Clinical value of negative 68Ga-PSMA PET/CT in the management of biochemical recurrent prostate cancer patients.

To evaluate the clinical value of 68Ga-PSMA PET/CT negativity in patients with biochemical recurrent prostate cancer (BCR).

One hundred three BCR patients (median age, 70 years; median PSA, 0. 47 ng/mL) with negative 68Ga-PSMA PET/CT, followed up for at least 1 year, were retrospectively identified in a database of 1003 consecutive patients undergoing 68Ga-PSMA PET/CT for BCR. Clinical recurrence (CR) was determined or excluded on follow-up imaging selected as per clinical practice. Clinical recurrence-free survival (CRFS) was computed from the date of negative 68Ga-PSMA PET/CT to the date of evident disease; frequencies of CRFS were described as per ISUP patient subset (subset 1: ISUP grades 1 and 2; subset 2: ISUP grade 3; subset 3: ISUP grades 4 and 5) and other conventional variables.

In 57 patients out of 103 (55.3%), CR was detected in the prostatic fossa (45.6%), nodes (38.6%), and bone (15.8%). The median CRFS was 15.4 months (range, 12.1-20.5), with a CRFS at 12 months in 61.4% of cases (range, 50.9-70.4) whereas the 24-month CRFS was 34.8% (range, 24-45.8). ISUP subset 1 benefited from significantly longer CRFS compared to subset 2 and subset 3 (median CRFS, 20.5 months, 12.6 months, and 12.1 months, respectively). ISUP subset 3 had significantly poorer 24-month CRFS (9.3%) compared to subset 1 (47.8%) and subset 2 (33.5%). At the univariate and multivariate analyses, the ISUP subset was the only significant risk factor for clinical relapse; ISUP subset 3 and subset 2 patients held a higher risk of CR compared to subset 1 patients (HR of 2.75 [1.35-5.57] for subset 3 versus subset 1; HR of 2.08 [1.11-3.88] for subset 2 versus subset 1).

68Ga-PSMA PET/CT negativity in early BCR patients (PSA < 0.5 ng/mL) with low-grade primary prostate cancer (ISUP1 and 2) may support the exploration of a clinical surveillance approach in future prospective studies.

European journal of nuclear medicine and molecular imaging. 2020 Jun 26 [Epub ahead of print]

M Celli, U De Giorgi, P Caroli, V Di Iorio, L Fantini, V Rossetti, F Foca, S Nicolini, M Giganti, G Paganelli, F Matteucci

Nuclear Medicine Unit, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy., Department of Medical Oncology, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy., Oncology Pharmacy, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy., Unit of Biostatistics and Clinical Trials, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy., Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy., Nuclear Medicine Unit, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy. .