Risk Factors for Biochemical Recurrence After PSMA-PET-Guided Definitive Radiotherapy in Patients With De Novo Lymph Node-Positive Prostate Cancer
Simon K. B. Spohn, Viktoria Birkenmaier, Juri Ruf, Michael Mix, August Sigle, Erik Haehl, Sonja Adebahr, Tanja Sprave, Eleni Gkika, Alexander Rühle, Nils H. Nicolay, Simon Kirste, Anca‐Ligia Grosu, Constantinos Zamboglou
Abstract
Introduction The National Comprehensive Cancer Network recommends external beam radiotherapy (EBRT) combined with androgen deprivation therapy (ADT) as the preferred treatment option for newly diagnosed node-positive (cN1) prostate cancer (PCa) patients. However, implementation of positron emission tomography targeting prostate-specific membrane antigen (PSMA-PET) in the staging of primary PCa patients has a significant impact on RT treatment concepts. This study aims to evaluate outcomes and their respective risk factors on patients with PSMA-PET-based cN1 and/or cM1a PCa receiving primary RT and ADT. Methods Forty-eight patients with cN0 and/or cM1a PCa staged by [ 18 F]PSMA-1007-PET ( n = 19) or [ 68 Ga]PSMA-11-PET ( n = 29) were retrospectively included. All patients received EBRT to the pelvis ± boost to positive nodes, followed by boost to the prostate. The impact of different PET-derived characteristics such as maximum standard uptake value (SUVmax) and number of PET-positive lymph nodes on biochemical recurrence-free survival (BRFS) (Phoenix criteria) and metastasis-free survival (MFS) was determined using Kaplan–Meier and Cox proportional hazard regression analyses. Results Median follow-up was 24 months. Median initial serum prostate-specific antigen was 20.2 ng/ml (IQR 10.2–54.2). Most patients had cT stage ≥ 3 (63%) and ISUP grade ≥ 3 (85%). Median dose to the prostate, elective nodes, and PET-positive nodes was 75 Gy, 45 Gy, and 55 Gy, respectively. Ninety percent of patients received ADT with a median duration of 9 months (IQR 6–18). In univariate analysis, cM1a stage ( p = 0.03), number of >2 pelvic nodes ( p = 0.01), number of >1 abdominal node ( p = 0.02), and SUVmax values ≥ median (8.1 g/ml for 68 Ga-PSMA-11 and 7.9 g/ml for 18 F-PSMA-1007) extracted from lymph nodes were significantly associated with unfavorable BRFS, but classical clinicopathological features were not. Number of >2 pelvic nodes ( n = 0.03), number of >1 abdominal node ( p = 0.03), and SUVmax values ≥ median extracted from lymph nodes were associated with unfavorable MFS. In multivariate analysis, number of >2 pelvic lymph nodes was significantly associated with unfavorable BRFS (HR 5.2, p = 0.01) and SUVmax values ≥ median extracted from lymph nodes had unfavorable MFS (HR 6.3, p = 0.02). Conclusion More than 2 PET-positive pelvic lymph nodes are associated with unfavorable BRFS, and high SUVmax values are associated with unfavorable MFS. Thus, the number of PET-positive lymph nodes and the SUVmax value might be relevant prognosticators to identify patients with favorable outcomes.