Purpose: The exact detection and delineation of the intraprostatic tumour burden is crucial for treatment planning in primary prostate cancer (PCa). We compared 68 Ga-HBED-CC-PSMA PET/CT with multiparametric MRI (mpMRI) for diagnosis and tumour delineation in patients with primary PCa based on slice by slice correlation with histopathological reference material. Methodology: Seven patients with histopathologically proven primary PCa underwent 68 Ga-HBED-CC-PSMA PET/CT and MRI followed by radical prostatectomy. Resected prostates were scanned by ex-vivo CT in a special localizer and prepared for histopathology. Invasive PCa was delineated on a HE stained histologic tissue slide and matched to ex-vivo CT to obtain gross tumor volume (GTV-)histo. Ex-vivo CT including GTV-histo and MRI data were matched to in-vivo CT(PET). Consensus contours based on MRI (GTV-MRI), PSMA PET (GTV-PET) or the combination of both (GTV-union/-intersection) were created. In each in-vivo CT slice the prostate was separated into 4 equal segments and sensitivity and specificity for PSMA PET and mpMRI were assessed by comparison with histological reference material. Furthermore, the spatial overlap between GTV-histo and GTV-PET/-MRI and the Sørensen-Dice coefficient (DSC) were calculated. In the case of multifocal PCa (4/7 patients), SUV values (PSMA PET) and ADC-values (diffusion weighted MRI) were obtained for each lesion. Results: PSMA PET and mpMRI detected PCa in all patients. GTV-histo was detected in 225 of 340 segments (66.2%). Sensitivity and specificity for GTV-PET, GTV-MRI, GTV-union and GTV-intersection were 75% and 87%, 70% and 82%, 82% and 67%, 55% and 99%, respectively. GTV-histo had on average the highest overlap with GTV-union (57±22%), which was significantly higher than overlap with GTV-MRI (p=0.016) and GTV-PET (p=0.016), respectively. The mean DSC for GTV-union, GTV-PET and GTV-MRI was 0.51 (±0.18), 0.45 (±0.17) and 0.48 (±0.19), Ivyspring International PublisherTheranostics 2017, Vol. 7, Issue 1 http://www.thno.org 229 respectively. In every patient with multifocal PCa there was one lesion which had both the highest SUV and the lowest ADC-value (mean and max). Conclusion: In a slice by slice analysis with histopathology, 68 Ga-HBED-CC-PSMA PET/CT and mpMRI showed high sensitivity and specificity in detection of primary PCa. A combination of both methods performed even better in terms of sensitivity (GTV-union) and specificity (GTV-intersection). A moderate to good spatial overlap with GTV-histo was observed for PSMA PET/CT and mpMRI alone which was significantly improved by GTV-union. Further studies are warranted to analyse the impact of these preliminary findings for diagnostic (multimodal guided TRUS biopsy) and therapeutic (focal therapy) strategies in primary PCa.

Introduction: The gastrin-releasing peptide receptor (GRPR) is overexpressed in breast cancer. The present study evaluates GRPR imaging as a novel imaging modality in breast cancer by employing positron emission tomography (PET) and the GRPR antagonist 68Ga-RM2.Methods: Fifteen female patients with biopsy confirmed primary breast carcinoma (3 bilateral tumors; median clinical stage IIB) underwent 68Ga-RM2-PET/CT for pretreatment staging. In vivo tumor uptake of 68Ga-RM2 was correlated with estrogen (ER) and progesterone (PR) receptor expression, HER2/neu status and MIB-1 proliferation index in breast core biopsy specimens.Results: 13/18 tumors demonstrated strongly increased 68Ga-RM2 uptake compared to normal breast tissue (defined as PET-positive). All PET-positive primary tumors were ER- and PR-positive (13/13) in contrast to only 1/5 PET-negative tumors. Mean SUVMAX of ER-positive tumors was 10.6±6.0 compared to 2.3±1.0 in ER-negative tumors (p=0.016). In a multivariate analysis including ER, PR, HER2/neu and MIB-1, only ER expression predicted 68Ga-RM2 uptake (model: r2=0.55, p=0.025). Normal breast tissue showed inter- and intraindividually variable, moderate GRPR binding (SUVMAX 2.3±1.0), while physiological uptake of other organs was considerably less except pancreas. Of note, 68Ga-RM2-PET/CT detected internal mammary lymph nodes with high 68Ga-RM2 uptake (n=8), a contralateral axillary lymph node metastasis (verified by biopsy) and bone metastases (n=1; not detected by bone scan and CT).Conclusion: Our study demonstrates that 68Ga-RM2-PET/CT is a promising imaging method in ER-positive breast cancer. In vivo GRPR binding assessed by 68Ga-RM2-PET/CT correlated with ER expression in primary tumors of untreated patients.

Background: By targeting the prostate-specific membrane antigen (PSMA) on prostate cancer (PCa) cells PSMA-PET/CT shows great potential in locating the site of biochemical recurrence even at low PSA (Prostate-specific antigen)-levels. Accurate imaging of PCa recurrent lymph node metastases (LNM) is crucial for metastases directed therapies such as salvage-lymph node dissection (salvage-LND).Objective: To evaluate the diagnostic accuracy of PSMA-PET/CT for detection of affected lymph-node regions at salvage-LND for nodal recurrence of PCa.Design, setting and participants: 30 patients with the suspicion of exclusively nodal PCa-relapse after primary therapy underwent a template pelvic and/or retroperitoneal salvage-LND after whole body 68-Ga-PSMA-PET/CT. The diagnostic accuracy of PET/CT was evaluated in comparison to the histopathology of 965 resected lymph nodes (LN) dissected from 68 main regions (pelvic left/right, retroperitoneal) and 289 subregions (common iliac, external iliac, obturator, internal iliac, presacral, aortic-bifurcation, aortal, caval). LNM and tumor deposits in LNM were measured bidimensionally in the histopathology. PSMA-expression was analyzed by immunohistochemistry in LNM.Results: LNM were present in 11.4% of the resected LN (110/965) resulting in 45 positive main regions and 85 positive subregions. PET/CT was true positive in 41 main regions and 69 subregions. Three PET-negative main regions and 16 PET-negative subregions finally contained LNM, the majority of these false negative subregions (13/16) were in neighboring regions of true-positive subregions. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were: main region-based 93.2%, 100%, 100%, 88.9% and 95.6%, subregion-based 81.2%, 99.5%, 98.6%, 92.7 and 94.1%. Median short diameters of tumor deposits in LNM resected from false-negative subregions (1.3 mm) were significantly smaller than in LNM removed from true-positive subregions (5.5 mm, p<0.0001). Based on anatomical subregions containing just one LNM, the necessary short diameter of tumor deposits in LNM required to reach a detection rate of 50% and 90% was estimated to be ≥ 2.3 mm and ≥ 4.5 mm, respectively.Conclusion: In men with biochemical PCa-relapse and positive PSMA-PET/CT, PET/CT detects metastatic affected anatomical regions with high accuracy at a main region and at a subregion-level. If the decision for salvage-LND is prompted by a positive PSMA-PET/CT, the size of metastases is crucial for accurate detection of affected regions. All LNM showed a clear PSMA-expression in the immunohistochemistry. Further studies need to investigate how to translate the high anatomical correlation observed between PET/CT and surgical findings into optimal approaches for target salvage-LND.

Purpose: We performed a voxel-wise comparison of 68Ga-HBED-CC-PSMA PET/CT with prostate histopathology to evaluate the performance of 68Ga-HBED-CC-PSMA for the detection and delineation of primary prostate cancer (PCa).Methodology: Nine patients with histopathological proven primary PCa underwent 68Ga-HBED-CC-PSMA PET/CT followed by radical prostatectomy. Resected prostates were scanned by ex-vivo CT in a special localizer and histopathologically prepared. Histopathological information was matched to ex-vivo CT. PCa volume (PCa-histo) and non-PCa tissue in the prostate (NPCa-histo) were processed to obtain a PCa-model, which was adjusted to PET-resolution (histo-PET). Each histo-PET was coregistered to in-vivo PSMA-PET/CT data.Results: Analysis of spatial overlap between histo-PET and PSMA PET revealed highly significant correlations (p < 10-5) in nine patients and moderate to high coefficients of determination (R²) from 42 to 82 % with an average of 60 ± 14 % in eight patients (in one patient R2 = 7 %). Mean SUVmean in PCa-histo and NPCa-histo was 5.6 ± 6.1 and 3.3 ± 2.5 (p = 0.012). Voxel-wise receiver-operating characteristic (ROC) analyses comparing the prediction by PSMA-PET with the non-smoothed tumor distribution from histopathology yielded an average area under the curve of 0.83 ± 0.12. Absolute and relative SUV (normalized to SUVmax) thresholds for achieving at least 90 % sensitivity were 3.19 ± 3.35 and 0.28 ± 0.09, respectively.Conclusions: Voxel-wise analyses revealed good correlations of 68Ga-HBED-CC-PSMA PET/CT and histopathology in eight out of nine patients. Thus, PSMA-PET allows a reliable detection and delineation of PCa as basis for PET-guided focal therapies.