MP48-14: When Node-Positive Prostate Cancer Should Be Considered A Systemic Disease? Assessing The Prognostic Role Of Preoperative 68Ga-PSMA PET/CT Results In Patients With Lymph Node Invasion At Final Pathology

Daniele Robesti*, Elio Mazzone, Milano, Italy, Giorgio Gandaglia, Armando Stabile, Milan, Italy, Carlo Andrea Bravi, Andrea Necchi, Daniele Raggi, Laura Marandino, Milano, Italy, Giuseppe Cirulli, Milan, Italy, Francesco Barletta, Simone Scuderi, Riccardo Leni, Milano, Italy, Mario de Angelis, Vito Cucchiara, Milan, Italy, Eleonora Balestrazzi, Stefano Fanti, Andrea Farolfi, Lorenzo Bianchi, Riccardo Schiavina, Bologna, Italy, Francesco Montorsi, Alberto Briganti, Milano, Italy

Introduction: 68-Ga PSMA PET might identify nodal metastases in prostate cancer (PCa) patients considered for radical prostatectomy (RP). To date, no data addressed the prognostic value of PSMA PET/CT according to the results of lymph node dissection. Based on this unmet need, we tested the impact of a positive or negative PSMA PET/CT in patients with lymph node metastases at final pathology in order to select patients more likely to benefit from early multi-modal approaches.

Methods: We identified 92 patients evaluated with 68Ga-PSMA PET/CT before RP and extended lymph node dissection (LND) between 2019 and 2021 at two centers. The study outcome was PSA persistence, defined as first PSA value after surgery = 0.1 ng/ml. Rates of true and false positive of PSMA PET/CT in detecting positive nodes at final pathology were assessed. Descriptive characteristics compared rates of PSA persistence in patients with or without lymph nodal metastases according to preoperative PSMA PET results. The association between the preoperative PSMA PET/CT result and nodal status at final pathology on the risk of PSA persistence was investigated using logistic regression.

Results: Median PSA was 9 ng/ml (IQR: 5-16 ng/ml). Overall, 30 (33%) patients had positive spots at preoperative scan, 19 (21%) had a positive scan, while 13 (14%) had negative scan but positive nodes at pathology. Overall, 30 patients (33%) had PSA persistence. Among men with negative PSMA PET and negative nodes at pathology, 8 (17%) had PSA persistence. Among patients with positive nodes at pathology, 5 out of 13 (38%) with negative PSMA PET and 12 of the 19 patients (63%) with positive scan had PSA persistence (p=0.01). At logistic regression, men with positive nodes but negative PET PSMA had no higher risk of PSA persistence (OR 2.5, p=0.1) compared to these with negative scan and negative nodes. On the contrary, patients with positive scan and positive nodes at final pathology had substantially higher risk of PSA persistence after surgery (OR 3.93, p=0.036).

Conclusions: 68Ga-PSMA PET/CT has important prognostic implications for patients treated with RP and LND. In patients with concomitant positive PSMA PET and lymph nodal invasion, we found a 4-fold higher risk of PSA persistence when compared to patients with negative PSMA and negative nodes at pathology. Thus, patients with positive PSMA and positive nodes should be considered affected by disseminated disease and candidate for upfront multimodal treatments.

Source of Funding: None