PD54-09 BIOCHEMICAL RECURRENCE OF PROSTATE CANCER

Abstract

INTRODUCTION AND OBJECTIVE: Clinical approach of prostate cancer (PCa) biochemical recurrence (BCR) is nowadays being questioned. Prostate-specific membrane antigen positron scan (PSMA PET) has shown good potential in this field. The aim is to evaluate PSMA PET accuracy in BCR and its utility on clinical outcome. METHODS: Of 319 patients with PCa who underwent 68-Ga PSMA PET between October 2015 and June 2019, 70 had BCR after treatment with curative intent. Two groups were created: Group submitted to surgery (GS) (N:48; 68.6%) and Group submitted to radiotherapy (GR) (N:22; 31.4%). Clinical, analytical, pathological and PSMA PET results were evaluated. RESULTS: Initial age was different (GS – 66±6.5 vs GR – 69±6.2 years, p=0.008). Initial PSA was similar (8.7±5.7 vs 7.5±5.8 ng/mL, p=0.4). GS patients were mainly at intermediate risk (85.1% vs 42.9%, p=0.001) while GR patients were at low risk of recurrence (8.5% vs 47.6%, p=0.001). In GS and GR, PSMA PET detected, respectively, pelvic relapse in 31.3% and 63.6%, and extrapelvic relapse in 18.8% and 31.8%. PSMA PET was negative in 50% (n=24) of GS and 4.5% (n=1) of GR. In positive PSMA PET, PSA was similar in pelvic and extrapelvic disease in both groups (p=0.6; p=0.2). Salvage treatment was performed in 61.9% (n=26) of GS (local radiotherapy in 54.7%, radiotherapy to a single bone metastasis in 2.4% and lymphadenectomy in 4.8%) and in 15% (n=3) of GR (radical prostatectomy with bilateral pelvic lymphadenectomy in 10% and high-dose brachytherapy in 5%), p<0.001. From GS patients submitted to salvage treatment, 59.1% returned to complete remission. Concerning these patients, local radiotherapy led to complete remission in 68.4% (N=13). Neither extended lymphadenectomy nor radiotherapy to the single bone metastasis led to complete remission. The removed ganglia did not harbour tumour. From GR patients submitted to salvage treatment, two had complete remission and one had partial remission (case of high-dose brachytherapy). Concerning diagnostic accuracy, PSMA PET was positive for pelvic relapse when pre-PET PSA≥0.8ng/mL (GS) or ≥2.3ng/mL (GR) and for extrapelvic relapse when PSA≥ 0.4ng/mL (GS) or ≥3.5ng/mL (GR), p> 0.05. CONCLUSIONS: When PSMA PET was positive, PSA was similar between patients with pelvic and extrapelvic relapse. Biochemical persistence rate after salvage therapy was similar (30-40%). The cut-off PSA values for pelvic relapse detected on PSMA PET were ≥0.8 ng/mL (GS) and ≥2.3ng/mL (GR). Source of Funding: None