Robot-Assisted PSMA-Radioguided Salvage Surgery for Oligorecurrent Prostate Cancer Using the Novel SENSEI® Drop-in Gamma Probe: Correlation of Intraoperative Measurements to Preoperative Imaging and Final Histology

Background: To examine the feasibility and safety of the SENSEI (R) drop-in gamma probe for robot-assisted, prostate-specific membrane antigen (PSMA)-radioguided salvage surgery (RGS) in lymph node or local oligorecurrent prostate cancer (PCa), detected via PSMA positron emission tomography/computed tomography (PET/CT). Methods: The first thirteen patients with pelvic oligorecurrent PCa who underwent [99mTc]Tc-PSMA-I&S RGS using the SENSEI (R) drop-in gamma probe at the Martini-Klinik (February-June 2024) were retrospectively analyzed. Radioactivity measurements in counts per second (CPS) as absolute values or ratios (CPS of tumor specimens/mean CPS from the patients' benign tissues) were correlated with preoperative imaging and pathological findings (benign/malignant, lesion size). Postoperative complete biochemical response (cBR) was defined as prostate-specific antigen (PSA) levels of <0.2 ng/mL. Results: Fifty-four specimens were removed from 13 patients, with nineteen (35%) containing PCa. All patients had one PSMA PET/CT-positive lesion, which were all detected intraoperatively. These lesions showed higher ex vivo CPS, CPS ratios, and larger cancer diameters than PSMA PET/CT-negative lesions (all p < 0.05). Cancer-containing specimens exhibited higher CPS and CPS ratios than benign tissues (median values of 45 vs. 3, and 9.9 vs. 1.0, both p < 0.001). In total, 12/13 (92%) patients achieved cBR. Conclusions: This device yielded excellent detection rates with good correlation to preoperative imaging and histological results without adverse events.