Abstract 693TiP
Background
Radical prostatectomy (RP) is as a standard-of-care treatment for localized and locally advanced prostate cancer. As advised by the guidelines of the European Association of Urology (EAU), RP is supplemented by an extended pelvic lymphadenectomy when a substantial risk for lymph node involvement exists. For pathological node-negative disease (pN0), the risk of biochemical recurrence (BCR) is defined by different features of the RP-specimen, such as the presence of extracapsular extension, seminal vesicle invasion (SVI) and/or positive surgical margins. For patients experiencing BCR, salvage radiation therapy (SRT) is considered to be the only curative treatment. Several factors predict for outcome after SRT: Gleason score (GS), pre-SRT PSA, pre-SRT doubling time, SVI, negative surgical margins, SRT dose and duration of adjuvant androgen deprivation therapy (ADT). The benefit in terms of BCR-free survival (FS) and metastasis-free survival (MFS) by adding 6 months of ADT to SRT has already been established. Retrospective evidence thereby suggests that a longer schedule of ADT may be more beneficial compared to 6 months.
Trial design
LOBSTER (LOng term Better than Short-TErm ADT with salvage Radiotherapy) is a phase 2b trial, investigating the question whether prolonging the duration of ADT (triptorelin) from 6 to 24 months, when added to SRT significantly improves MFS (primary endpoint). Patients who are experiencing BCR after RP with pN0-status at the original RP-specimen will be randomized with a 1:1 allocation ratio and stratified by SVI (present/absent), PSA doubling time (≤1 year/>1year), GS (<8 or ≥8) and section margin positivity (present/absent). A total of 394 patients will included. This number of patients is needed to detect a significant difference of 10 % at 5 years (p<0.05) with a power of 80%. BCR is defined as a PSA-rise post-RP to ≥ 0.2 ng/ml. However, in case of Gleason 8-10, pT3b or R1 resection, a PSA ≥ 0.15 ng/ml is allowed for inclusion. Testosterone level should be above 150 ng/dl. Patients must have a good performance status (ECOG 0-1) and life expectancy of >5 years. The first patient is expected to be randomized in June 2020.
Clinical trial identification
NCT04242017.
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.