.

Background: 90Y radioembolization is an established treatment modality for hepatic malignancies. Successful radioembolization requires optimal dose delivery to tumors while minimizing dosages to parenchyma. Post-treatment positron emission tomography (PET)/computed tomography (CT) dosimetry is the established benchmark, whereas PET/magnetic resonance (MR) is an emerging modality. The goal of this study was to assess the intermodality agreement between PET/MR and PET/CT 90Y dosimetry. Methods: In this single-institution study, 18 patients (20 treatment sessions) with a primary or metastatic hepatic malignancy underwent both PET/MR and PET/CT after 90Y radioembolization. Patients were randomized to undergo one modality first, followed by the other. The region of interest was delineated using MR images and tumor and liver dosimetry was calculated. Intermodality agreement was assessed using the Bland-Altman method. A generalized linear model was used to assess the effect of baseline variables on intermodality dose differences. Results: PET/MR underestimated tumor and liver absorbed doses when compared to PET/CT by -3.7% (P=0.042) and -5.8% (P=0.029), respectively. A coverage probability plot demonstrated that 80% and 90% of tumor dose measurements fell within intermodality differences of 11% and 18%, respectively. PET/MR underestimated tumor dose at both low (<1 GBq) and high (>3 GBq) injected activity levels (P<0.001) by -22.3 [standard deviation (SD) =13.5] and -24.3 (SD =18.7), respectively. Conclusions: Although PET/MR significantly underestimated the absorbed dose when compared to PET/CT, the intermodality agreement was high and the degree of underestimation was better than previously reported. Intermodality differences were more pronounced at low and high injected doses. Additional studies are required to assess the clinical implications of these findings.

Prediction of Mortality and Hepatic Encephalopathy after Transjugular Intrahepatic Portosystemic Shunt Placement: Baseline and Longitudinal Body Composition Measurement.

PURPOSE: To investigate effects of baseline and early longitudinal body composition changes on mortality and hepatic encephalopathy (HE) after transjugular intrahepatic portosystemic shunt (TIPS). MATERIALS AND METHODS: This is a case-control study with analysis of a TIPS registry (1995-2020) including data from patients with cirrhosis with computed tomography (CT) scans obtained within 1 month before and 3 months after TIPS. Core muscle area (CMA), macroscopic subcutaneous adipose tissue (mSAT), macroscopic visceral adipose tissue (mVAT) area, and muscle adiposity index (MAI) on CT were obtained. Multipredictor Cox proportional hazards models were used to assess the effect of body composition variables on mortality or HE. RESULTS: In total, 280 patients (158 men; median age, 57.0 years; median Model for End-stage Liver Disease-sodium [MELD-Na] score, 14.0) were included. Thirty-four patients had post-TIPS imaging. Median baseline CMA was 68.3 cm2 (interquartile range, 57.7-83.5 cm2). Patients with higher baseline CMA had decreased risks of mortality (hazard ratio [HR]: 0.82; P = .04) and HE (HR: 0.82; P = .009). It improved prediction of mortality over MELD-Na and post-TIPS right atrial pressure alone (confidence interval = 0.729). An increase in CMA (HR: 0.60; P = .043) and mSAT (HR: 0.86; P = .022) or decrease in MAI (HR: 1.50; P = .049) from before to after TIPS was associated with a decreased risk of mortality. An increase in mSAT was associated with an increased risk of HE (HR: 1.11; P = .04). CONCLUSIONS: CMA on CT scan 1 month before TIPS placement predicts mortality and HE in patients with cirrhosis. Changes in body composition on CT measured 3 months after TIPS placement independently predict mortality and HE.

Gastrointestinal malignancies in pregnancy.

Gastrointestinal malignancies, though uncommon in pregnancy, present several unique challenges with regards to diagnosis, staging, and treatment. Imaging the pregnant patient with a suspected or confirmed GI malignancy requires modifications to the radiologic modality of choice and protocol in order to minimize harm to the fetus, ensure accuracy in diagnosis and staging and guide treatment decisions. In this review article, we discuss the imaging approach to the pregnant patient with GI cancer, including safe radiologic modalities and modifications to imaging protocols. We also review the most common GI cancers encountered in pregnancy, including colorectal, pancreatic, gastric, and small bowel tumors, with emphasis to imaging findings, staging, and treatment considerations.

Association between CT-based body composition assessment and patient outcomes during neoadjuvant chemotherapy for epithelial ovarian cancer.

OBJECTIVE: The aim of this study was to characterize the body composition of patients undergoing neoadjuvant chemotherapy (NACT) for epithelial ovarian cancer (EOC), identify factors associated with sarcopenia at diagnosis, and evaluate the impact of pretreatment sarcopenia and changes in body composition parameters during therapy on perioperative and disease-related outcomes. METHODS: Patients undergoing NACT for EOC between 2008 and 2020 were identified. Pre-treatment and post-treatment contrast-enhanced CT scans were reviewed to determine skeletal muscle index (SMI) and visceral adipose tissue (VAT) area at the mid-fourth lumbar vertebral level. SMI and VAT were analyzed for association with clinical and treatment variables. RESULTS: 174 patients were identified. Mean pretreatment SMI and VAT were 38.3 cm2/m2 ± 7.9 and 51.2 cm2/m2 ± 34.3, respectively. Comparatively, mean post-treatment SMI and VAT were 37.8 cm2/m2 ± 7.9 and 43.7 cm2/m2 ± 29.7, respectively. Most patients exhibited an overall decrease in SMI from pretreatment to posttreatment scans. Caucasian race, older age, and lower body mass index at diagnosis were associated with lower pretreatment SMI. Lower pre-treatment SMI was associated with lower surgical complexity scores (p < 0.001) and estimated blood loss (p = 0.029). Decrease in SMI after NACT was associated with increased rates of ICU admissions and length of stay. While there was no association between SMI and overall survival (OS) or progression-free survival (PFS), >2% decrease per 100 days in VAT was significantly associated with worse OS. CONCLUSIONS: Patients with lower pretreatment SMI tend to undergo less complex surgery than those with higher SMI despite NACT. Decrease in VAT may be a potential indicator of worse OS. Information on body composition can aid in clinical decision making in patients with EOC.

Changes in abdominal adipose tissue depots assessed by MRI correlate with hepatic histologic improvement in non-alcoholic steatohepatitis.

BACKGROUND & AIMS: Non-alcoholic steatohepatitis (NASH) is prevalent in adults with obesity and can progress to cirrhosis. In a secondary analysis of prospectively acquired data from the multicenter, randomized, placebo-controlled FLINT trial, we investigated the relationship between reduction in adipose tissue compartment volumes and hepatic histologic improvement. METHODS: Adult participants in the FLINT trial with paired liver biopsies and abdominal MRI exams at baseline and end-of-treatment (72 weeks) were included (n = 76). Adipose tissue compartment volumes were obtained using MRI. RESULTS: Treatment and placebo groups did not differ in baseline adipose tissue volumes, or in change in adipose tissue volumes longitudinally (p = 0.107 to 0.745). Deep subcutaneous adipose tissue (dSAT) and visceral adipose tissue volume reductions were associated with histologic improvement in NASH (i.e., NAS [non-alcoholic fatty liver disease activity score] reductions of ≥2 points, at least 1 point from lobular inflammation and hepatocellular ballooning, and no worsening of fibrosis) (p = 0.031, and 0.030, respectively). In a stepwise logistic regression procedure, which included demographics, treatment group, baseline histology, baseline and changes in adipose tissue volumes, MRI hepatic proton density fat fraction (PDFF), and serum aminotransferases as potential predictors, reductions in dSAT and PDFF were associated with histologic improvement in NASH (regression coefficient = -2.001 and -0.083, p = 0.044 and 0.033, respectively). CONCLUSIONS: In adults with NASH in the FLINT trial, those with greater longitudinal reductions in dSAT and potentially visceral adipose tissue volumes showed greater hepatic histologic improvements, independent of reductions in hepatic PDFF. CLINICAL TRIAL NUMBER: NCT01265498. IMPACT AND IMPLICATIONS: Although central obesity has been identified as a risk factor for obesity-related disorders including insulin resistance and cardiovascular disease, the role of central obesity in non-alcoholic steatohepatitis (NASH) warrants further clarification. Our results highlight that a reduction in central obesity, specifically deep subcutaneous adipose tissue and visceral adipose tissue, may be related to histologic improvement in NASH. The findings from this analysis should increase awareness of the importance of lifestyle intervention in NASH for clinical researchers and clinicians. Future studies and clinical practice may design interventions that assess the reduction of deep subcutaneous adipose tissue and visceral adipose tissue as outcome measures, rather than simply weight reduction.

Disseminated Metacestode Versteria Species Infection in Woman, Pennsylvania, USA1.

A patient in Pennsylvania, USA, with common variable immunodeficiency sought care for fever, cough, and abdominal pain. Imaging revealed lesions involving multiple organs. Liver resection demonstrated necrotizing granulomas, recognizable tegument, and calcareous corpuscles indicative of an invasive cestode infection. Sequencing revealed 98% identity to a Versteria species of cestode found in mink.

Hepatic R2* is more strongly associated with proton density fat fraction than histologic liver iron scores in patients with nonalcoholic fatty liver disease.

BACKGROUND: The liver R2* value is widely used as a measure of liver iron but may be confounded by the presence of hepatic steatosis and other covariates. PURPOSE: To identify the most influential covariates for liver R2* values in patients with nonalcoholic fatty liver disease (NAFLD). STUDY TYPE: Retrospective analysis of prospectively acquired data. POPULATION: Baseline data from 204 subjects enrolled in NAFLD/NASH (nonalcoholic steatohepatitis) treatment trials. FIELD STRENGTH: 1.5T and 3T; chemical-shift encoded multiecho gradient echo. ASSESSMENT: Correlation between liver proton density fat fraction and R2*; assessment for demographic, metabolic, laboratory, MRI-derived, and histological covariates of liver R2*. STATISTICAL TESTS: Pearson's and Spearman's correlations; univariate analysis; gradient boosting machines (GBM) multivariable machine-learning method. RESULTS: Hepatic proton density fat fraction (PDFF) was the most strongly correlated covariate for R2* at both 1.5T (r = 0.652, P < 0.0001) and at 3T (r = 0.586, P < 0.0001). In the GBM analysis, hepatic PDFF was the most influential covariate for hepatic R2*, with relative influences (RIs) of 61.3% at 1.5T and 47.5% at 3T; less influential covariates had RIs of up to 11.5% at 1.5T and 16.7% at 3T. Nonhepatocellular iron was weakly associated with R2* at 3T only (RI 6.7%), and hepatocellular iron was not associated with R2* at either field strength. DATA CONCLUSION: Hepatic PDFF is the most influential covariate for R2* at both 1.5T and 3T; nonhepatocellular iron deposition is weakly associated with liver R2* at 3T only. LEVEL OF EVIDENCE: 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1456-1466.

Prognostic value of pre-transplant PET/CT in patients with diffuse large B-cell lymphoma undergoing autologous stem cell transplantation.

Pre-transplant PET/CT may be prognostic in diffuse large B-cell lymphoma (DLBCL) patients undergoing autologous stem cell transplantation (ASCT). We reviewed relapsed and pre-transplant PET/CT scans of 32 patients with DLBCL treated with ASCT to determine the Deauville score and the maximum standardized uptake value (SUVmax). Patients with a Deauville score of 4 had a significantly inferior prognosis. The 3-year progression-free survival (PFS) for patients with Deauville 1-3 score was 64%, compared to 0% for Deauville 4, while the 3-year overall survival (OS) was 84% and 25%, respectively (p < .001, p = .002). The change in the SUVmax (>66 versus ≤66%) was not predictive of PFS or OS, but a high pre-transplant SUVmax (>6) demonstrated a trend towards an inferior PFS. Pre-transplant PET/CT is a tool for identifying DLBCL patients at high risk for treatment failure with ASCT and could be used to risk-stratify patients in prospective clinical trials of novel transplant strategies.

Applications of PET/MR Imaging in Urogynecologic and Genitourinary Cancers.

Positron emission tomograph (PET)-magnetic resonance (MR) is a new modality combining PET and MR. In gynecologic cancers it can be used for staging of cervical and endometrial cancer, planning of radiation therapy in cervical cancer, assessing response to chemotherapy in ovarian cancer, and detection of recurrence in most gynecologic cancers. It is being explored for prostate cancer and other genitourinary cancers, but is still in experimental stages.

PET/MR Imaging of Multiple Myeloma.

PET-magnetic resonance (MR) is a hybrid imaging modality that combines PET and MR. Evidence for this new modality is in the process of being developed, but both component modalities are well tested in the diagnosis and management of multiple myeloma. It allows advanced bimodality imaging of the whole body with an adaptable field of view and it can be used for monitoring plasma cell dyscrasias for progression to multiple myeloma, for assessing disease burden in patients with known multiple myeloma, for assessing response to therapy and relapse after remission, and for radiation therapy treatment planning.

Do myocardial PET-MR and PET-CT FDG images provide comparable information?

INTRODUCTION: Although positron emission tomography PET-MR imaging is emerging into clinical practice, many aspects of this imaging technique such as attenuation correction have yet to be validated for myocardial imaging. Thus, it is uncertain whether PET-MR FDG images provide clinical information which is comparable to PET-CT FDG images. The study goal was to systematically compare relative myocardial FDG concentrations obtained from cardiac PET-MR images to those derived from same day PET-CT images. METHODS: Myocardial FDG images of 27 patients undergoing PET-CT imaging, followed by PET-MR imaging 42 ± 13 minutes later as part of a prospective oncology study were analyzed. Mean segmental standardized uptake measurements (SUVmean) were obtained in each of the 17 standard myocardial segments and normalized to the brightest segment. RESULTS: Normalized segmental SUVmean values did not differ significantly between the PET-MR and PET-CT images (mean difference 0.002, P = .826). The specific segment was a marginally significant predictor of the differences (P = .057), with the largest difference in the anteroseptal basal segment. CONCLUSIONS: PET-MR, vis-à-vis PET-CT, does not significantly raise segmental uptake relative to the brightest segment, suggesting that PET-MR can be used similarly to PET-CT for applications where relative uptake is important.

Hybrid PET/MR imaging: physics and technical considerations.

In just over a decade, hybrid imaging with FDG PET/CT has become a standard bearer in the management of cancer patients. An exquisitely sensitive whole-body imaging modality, it combines the ability to detect subtle biologic changes with FDG PET and the anatomic information offered by CT scans. With advances in MR technology and advent of novel targeted PET radiotracers, hybrid PET/MRI is an evolutionary technique that is poised to revolutionize hybrid imaging. It offers unparalleled spatial resolution and functional multi-parametric data combined with biologic information in the non-invasive detection and characterization of diseases, without the deleterious effects of ionizing radiation. This article reviews the basic principles of FDG PET and MR imaging, discusses the salient technical developments of hybrid PET/MR systems, and provides an introduction to FDG PET/MR image acquisition.

Practical guide for implementing hybrid PET/MR clinical service: lessons learned from our experience.

Positron emission tomography (PET) and magnetic resonance imaging, until recently, have been performed on separate PET and MR systems with varying temporal delay between the two acquisitions. The interpretation of these two separately acquired studies requires cognitive fusion by radiologists/nuclear medicine physicians or dedicated and challenging post-processing. Recent advances in hardware and software with introduction of hybrid PET/MR systems have made it possible to acquire the PET and MR images simultaneously or near simultaneously. This review article serves as a road-map for clinical implementation of hybrid PET/MR systems and briefly discusses hardware systems, the personnel needs, safety and quality issues, and reimbursement topics based on experience at NYU Langone Medical Center and Cleveland Clinic.

Techniques, benefits, and challenges of PET-MR.

Positron emission tomography (PET) scans can now be acquired in unison with magnetic resonance (MR) scans as a single resource. This hybrid PET-MR solution combines the anatomic detail and functional data of MR scans with the biologic or physiological information offered by PET scans. This article describes aspects of implementing a PET-MR imaging program, including various technical and operational challenges, scheduling and workflow solutions, room construction and equipment, and finally clinical applications of this novel modality. The Directed Reading also discusses the possible future role of PET-MR in the clinical setting.

Tumor size is an independent predictor of lymph node metastasis and survival in early stage endometrioid endometrial cancer.

OBJECTIVE(S): To analyze the impact of tumor size (TS) on risk of lymph node metastasis (PLN) and prognosis in endometrioid endometrial cancer grossly confined to the uterus (EEC). METHOD(S): Patients with EEC grossly confined to the uterus were identified from Surveillance, Epidemiology, and End Results dataset from 1988 to 2007. Only surgically treated patients were included. TS was analyzed as a continuous and categorical variable (TS ≤ 2 cm, >2-5 cm and >5 cm). Multivariable logistic regression and Cox proportional hazards models were used. RESULT(S): 19,692 patients met the inclusion criteria. In patients with TS ≤ 2 cm, only 2.7 % (88/3,244) had PLN; this increased to 5.8 % (372/6,355) with TS > 2-5 cm and 11.1 % (195/1,745) with TS > 5 cm. The odds of PLN increased by 14 % for each 1 cm increase in TS after controlling for age, race, depth of myometrial invasion and grade (HR 1.14, 95 % CI 1.10-1.19, p < 0.001). Further, TS was an independent predictor of disease-specific survival (DSS) even after adjusting for age, race, grade, depth of myometrial invasion, lymph node status and adjuvant radiation therapy (HR 1.13 for each 1 cm increment in TS, 95 % 1.08-1.18, p < 0.001). In multivariable analysis, larger TS (>5 cm) was significantly associated with worse DSS (HR 2.09, 95 % 1.31-3.35, p = 0.002); however, there was no significant difference between TS > 2-5 cm versus ≤2 cm (HR 1.25, 95 % 0.85-1.83, p = 0.25). The impact of TS remained significant on DSS in subset of patients who underwent lymphadenectomy with negative lymph nodes. CONCLUSION(S): TS was an independent predictor of lymph node metastasis and disease-specific survival in patients with EEC grossly confined to the uterus. Tumor >5 cm was a predictor of disease-specific survival but no difference in outcome was noted between tumor >2-5 cm and tumor ≤2 cm.

Determination of Radiation Absorbed Dose to Primary Liver Tumors and Normal Liver Tissue Using Post-Radioembolization (90)Y PET.

BACKGROUND: Radioembolization with Yttrium-90 ((90) Y) microspheres is becoming a more widely used transcatheter treatment for unresectable hepatocellular carcinoma (HCC). Using post-treatment (90) Y positron emission tomography/computerized tomography (PET/CT) scans, the distribution of microspheres within the liver can be determined and quantitatively assessed. We studied the radiation dose of (90) Y delivered to liver and treated tumors. METHODS: This retrospective study of 56 patients with HCC, including analysis of 98 liver tumors, measured and correlated the dose of radiation delivered to liver tumors and normal liver tissue using glass microspheres (TheraSpheres(®)) to the frequency of complications with modified response evaluation criteria in solid tumors (mRECIST). (90) Y PET/CT and triphasic liver CT scans were used to contour treated tumor and normal liver regions and determine their respective activity concentrations. An absorbed dose factor was used to convert the measured activity concentration (Bq/mL) to an absorbed dose (Gy). RESULTS: The 98 studied tumors received a mean dose of 169 Gy (mode 90-120 Gy; range 0-570 Gy). Tumor response by mRECIST criteria was performed for 48 tumors that had follow-up scans. There were 21 responders (mean dose 215 Gy) and 27 non-responders (mean dose 167 Gy). The association between mean tumor absorbed dose and response suggests a trend but did not reach statistical significance (p = 0.099). Normal liver tissue received a mean dose of 67 Gy (mode 60-70 Gy; range 10-120 Gy). There was a statistically significant association between absorbed dose to normal liver and the presence of two or more severe complications (p = 0.036). CONCLUSION: Our cohort of patients showed a possible dose-response trend for the tumors. Collateral dose to normal liver is non-trivial and can have clinical implications. These methods help us understand whether patient adverse events, treatment success, or treatment failure can be attributed to the dose that the tumor or normal liver received.

Detection of urolithiasis: comparison of 100% tube exposure images reconstructed with filtered back projection and 50% tube exposure images reconstructed with sinogram-affirmed iterative reconstruction.

PURPOSE: To compare images acquired with 50% tube exposure with a dual-source computed tomographic (CT) scanner and reconstructed with sinogram-affirmed iterative reconstruction (SAFIRE) with 100% exposure images reconstructed with filtered back projection (FBP) for reader ability to detect stones, reader confidence, and findings outside the urinary tract. MATERIALS AND METHODS: In this HIPAA-compliant, institutional review board-approved study, imaging examinations in 99 patients with urolithiasis were assessed. Data from both tubes were reconstructed with FBP; data from the primary tube only were reconstructed with SAFIRE. Seven readers evaluated randomized studies for calculi in nine regions. Reader confidence was scored by using a five-point scale. Ancillary findings were noted. Nonparametric methods for clustered data were used to estimate the area under the receiver operating characteristic curves with 95% confidence intervals to test for noninferiority of 50% exposure with SAFIRE. RESULTS: Calculi were found in 113 locations (pyelocalyceal ureter, 86; proximal ureter, seven; midureter, four; distal ureter, 15; bladder, one) and not found in 752 locations. Mean area under the receiver operating characteristic curve for FBP was 0.879 (range, 0.607-0.967) and for SAFIRE, 0.883 (range, 0.646-0.971; 95% confidence interval: -0.025, 0.031). The SAFIRE images were not significantly inferior to FBP images (P = .001). Reader confidence levels for images with stones were similar with FBP and SAFIRE (P = .963). For the 52 patients who had extraurinary findings, readers reported them correctly in 74.4% (271 of 364) and 72.0% (262 of 364) of cases (P = .215) for FBP and SAFIRE, respectively. For the nine patients with potentially important findings per the reference standard, the detection rates were 44% (28 of 63) and 33% (21 of 63, P = .024), respectively. For the 43 patients with unimportant or likely unimportant findings, the false detection rates were 15% (44 of 301) and 14% (43 of 301, P = .756), respectively. CONCLUSION: The 50% tube exposure CT images reconstructed with SAFIRE were not inferior to 100% exposure images reconstructed with FBP for diagnosis of urolithiasis, without decreases in reader confidence.

Post-liver transplantation sarcopenia in cirrhosis: a prospective evaluation.

BACKGROUND AND AIM: Pre-transplant sarcopenia (reduced skeletal muscle mass) predicts poor outcome in cirrhosis. In contrast, whether muscle mass increases post-orthotopic liver transplantation (OLT) is not known and was studied prospectively. METHODS: Consecutive patients who underwent a comprehensive nutritional evaluation in a liver transplant nutrition clinic were included. Core abdominal muscle area was measured on abdominal computed tomography obtained pre- and post-OLT. Age- and gender-based controls were used to define sarcopenia. Measures of body composition pre-transplant were correlated with computed tomography measurements. Predictors and clinical impact of post-OLT change in muscle area were examined. In three subjects post-OLT and three controls, expression of genes regulating skeletal muscle mass were quantified. RESULTS: During the study period, 53 patients (M:F 41:12; age 56.9 ± 7.5 years) were followed up after OLT for 19.3 ± 9 months. Five patients died and another five had acute graft rejection. Pre-OLT sarcopenia was present in 33 (66.2%). Pre-transplant clinical characteristics including Child's score, MELD score, and nutritional status or post-transplantation immunosuppression regimen did not predict post-transplant change in muscle mass. New onset post-OLT sarcopenia developed in 14 patients. Loss of muscle mass post-OLT increased risk of diabetes mellitus and a trend toward higher mortality. Skeletal muscle expression of myostatin was higher and that of ubiquitin proteasome proteolytic components lower post-OLT than in controls. CONCLUSIONS: Post-transplantation sarcopenia is common and could not be attributed to pre-transplant characteristics or the type or duration of post-OLT immunosuppression. Post-transplant sarcopenia contributes to adverse consequences and strategies targeting myostatin may be beneficial.

Computed tomography characteristics of unresectable primary renal cell carcinoma treated with neoadjuvant sunitinib.

UNLABELLED: Neoadjuvant sunitinib might downsize unresectable renal cell carcinoma (RCC) and enable nephrectomy in a subset of patients. After neoadjuvant sunitinib in 27 RCC patients, tumors were resected in 13 patients. Higher attenuation using computed tomography (CT) scans and favorable response according to Morphology, Attenuation, Size, and Structure (MASS) criteria after 2 cycles of sunitinib were independent predictors of subsequent tumor resection. INTRODUCTION: In patients with locally advanced and metastatic RCC, selection criteria for nephrectomy are imprecise. Neoadjuvant sunitinib might downsize unresectable tumors and enable nephrectomy. CT scans of unresectable primary RCCs before and after neoadjuvant sunitinib were retrospectively reviewed to identify radiographic features associated with patient selection for surgery. PATIENTS AND METHODS: CT scans of 27 patients with RCC (31 tumors) treated with neoadjuvant sunitinib were performed as part of a prospective clinical trial. After neoadjuvant sunitinib, tumors were surgically resected in 13 patients (17 tumors) and not resected in 14 patients (14 tumors). Response to treatment with sunitinib was assessed with Response Evaluation Criteria in Solid Tumors and MASS criteria. RESULTS: On the contrast-enhanced CT scan before nephrectomy compared with the baseline CT scan, 88% of resected tumors demonstrated decreased size (median decrease 26%; -2.0 cm; P < .001), 88% had decreased attenuation (median decrease 30%; -27 Hounsfield units; P = .004), and 76% had increased necrosis (P < .001). Response to sunitinib was significantly more favorable (according to MASS criteria) in resected than in nonresected tumors (P = .005). In addition, the degree of baseline necrosis was less in tumors subsequently resected than in nonresected tumors (P = .05). Multivariate analysis showed that higher tumor attenuation after 2 cycles of sunitinib therapy and a favorable response (MASS criteria) after 2 cycles of sunitinib therapy were independent predictors of subsequent tumor resection. CONCLUSION: In unresectable primary RCC tumors, changes in select CT parameters after 2 cycles of neoadjuvant sunitinib might be associated with the potential for surgical resection.