Comparison of PET/CT and whole-mount histopathology sections of the human prostate: a new strategy for voxel-wise evaluation.

BACKGROUND: Implementation of PET/CT in diagnosis of primary prostate cancer (PCa) requires a profound knowledge about the tracer, preferably from a quantitative evaluation. Direct visual comparison of PET/CT slices to whole prostate sections is hampered by considerable uncertainties from imperfect coregistration and fundamentally different image modalities. In the current study, we present a novel method for advanced voxel-wise comparison of histopathology from excised prostates to pre-surgical PET. Resected prostates from eight patients who underwent PSMA-PET/CT were scanned (ex vivo CT) and thoroughly pathologically prepared. In vivo and ex vivo CT including histopathology were coregistered with three different methods (manual, semi-/automatic). Spatial overlap after CT-based registration was evaluated with dice similarity (DSC). Furthermore, we constructed 3D cancer distribution models from histopathologic information in various slices. Subsequent smoothing reflected the intrinsically limited spatial resolution of PSMA-PET. The resulting histoPET models were used for quantitative analysis of spatial histopathology-PET pattern agreement focusing on p values and coefficients of determination (R 2). We examined additional rigid mutual information (MI) coregistration directly based on PSMA-PET and histoPET. RESULTS: Mean DSC for the three different methods (ManReg, ScalFactReg, and DefReg) were 0.79 ± 0.06, 0.82 ± 0.04, and 0.90 ± 0.02, respectively, while quantification of PET-histopathology pattern agreement after CT-based registration revealed R 2 45.7, 43.2, and 41.3% on average with p < 10-5. Subsequent PET-based MI coregistration yielded R 2 61.3, 55.9, and 55.6%, respectively, while implying anatomically plausible transformations. CONCLUSIONS: Creating 3D histoPET models based on thorough histopathological preparation allowed sophisticated quantitative analyses showing highly significant correlations between histopathology and (PSMA-)PET. We recommend manual CT-based coregistration followed by a PET-based MI algorithm to overcome limitations of purely CT-based coregistrations for meaningful voxel-wise comparisons between PET and histopathology.

Quantitative proteomic analysis of formalin-fixed, paraffin-embedded clear cell renal cell carcinoma tissue using stable isotopic dimethylation of primary amines.

BACKGROUND: Formalin-fixed, paraffin-embedded (FFPE) tissues represent the most abundant resource of archived human specimens in pathology. Such tissue specimens are emerging as a highly valuable resource for translational proteomic studies. In quantitative proteomic analysis, reductive di-methylation of primary amines using stable isotopic formaldehyde variants is increasingly used due to its robustness and cost-effectiveness. RESULTS: In the present study we show for the first time that isotopic amine dimethylation can be used in a straightforward manner for the quantitative proteomic analysis of FFPE specimens without interference from formalin employed in the FFPE process. Isotopic amine dimethylation of FFPE specimens showed equal labeling efficiency as for cryopreserved specimens. For both FFPE and cryopreserved specimens, differential labeling of identical samples yielded highly similar ratio distributions within the expected range for dimethyl labeling. In an initial application, we profiled proteome changes in clear cell renal cell carcinoma (ccRCC) FFPE tissue specimens compared to adjacent non-malignant renal tissue. Our findings highlight increased levels of glyocolytic enzymes, annexins as well as ribosomal and proteasomal proteins. CONCLUSION: Our study establishes isotopic amine dimethylation as a versatile tool for quantitative proteomic analysis of FFPE specimens and underlines proteome alterations in ccRCC.

Salvage lymph node dissection with adjuvant radiotherapy for nodal recurrence of prostate cancer.

PURPOSE: We evaluated the impact of salvage lymph node dissection with adjuvant radiotherapy in patients with nodal recurrence of prostate cancer. By default, nodal recurrence of prostate cancer is treated with palliative antihormonal therapy, which causes serious side effects and invariably leads to the development of hormone refractory disease. MATERIALS AND METHODS: A total of 47 patients with nodal recurrence of prostate cancer based on evidence of (11)C-choline/(18)F-choline ((18)F-fluorethylcholine) positron emission tomography-computerized tomography underwent primary (2 of 52), secondary (45 of 52), tertiary (4 of 52) and quaternary (1 of 52) salvage lymph node dissection with histological confirmation. Of 52 salvage lymph node dissections 27 were followed by radiotherapy. Biochemical response was defined as a prostate specific antigen less than 0.2 ng/ml after salvage therapy. The Kaplan-Meier method, binary logistic regression and Cox regression were used to analyze survival as well as predictors of biochemical response and clinical progression. RESULTS: Mean prostate specific antigen at salvage lymph node dissection was 11.1 ng/ml. A mean of 23.3 lymph nodes were removed per salvage lymph node dissection. Median followup was 35.5 months. Of 52 salvage lymph node dissections 24 resulted in complete biochemical response followed by 1-year biochemical recurrence-free survival of 71.8%. Gleason 6 or less (OR 7.58, p = 0.026), Gleason 7a/b (OR 5.91, p = 0.042) and N0 status at primary therapy (OR 8.01, p = 0.011) were identified as independent predictors of biochemical response. Gleason 8-10 (HR 3.5, p = 0.039) as a preoperative variable, retroperitoneal positive lymph nodes (HR 3.76, p = 0.021) and incomplete biochemical response (HR 4.0, p = 0.031) were identified as postoperative predictors of clinical progression. Clinical progression-free survival was 25.6% and cancer specific survival was 77.7% at 5 years. CONCLUSIONS: Based on (11)C/(18)F-choline positron emission tomography-computerized tomography as a diagnostic tool, salvage lymph node dissection is feasible for the treatment of nodal recurrence of prostate cancer. Most patients experience biochemical recurrence after salvage lymph node dissection. However, a specific population has a lasting complete prostate specific antigen response.