Salvage lymph node dissection for prostate-specific membrane antigen (PSMA) positron emission tomography (PET)-identified oligometastatic disease

Abstract

Introduction: The availability of prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) imaging, particularly in the setting of rising prostate-specific antigen (PSA) after definitive treatment, has led to oligometastatic prostate cancer being increasingly identified. Despite the enthusiasm surrounding treating oligometastatic disease, it has been relatively understudied. We sought to review our salvage lymphadenectomy experience in the PSMA PET/CT era. Methods: We retrospectively reviewed patients undergoing lymphadenectomy following curative intent primary therapy with rising PSA who had undergone a PSMA PET/CT identifying oligometastatic disease (defined as 5 PSMA-avid lesions) between January 2016 to April 2020. The primary endpoint was complete response, defined as achieving a PSA <0.2 ng/ml without concomitant androgen deprivation therapy (ADT). Results: Twenty-two patients were included. Primary curative therapy included radical prostatectomy (86.4%) and brachytherapy (13.6%). Median PSA at salvage surgery was 1.72 ng/ml. Pelvic lymph node dissection was the most performed procedure (72.7%). Median node yield was 10.5, with a median of 1.5 positive nodes on pathology. Eight patients (36.4%) achieved PSA <0.2, with six (27.3%) remaining with PSA <0.2 after a median followup of 23.1 months. Nine (40.9%) had an initial PSA decline, but nadired ≥0.2, and in five (22.7%) the PSA rose immediately after surgery. Overall, ADT was commenced in seven patients (31.8%) at a median of 10.1 months post-salvage surgery. Conclusions: In our series of salvage dissection for PSMA-PET-detected nodal oligometastases, approximately a third achieved PSA <0.2; yet, it was only durable in 27%. Prospective trials of salvage nodal radiation are ongoing; however, more prospective trials of salvage node dissection are needed.