8: PSMA-expression in renal cell carcinoma as basis for theranostic approaches – an immunohistochemical nephrectomy study
Location: Poster Hall, Board B2
Stephan Ledderose, MD; Severin Rodler, MD; Matthias Brendel, MD; Peter Bartenstein, MD; Frederick Klauschen, MD; Marcus Unterrainer, MD; Michael Staehler, MD; Vinh Ngoc Bui
Background: PSMA, the prostate-specific membrane antigen, represents a target for imaging and radionuclide therapy in metastatic prostate cancer patients. PSMA is also known to be expressed on the tumor-associated neovascularization of renal cell carcinoma (RCC). Pilot studies could already demonstrate the potential use of PSMA PET/CT as response assessment tool for metastatic RCC (mRCC). However, PSMA-expression in PET imaging of RCC is heterogenous. We hypothesized that histological RCC subtypes might be associated with differences in PSMA-expression as basis for further pathology based theranostic approaches.
Methods: We assessed the influence of histological RCC subtypes on PSMA-expression by immunhistochemistry. Formalin-fixed and paraffin-embedded material from nephrectomy specimens of RCC patients were immunohistochemically examined using antibody 3E6 against PSMA. Intensity of staining and extent were evaluated semi-quantitatively and correlated with the histological RCC subtypes (clear cell RCC (ccRCC), papillary RCC (pRCC) and chromophobe RCC (cpRCC)).
Results: 62 nephrectomy cases were included. 22/62 (35.5%) cases comprised pRCC, 21/62 (33.9%) ccRCC and 19/62 (30.6%) cpRCC. In all these cases, immunoreactivity was detected only in the tumor-associated vessels. Staining intensity was the strongest in ccRCC followed by cpRCC and pRCC (mean 2.67 vs. 1.75 vs. 1.09) (p < 0.001); ccRCC showed the most diffuse staining pattern, where 18/21 (85.7%) ccRCC cases had a diffuse staining (> 50% reactive tumorvessels), followed by cpRCC and pRCC.
Conclusions: We could demonstrate that ccRCC shows the highest level of PSMA expression followed by cpRCC while the pRCC subtype exhibited barely any PSMA-expression. These differences in PSMA-expression could lead to a selection for theranostic approaches in mRCC patients.