A PSMA-targeted theranostic approach is unlikely to be efficient in serous ovarian cancers

Purpose Until now, results evaluating the expression of PSMA in ovarian cancer were sparse and contradictory. The aim was to reinvestigate the feasibility of a PSMA targeted theranostic approach in epithelial ovarian cancers with data from the tumour bank of a referring cancer centre. Materials and methods The OvaRessources Biological Resources Center database was screened from January 2004 to December 2017 to seek patients referred for the initial management of a serous epithelial ovarian cancer and for whom peritoneal histological samples were available in the tumour bank. Immunodetection of PSMA was performed to assess its cellular and neovascular expression. Slides were controlled by a certified pathologist, recorded as tiled tiff images and processed to compute the proportion of DAB stained surface. Results Of the 51 patients identified by the database screening, 32 patients were included resulting in 57 samples (32 pre-chemotherapy and 25 post-chemotherapy histological samples). Nine patients were chemo-sensitive, 10 were partially chemo-sensitive and 13 were chemo-resistant/refractory. In the entire dataset, the expression of PSMA was quasi-inexistent: %DAB PSMA = 0.04 (± 0.12) %. There was no significant difference in the %DAB PSMA of sensitive, partially sensitive and resistant/refractory patients. There was also no significant difference in %DAB PSMA in tumours before and after chemotherapy in the 25 patients for whom both samples were available. Conclusion The present work demonstrates that PSMA expression is negligible and a fortiori non-sufficient to ensure its usefulness as a prognosticator or a target for a theranostic strategy in ovarian cancers.