Yong Yue

Four-dimensional MRI using three-dimensional radial sampling with respiratory self-gating to characterize temporal phase-resolved respiratory motion in the abdomen

To develop a four‐dimensional MRI (4D‐MRI) technique to characterize the average respiratory tumor motion for abdominal radiotherapy planning.

Identifying prognostic intratumor heterogeneity using pre- and post-radiotherapy 18F-FDG PET images for pancreatic cancer patients

BACKGROUND To stratify risks of pancreatic adenocarcinoma (PA) patients using pre- and post-radiotherapy (RT) PET/CT images, and to assess the prognostic value of texture variations in predicting therapy response of patients. METHODS Twenty-six PA patients treated with RT from 2011-2013 with pre- and post-treatment 18F-FDG-PET/CT scans were identified. Tumor locoregional texture was calculated using 3D kernel-based approach, and texture variations were identified by fitting discrepancies of texture maps of pre- and post-treatment images. A total of 48 texture and clinical variables were identified and evaluated for association with overall survival (OS). The prognostic heterogeneity features were selected using lasso/elastic net regression, and further were evaluated by multivariate Cox analysis. RESULTS Median age was 69 y (range, 46-86 y). The texture map and temporal variations between pre- and post-treatment were well characterized by histograms and statistical fitting. The lasso analysis identified seven predictors (age, node stage, post-RT SUVmax, variations of homogeneity, variance, sum mean, and cluster tendency). The multivariate Cox analysis identified five significant variables: age, node stage, variations of homogeneity, variance, and cluster tendency (with P=0.020, 0.040, 0.065, 0.078, and 0.081, respectively). The patients were stratified into two groups based on the risk score of multivariate analysis with log-rank P=0.001: a low risk group (n=11) with a longer mean OS (29.3 months) and higher texture variation (>30%), and a high risk group (n=15) with a shorter mean OS (17.7 months) and lower texture variation (<15%). CONCLUSIONS Locoregional metabolic texture response provides a feasible approach for evaluating and predicting clinical outcomes following treatment of PA with RT. The proposed method can be used to stratify patient risk and help select appropriate treatment strategies for individual patients toward implementing response-driven adaptive RT.

Stratification of Prognosis of Triple-Negative Breast Cancer Patients Using Combinatorial Biomarkers.

Background Triple-negative breast cancer (TNBC) is highly diverse group of cancers, and generally considered an aggressive disease associated with poor survival. Stratification of TNBC is highly desired for both prognosis and treatment decisions to identify patients who may benefit from less aggressive therapy. Methods This study retrieved 192 consecutive non-metastasis TNBC patients who had undergone a resection of a primary tumor from 2008 to 2012. All samples were negative for ER, PR, and HER2/neu. Disease-free-survival (DFS) and overall-survival (OS) were evaluated for expression of immunohistochemical biomarkers (P53, Ki-67, CK5/6 and EGFR), as well as clinicopathological variables including age, tumor size, grade, lymph node status, pathologic tumor and nodal stages. The cutoff values of the basal biomarkers, EGFR and CK5/6, were estimated by time-dependent ROC curves. The prognostic values of combinatorial variables were identified by univariate and multivariate Cox analysis. Patients were stratified into different risk groups based on expression status of identified prognostic variables. Results Median age was 57 years (range, 28–92 years). Patients’ tumor stage and nodal stage were significantly associated with OS and DFS. EGFR and CK5/6 were significant prognostic variables at cutoff points of 15% (p = 0.001, AUC = 0.723), and 50% (p = 0.006, AUC = 0.675), respectively. Multivariate Cox analysis identified five significant variables: EGFR (p = 0.016), CK5/6 (p = 0.018), Ki-67 (p = 0.048), tumor stage (p = 0.010), and nodal stage (p = 0.003). Patients were stratified into low basal (EGFR≤15% and CK5/6≤50%) and high basal (EGFR>15% and/or CK5/6>50%) expression groups. In the low basal expression group, patients with low expressions of Ki-67, low tumor and nodal stage had significantly better survival than those with high expressions/stages of three variables, log-rank p = 0.015 (100% vs 68% at 50 months). In the high basal expression group, patient with high basal expression of both biomarkers (EGFR >15% and CK5/6 >50%) had worse survival (mean DFS = 25 months, 41.7% event rate) than those patient with high expression of either one marker (mean DFS = 34 months, 25.5% event rate). Conclusions Immunoexpression of basal biomarkers, EGFR and CK5/6, is useful in predicting survival of TNBC patients. Integrated with Ki-67, tumor and nodal stages, combinatorial biomarker analysis provides a feasible clinical solution to stratify patient risks and help clinical decision-making with respect to selecting the appropriate therapies for individual patients.

Geometric validation of self‐gating k‐space‐sorted 4D‐MRI vs 4D‐CT using a respiratory motion phantom

PURPOSE MRI is increasingly being used for radiotherapy planning, simulation, and in-treatment-room motion monitoring. To provide more detailed temporal and spatial MR data for these tasks, we have recently developed a novel self-gated (SG) MRI technique with advantage of k-space phase sorting, high isotropic spatial resolution, and high temporal resolution. The current work describes the validation of this 4D-MRI technique using a MRI- and CT-compatible respiratory motion phantom and comparison to 4D-CT. METHODS The 4D-MRI sequence is based on a spoiled gradient echo-based 3D projection reconstruction sequence with self-gating for 4D-MRI at 3 T. Respiratory phase is resolved by using SG k-space lines as the motion surrogate. 4D-MRI images are reconstructed into ten temporal bins with spatial resolution 1.56 × 1.56 × 1.56 mm(3). A MRI-CT compatible phantom was designed to validate the performance of the 4D-MRI sequence and 4D-CT imaging. A spherical target (diameter 23 mm, volume 6.37 ml) filled with high-concentration gadolinium (Gd) gel is embedded into a plastic box (35 × 40 × 63 mm(3)) and stabilized with low-concentration Gd gel. The phantom, driven by an air pump, is able to produce human-type breathing patterns between 4 and 30 respiratory cycles/min. 4D-CT of the phantom has been acquired in cine mode, and reconstructed into ten phases with slice thickness 1.25 mm. The 4D images sets were imported into a treatment planning software for target contouring. The geometrical accuracy of the 4D MRI and CT images has been quantified using target volume, flattening, and eccentricity. The target motion was measured by tracking the centroids of the spheres in each individual phase. Motion ground-truth was obtained from input signals and real-time video recordings. RESULTS The dynamic phantom has been operated in four respiratory rate (RR) settings, 6, 10, 15, and 20/min, and was scanned with 4D-MRI and 4D-CT. 4D-CT images have target-stretching, partial-missing, and other motion artifacts in various phases, whereas the 4D-MRI images are visually free of those artifacts. Volume percentage difference for the 6.37 ml target ranged from 5.3% ± 4.3% to 10.3% ± 5.9% for 4D-CT, and 1.47 ± 0.52 to 2.12 ± 1.60 for 4D-MRI. With an increase of respiratory rate, the target volumetric and geometric deviations increase for 4D-CT images while remaining stable for the 4D-MRI images. Target motion amplitude errors at different RRs were measured with a range of 0.66-1.25 mm for 4D-CT and 0.2-0.42 mm for 4D-MRI. The results of Mann-Whitney tests indicated that 4D-MRI significantly outperforms 4D-CT in phase-based target volumetric (p = 0.027) and geometric (p < 0.001) measures. Both modalities achieve equivalent accuracy in measuring motion amplitude (p = 0.828). CONCLUSIONS The k-space self-gated 4D-MRI technique provides a robust method for accurately imaging phase-based target motion and geometry. Compared to 4D-CT, the current 4D-MRI technique demonstrates superior spatiotemporal resolution, and robust resistance to motion artifacts caused by fast target motion and irregular breathing patterns. The technique can be used extensively in abdominal targeting, motion gating, and toward implementing MRI-based adaptive radiotherapy.

TU‐F‐17A‐04: Respiratory Phase‐Resolved 3D MRI with Isotropic High Spatial Resolution: Determination of the Average Breathing Motion Pattern for Abdominal Radiotherapy Planning

PURPOSE To develop a retrospective 4D-MRI technique (respiratory phase-resolved 3D-MRI) for providing an accurate assessment of tumor motion secondary to respiration. METHODS A 3D projection reconstruction (PR) sequence with self-gating (SG) was developed for 4D-MRI on a 3.0T MRI scanner. The respiration-induced shift of the imaging target was recorded by SG signals acquired in the superior-inferior direction every 15 radial projections (i.e. temporal resolution 98 ms). A total of 73000 radial projections obtained in 8-min were retrospectively sorted into 10 time-domain evenly distributed respiratory phases based on the SG information. Ten 3D image sets were then reconstructed offline. The technique was validated on a motion phantom (gadolinium-doped water-filled box, frequency of 10 and 18 cycles/min) and humans (4 healthy and 2 patients with liver tumors). Imaging protocol included 8-min 4D-MRI followed by 1-min 2D-realtime (498 ms/frame) MRI as a reference. RESULTS The multiphase 3D image sets with isotropic high spatial resolution (1.56 mm) permits flexible image reformatting and visualization. No intra-phase motion-induced blurring was observed. Comparing to 2D-realtime, 4D-MRI yielded similar motion range (phantom: 10.46 vs. 11.27 mm; healthy subject: 25.20 vs. 17.9 mm; patient: 11.38 vs. 9.30 mm), reasonable displacement difference averaged over the 10 phases (0.74mm; 3.63mm; 1.65mm), and excellent cross-correlation (0.98; 0.96; 0.94) between the two displacement series. CONCLUSION Our preliminary study has demonstrated that the 4D-MRI technique can provide high-quality respiratory phase-resolved 3D images that feature: a) isotropic high spatial resolution, b) a fixed scan time of 8 minutes, c) an accurate estimate of average motion pattern, and d) minimal intra-phase motion artifact. This approach has the potential to become a viable alternative solution to assess the impact of breathing on tumor motion and determine appropriate treatment margins. Comparison with 4D-CT in a clinical setting is warranted to assess the value of 4D-MRI in radiotherapy planning. This work supported in part by grant 1R03CA173273-01.

TU‐F‐17A‐06: Motion Stability and Dosimetric Impact of Spirometer‐Based DIBH‐RT of Left‐Sided Breast Cancer

PURPOSE Patients undergoing radiotherapy (RT) for left-sided breast cancer have increased risk of coronary artery disease. Deep Inhalation Breath Hold assisted RT (DIBH-RT) is shown to increase the geometric separation of the target area and heart, reducing cardiac radiation dose. The purposes of this study are to use Cine MV portal images to determine the stability of spirometer-guided DIBH-RT and examine the dosimetric cardiopulmonary impact of this technique. METHODS Twenty consecutive patients with left-sided breast cancer were recruited to the IRB-approved study. Free-breathing (FB) and DIBH-CTs were acquired at simulation. Rigid registration of the FB-CT and DIBH-CT was performed using primarily breast tissue. Treatment plans were created for each FB-CT and DIBH-CT using identical paired tangent fields with field-in-field or electronic compensation techniques. Dosimetric evaluation included mean and maximum (Dmax) doses for the left anterior descending artery (LAD), mean heart dose, and left lung V20. Cine MV portal images were acquired for medial and lateral fields during treatment. Analysis of Cine images involved chest wall segmentation using an algorithm developed in-house. Intra- and inter-fractional chest wall motion were determined through affine registration to the first frame of each Cine. RESULTS Dose to each cardiac structure evaluated was significantly (p<0.001) reduced with the DIBH plans. Mean heart dose decreased from 2.9(0.9-6.6) to 1.6(0.6-5.3) Gy; mean LAD dose from 16.6(3-43.6) to 7.4(1.7-32.7) Gy; and LAD Dmax from 35.4 (6.1-53) to 18.4(2.5-51.2) Gy. No statistically significant reduction was found for the left lung V20. Average AP and SI median chest wall motion (intrafractional) was 0.1 (SD=0.9) and 0.5 (SD=1.1) mm, respectively. Average AP inter-fractional chest wall motion was 2.0 (SD=1.4) mm. CONCLUSION Spirometer-based DIBH treatments of the left breast are reproducible both inter- and intra-fractionally, and provide a statistically and potentially clinically useful dosimetric advantage to cardiac structures.

Androgen receptor positive triple negative breast cancer: Clinicopathologic, prognostic, and predictive features

Introduction Overexpression of the androgen receptor (AR) characterizes a distinct molecular subset of triple negative breast carcinomas (TNBC). The role of AR as a prognostic/predictive biomarker in TNBC is controversial, but increasing evidence suggests that this subset may respond to therapeutic agents targeting AR. Evaluation of AR has not been standardized, and criteria for selection of patients for antiandrogen therapy remain controversial. In this study we determine the appropriate threshold of AR immunoreactivity to define AR positive (AR+) TNBC, describe the clinicopathologic features of AR+ TNBC, and discuss the utility of AR positivity as a prognostic and predictive marker in TNBC. Materials and methods 135 invasive TNBC processed in accordance with ASCO/CAP guidelines, were immunostained for AR. Clinicopathologic features of AR+ TNBC were analyzed and compared to AR negative (AR-) TNBC. Patients’ age, tumor size, tumor grade, lymph node status, proliferation rate, immunopositivity for EGFR, CK5/6, Ki-67, and disease free survival (DFS) were evaluated statistically. Results A 1% cutpoint was confirmed as the appropriate threshold for AR positivity. Using this cutpoint 41% of 135 TNBC were AR+. AR+ TNBC occurred in older women, were larger, had lower mean proliferation rate and increased incidence of axillary metastasis than AR- TNBC. 76% of TNBC with apocrine morphology were AR+. A subset of AR+TNBC expressed basal markers (EGFR and CK5/6). A prognostic model was created. Summary AR identifies a heterogeneous group of TNBC. Additional evaluation of EGFR expression allowed us to stratify TNBCs into 3 risk groups with significant differences in DFS and therapeutic implications: low-risk (AR+ EGFR-) which represents the LAR molecular subtype with the best prognosis and may benefit the most from anti-androgen therapies; high-risk (AR- EGFR+) which represents the basal molecular subtype with the worst prognosis and may benefit the most from chemotherapy regimens; intermediate-risk (AR+EGFR+ and AR-EGFR-) TNBC with an intermediate prognosis. Prospective trials are required to further validate this prognostic and predictive grouping.

Comparison of endoscopic ultrasound guided fine needle aspiration and PET/CT in preoperative diagnosis of pancreatic adenocarcinoma

BACKGROUND Endoscopic ultrasound guided fine needle aspiration (EUS-FNA) is the procedure of choice to investigate and sample pancreatic masses for the preoperative diagnosis of pancreatic ductal adenocarcinoma (PDAC). The role of 18fluoro-deoxyglucose positron emission tomography/computed tomography (PET/CT) in PDAC is debated. This study evaluates the role of EUS-FNA as compared to PET/CT in the preoperative evaluation of PDAC. METHODS Preoperative evaluation by PET/CT and EUS-FNA was performed on 25 patients with pancreatic solid lesions, who underwent a subsequent Whipple procedure or partial pancreatic resection. RESULTS This series included 19 PDACs and 6 non-PDACs including 1 metastatic breast ductal adenocarcinoma, 2 low grade neuroendocrine tumors, 2 chronic pancreatitis and 1 gastrointestinal tumor abutting the pancreas. EUS-FNA correctly diagnosed 18 of 19 PDACs, 1 metastatic breast ductal adenocarcinoma and all 5 of the other non-PDAC cases. One case of well differentiated PDAC was negative on EUS-FNA. PET/CT provided excellent size and was positive in 14 of 19 PDACs and the metastatic breast ductal adenocarcinoma. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy for EUS-FNA in diagnosis of selected pancreatic tumors were 91%, 100%, 100%, 50% and 92%, respectively, while they were 65%, 100%, 100%, 20% and 68% for PET/CT, respectively. CONCLUSIONS Compared to PET/CT, EUS-FNA has a higher sensitivity and accuracy for preoperative diagnosis of PDAC. However, PET/CT provides excellent size, volume and stage information. A combination of both PET/CT and EUS will better help guide diagnosis and treatment of pancreatic adenocarcinoma.

WE-FG-BRA-11: Theranostic Platinum Nanoparticle for Radiation Sensitization in Breast Cancer Radiotherapy

PURPOSE We have developed a novel receptor-targeted theranostic platinum nanoparticle (HER-PtNP) for enhanced radiation sensitization in HER2-positive breast cancer radiation treatment. This study aims to evaluate receptor-targeting specificity, and radiation sensitization of the nanoparticle. METHODS The platinum nanoparticle (PtNP) was synthesized with the diameter of 2nm, and capped with cysteine. The nanoparticle was tagged with a fluorescent dye (cy5) for the fluoresence detection, and conjuated with HER2/3 targeted protein (HerPBK10) for HER2-targeting specificity. We evaluated the theranostic features using in vitro breast cancer cell models: HER2-positive BT-474, and HER2-negative MDA-MB-231. The HER2-targeting specificity was evaluated using immunofluorescence and confocal microscopy. For each cell line, three sets of samples, including non-stained control, fluorescence stained PtNP-cy5 treated, and HER-PtNP treated, were imaged by confocal microscopy. Two breast cancer cell lineages were incubated with PtNP and HER-PtNP at 10 µg/mL, and then irradiated with X-rays for 2 Gy dose at 50 kVp. A colonogenic assay was used to determine cellular survival fractions by immediately reseeding 300 cells after irradiation in growth media and allowing colonies to grow for 2 weeks. RESULTS The results of confocal images show that no apparent nanoparticle cellular uptake was observed in the HER2-(MDA-MB-231) cells with 1% for PtNP-cy5 and 0.5% for HER-PtNP. Similarly no apparent PtNP-cy5 uptake (<1%) for BT474 cells was observed. However, there was significant HER-PtNP uptake (73%) for the HER2+(BT474) cells. The clonogenic assay showed that BT474 cells treated with HER-PtNP had significantly lower survival compared to those treated with PtNP (32% vs 81%, p=0.01). However, no significant radiosensitivity enhancement was observed for MDA-MB-231 cell treated with PtNP and HER-PtNP (89% vs 92%, p=0.78). CONCLUSION Our studies suggest that the HER2-targeted platinum nanoparticle has excellent receptor targeting specificity and enhanced radiation sensitization compared to nanoparticle alone, suggesting potential for clinical applications in breast cancer radiotherapy.

Abstract P5-01-03: Stratifying triple-negative breast cancer prognosis using 18F-FDG-PET/CT imaging

Introduction: Triple-negative breast cancer (TNBC) is a highly diverse group of cancers, and may benefit from molecular-targeted therapies. This study aims to stratify prognosis of TNBC patients using pre-treatment 18F-FDG PET/CT, alone and with correlation to immunohistochemistry biomarkers. Method: 200 consecutive TNBC breast cancer patients treated between 2008 and 2012 who received lumpectomy or mastectomy as primary treatment were retrieved. Among the full cohort, 79 patients had pre-treatment 18F FDG PET/CT scans. Immunostaining status (percentage and intensity) of basal biomarkers (EGFR, CK5/6), Ki-67, P53, and other clinicopathological variables (age, tumor size, pathological T/N stage, nuclear grade, and lymph node metastasis) were obtained. Three PET image features were evaluated: maximum uptake values (SUVmax), mean uptake (SUVmean) and target volume (SUVvol) defined by SUV>2.5. The relationships among tumor metabolic activities and clinicopathological factors were evaluated. All variables were analyzed versus disease-free survival (DFS) using univariate and multivariate Cox analysis, Kaplan-Meier curves and log-rank tests. The optimal cutoff points of variables were estimated using time-dependent survival receiver operating characteristic (ROC) analysis. Results: All PET features significantly correlated with proliferation marker Ki-67 (all p 3.5, AUC=0.654, p=0.006). Basal biomarkers EGFR and CK5/6 and image features SUVmax, SUVmean, SUVvol were significant associated with DFS in univariate Cox analysis, whereas SUVmax (p=0.001) and EGFR (p=0.001) were also significant in multivariate Cox analysis. To integrate prognosis of biological and imaging markers, patients were first stratified by EGFR into low (≤15%) and high (>15%) risk groups. Further, SUVmax was used as a variable to stratify the two EGFR groups. In the high EGFR group, patients with high FDG uptake (SUVmax>3.5) had worse survival outcome (median DFS=7.6 months) than those patients with low FDG uptake (SUVmax≤3.5, median DFS=11.6 months). In the low EGFR group, high SUVmax also indicated worse survival outcome (17.2 months) than low SUVmax (22.8 months). The risk stratification with integrative EGFR and PET was statistically significant with log-rank p Conclusions: Pre-treatment 18F-FDG PET/CT imaging has significant prognostic value for predicting survival outcome of TNBC patients. Integrated with basal-biomarker EGFR, PET imaging can further stratify patient risks in the pre-treatment stage, and help select appropriate treatment strategies for individual patients. Citation Format: Yue Y, Cui X, Bose S, Audeh W, Zhang X, Fraass B. Stratifying triple-negative breast cancer prognosis using 18F-FDG-PET/CT imaging. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-01-03.