Value of ¹¹¹ In-prostate-specific membrane antigen (PSMA)-radioguided surgery for salvage lymphadenectomy in recurrent prostate cancer: correlation with histopathology and clinical follow-up.

Abstract

To evaluate the use of ¹¹¹ In-labelled prostate-specific membrane antigen (PSMA)-I&T-based radioguided surgery (¹¹¹ In-PSMA-RGS) for salvage surgery in recurrent prostate cancer (PCa) using comparison of intra-operative gamma probe measurements with histopathological results of dissected specimens. In addition, to determine the success of ¹¹¹ In-PSMA-RGS with regard to postoperative prostate-specific antigen (PSA) responses, PCa-specific treatment-free survival rates and postoperative complication rates. A total of 31 consecutive patients with localized recurrent PCa undergoing salvage surgery with PSMA-targeted radioguided surgery using a ¹¹¹ In-labelled PSMA ligand between April 2014 and July 2015 were retrospectively included in this study. The preoperative (interquartile range; range) median PSA level was 1.3 (0.57-2.53 ng/mL; 0.2-13.9 ng/mL). Results of ex vivo radioactivity rating (positive vs negative) of resected tissue specimens were compared with findings of postoperative histological analysis. Best PSA response without additional treatment was determined after ¹¹¹ In-PSMA-RGS, and salvage-surgery-related postoperative complications and PCa-specific additional treatments were recorded. In 30/31 patients, ¹¹¹ In-PSMA-RGS allowed intra-operative identification of metastatic lesions. In total, 145 surgical specimens were removed and 51 showed metastatic involvement at histological analysis. According to ¹¹¹ In-PSMA-RGS ex vivo measurements, 48 specimens were correctly classified as metastatic and 87 as cancer-free, four were false-negative and six were false-positive compared with histological evaluation. Follow-up information was available for 30/31 patients. PSA declines of >50% and >90% were observed in 23/30 patients and in 16/30 patients, respectively. In 18/30 patients, a PSA decline to <0.2 ng/mL was observed. In 10/30 patients further PCa-specific treatment was given after a median (range) of 125 (48-454) days post-¹¹¹ In-PSMA-RGS. The remaining 20 patients remained treatment-free at a median (range) follow-up of 337 (81-591) days. Of 30 patients, 10 presented with surgery-related complications (Clavien-Dindo grade 1, n = 6, Clavien-Dindo grade 3b, n = 4). ¹¹¹ In-PSMA-RGS proved to be of high value for intra-operative detection of even small metastatic lesions in patients with PCa scheduled for salvage lymphadenectomy. It allows the exact localization and resection of metastatic tissue during ¹¹¹ In-PSMA-RGS and is therefore anticipated to have a beneficial influence on further disease progression; however, identification of suitable patients on the basis of PSMA-positron-emission tomography imaging as well as clinical variables is essential for satisfactory results to be obtained.