Introduction: Intraoperative Prostate-Specific Membrane Antigen (PSMA)-targeted radioguidance was proven to be valuable for the detection of PCa lesions during open salvage surgery. Rapid extension of robot-assisted, minimally invasive surgery has increased the need to make PSMA-radioguided surgery (RGS) robot compliant. Here we aim to evaluate whether the miniaturized DROP-IN gamma probe facilitates translation of PSMA-targeted radioguidance to salvage robotic surgery in men with recurrent PCa.
Methods: This prospective feasibility study (NCT03857113) included twenty patients with a biochemical recurrence (PSA = 0.2 ng/ml) after radical prostatectomy or radiotherapy with up to 2 pelvic PCa recurrences (either nodal or local) on PSMA positron emission tomography (PET)/CT. Patients received an intravenous injection of 99mTc-PSMA I&S (median activity 541 MBq, IQR 526-578) followed by scintigraphy as a control for tracer injection and distribution. Robot-assisted PSMA-RGS was realized using the tethered gamma probe 19-23 hours post-injection. The primary endpoint was the feasibility of PSMA-RGS in a robotic setting. Secondary endpoints were the comparison of the radioactive status (i.e., positive or negative) of the resected specimens and final histopathology results, the frequency of >50% prostate-specific antigen (PSA) reduction, complete biochemical response (cBR; PSA <0.2 ng/ml) 6 weeks postoperatively, and complications according to Clavien-Dindo 30 days postoperatively.
Results: At surgery, the median age was 68 years (IQR 66-72) and median PSA was 1.02 ng/ml (IQR 0.46-2.43). Using the DROP-IN probe, 19 out of 21 (90%) PSMA PET-avid lesions could be resected robotically with a median surgical duration of 128 min (IQR 103-157). On a per-lesion basis, the overall diagnostic sensitivity and specificity of robot-assisted PSMA-RGS was 86% and 100%, respectively. A >50% PSA reduction and cBR was seen in 12 out of 18 (67%) and 3 out of 18 (17%) patients, respectively. No Clavien-Dindo grade =2 complications occurred.
Conclusions: The DROP-IN probe helps to realize robot-assisted PSMA-RGS. The procedure is technically feasible for the intraoperative detection of nodal or local PSMA-avid PCa recurrences.
Source of Funding: Partly supported by an NWO-TTW-VICI grant (TTW 16141)