Abstract
BackgroundIn case of oligo-recurrent prostate cancer (PC) following prostatectomy, 68Ga-PSMA-PET/CT can be used to detect a specific site of recurrence and to initiate metastasis-directed radiation therapy (MDT). However, large heterogeneities exist concerning doses, treatment fields and radiation techniques, with some studies reporting focal radiotherapy (RT) to PSMA-PET/CT positive lesions only and other studies using elective RT strategies. We aimed to compare oncological outcomes and toxicity between PET/CT-directed RT (PDRT) and PDRT plus elective RT (eRT; i.e. prostate bed, pelvic or paraaortal nodes) in a large retrospective multicenter study.MethodsData of 394 patients with oligo-recurrent 68Ga-PSMA-PET/CT-positive PC treated between 04/2013 and 01/2018 in six different academic institutions were evaluated. Primary endpoint was biochemical-recurrence-free survival (bRFS). bRFS was analyzed using Kaplan–Meier survival curves and log rank testing. Uni- and multivariate analyses were performed to determine influence of treatment parameters.ResultsIn 204 patients (51.8%) RT was directed only to lesions seen on 68Ga-PSMA-PET/CT (PDRT), 190 patients (48.2%) received PDRT plus eRT. PDRT plus eRT was associated with a significantly improved 3-year bRFS compared to PDRT alone (53 vs. 37%; p = 0.001) and remained an independent factor in multivariate analysis (p = 0.006, HR 0.29, 95% CI 0.12–0.68). This effect was more pronounced in the subgroup of patients who were treated with PDRT and elective prostate bed radiotherapy (ePBRT) with a 3-year bRFS of 61% versus 22% (p <0.001). Acute and late toxicity grade ≥3 was 0.8% and 3% after PDRT plus eRT versus no toxicity grade ≥3 after PDRT alone.ConclusionsIn this large cohort of patients with oligo-recurrent prostate cancer, elective irradiation of the pelvic lymphatics and the prostatic bed significantly improved bRFS when added to 68Ga-PSMA-PET/CT-guided focal radiotherapy. These findings need to be evaluated in a randomized controlled trial.
Highlights
Primary, curative treatment of localized prostate cancer (PC) can be performed with either radical prostatectomy (RP) or radiation therapy (RT)
In the STOMP trial the primary endpoint, median ADT-free survival, was improved from 13 to 21 months with metastases-directed therapy (MDT) and in the ORIOLE trial MDT was associated with an improved progression-free survival (HR 0.3, 95% CI 0.11–0.81)
In patients without macroscopically local recurrence after RP, we evaluated the impact of PET/CT-directed RT (PDRT) alone versus elective prostate bed Radiation Therapy (RT) plus PDRT
Summary
Curative treatment of localized prostate cancer (PC) can be performed with either radical prostatectomy (RP) or radiation therapy (RT). In the case of a biochemical relapse after RP, which occurs in up to 50% depending on stage and adverse factors [1, 2], salvage RT of the prostatic bed is performed to achieve longterm disease control in terms of biochemical relapse-free survival (bRFS) as well as cancer specific survival [3]. The rationale for metastases-directed therapy (MDT) is to eradicate all visible disease locations with high doses to delay the use of androgendeprivation-therapy (ADT) or even prolong progression-free survival while limiting side effects that could potentially occur by the use of larger radiation treatment fields [5]. In case of oligo-recurrent prostate cancer (PC) following prostatectomy, 68Ga-PSMA-PET/CT can be used to detect a specific site of recurrence and to initiate metastasis-directed radiation therapy (MDT). We aimed to compare oncological outcomes and toxicity between PET/CT-directed RT (PDRT) and PDRT plus elective RT (eRT; i.e. prostate bed, pelvic or paraaortal nodes) in a large retrospective multicenter study
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