PD22-05: Is pre operative PSMA (Prostate Specific Membrane Antigen) PET/CT a reliable predictor of pelvic lymph node metastasis in intermediate and high risk localised prostate cancer:A multi centre retrospective analysis
Introduction: Functional imaging techniques have been incorporated into conventional anatomical imaging to help improve identification of metastasis in normal sized nodes The primary objective of this study was to retrospectively analyse the percentage of patients “negative for metastasis” on 68Ga PSMA PETCT that translated to absent pelvic node metastasis on histopathology (Negative predictive value-NPV). The secondary objective was to analyse if pathological T stage and biopsy ISUP grades influenced the NPV of the PSMA PET CT. Methods: A total of 217 biopsy-proven, treatment-naive, intermediate and high-risk (D’Amico classification) localised prostate cancer patients from two institutions were included in the study. All the patients had undergone a pre operative PSMA PET/ CT assessment of their pelvic lymph nodes and the patients “negative for metastasis” underwent Robotic assisted radical prostatectomy with extended pelvic lymph node dissection-ePLND. Results: 49/217 patients had positive nodes despite PSMA PET/CT showing no evidence of lymph node metastasis,of which 27(55.10%) of them were obese. Thus the negative predictive value(NPV) was 77.42%. The NPV of PSMA PET CT in patients with intermediate risk prostate cancer was 86.9% compared to 71.43% in patients with high risk prostate cancer. As the ISUP biopsy grade increased the NPV decreased from 94.12% in ISUP 1 to 44.83%(p < 0.0001) in ISUP 5.On retrospective analysis, all intermediate risk patients with a Conclusions: PSMA PET CT cannot replace e PLND with respect to accurate preoperative lymph nodal staging in intermediate and high risk prostate cancer since the NPV is below 95% (86.9%,71.43% respectively. PSMA PET CT is also not accurate with the T staging because pre operative T2 was upstaged to pT3 in 66.6 % of intermediate risk and 81.9% of high risk patients.Thus preoperative PSMA PET CT is not reliable for accurate T and N staging and e PLND should be the standard of care for precise staging in intermediate and high risk localized prostate cancer. SOURCE OF Funding: Self funded study
