Abstract
Introduction68Ga-PSMA PET/CT is associated with unprecedented sensitivity for localization of biochemically recurrent prostate cancer at low PSA levels prior to radiotherapy. Aim of the present analysis is to examine whether patients undergoing postoperative, salvage radiotherapy (sRT) of the prostatic fossa with no known nodal or distant metastases on conventional imaging (CT and/or MRI) and on positron emission tomography/computed tomography (68Ga-PSMA PET/CT) will have an improved biochemical recurrence-free survival (BRFS) compared to patients with no known nodal or distant metastases on conventional imaging only.Material and MethodsThis retrospective analysis is based on 459 patients (95 with and 364 without 68Ga-PSMA PET/CT). BRFS (PSA < post-sRT Nadir + 0.2 ng/ml) was the primary study endpoint. This was first analysed by Kaplan-Meier and uni- and multivariate Cox regression analysis for the entire cohort and then again after matched-pair analysis using tumor stage, Gleason score, PSA at time of sRT and radiation dose as matching parameters.ResultsMedian follow-up was 77.5 months for patients without and 33 months for patients with 68Ga-PSMA PET/CT. For the entire cohort, tumor stage (pT2 vs. pT3-4; p= <0.001), Gleason score (GS ≤ 7 vs. GS8-10; p=0.003), pre-sRT PSA (<0.5 vs. ≥0.5ng/ml; p<0.001) and sRT dose (<70 vs. ≥70Gy; p<0.001) were the only factors significantly associated with improved BRFS. This was not seen for the use of 68Ga-PSMA PET/CT prior to sRT (p=0.789). Matched-pair analysis consisted of 95 pairs of PCa patients with or without PET/CT and no significant difference in BRFS based on the use of PET/CT was evident (p=0.884).ConclusionThis analysis did not show an improvement in BRFS using 68Ga-PSMA PET/CT prior to sRT neither for the entire cohort nor after matched-pair analysis after excluding patients with PET-positive lymph node or distant metastases a priori. As no improved BRFS resulted with implementation of 68Ga-PSMA PET in sRT planning, sRT should not be deferred until the best “diagnostic window” for 68Ga-PSMA PET/CT.
Highlights
68Ga-PSMA positron emission tomography (PET)/CT is associated with unprecedented sensitivity for localization of biochemically recurrent prostate cancer at low prostate-specific antigen (PSA) levels prior to radiotherapy
68Ga-PSMA PET/CT has a high impact on the management of biochemically recurrent prostate cancer as assessed by several retrospective and prospective analyses leading to changes in treatment in more than half of patients with biochemical recurrence [7, 8]
Patients with androgen deprivation therapy (ADT) were excluded resulting in a biochemical recurrence-free survival (BRFS) free of the influence of ADT. This multi-institutional analysis did neither confirm an improvement in BRFS for the entire cohort nor after matched-pair analysis nor for patients with PET-positive local recurrences using 68Ga-PSMA PET/ CT prior to salvage radiotherapy (sRT) compared to a pre-PSMA PET cohort after excluding patients with PET-positive lymph node or distant metastases a priori
Summary
Advances in novel positron emission tomography (PET) radiotracers for prostate cancer, above all 68Gallium-labeled ligands of the prostate-specific membrane antigen (68Ga-PSMA) are associated with unprecedented sensitivity for localization of biochemically recurrent prostate cancer at low PSA levels as shown by several meta-analyses of retrospective studies [5] and lately by a prospective multicentre trial including 635 patients [6]. This has been analysed so far by a few studies mostly without a comparator group of patients treated without prior 68Ga-PSMA PET/CT [9, 10]
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