Abstract
PurposeTo assess the outcome of radiotherapy (RT) to all PSMA ligand positive metastases for patients with castrate-resistant prostate cancer (mCRPC).Patients and methodsA total of 42 patients developed oligometastatic mCRPC and received PSMA PET-guided RT of all metastases. The main outcome parameters were biochemical progression-free survival (bPFS), and second-line systemic treatment free survival (SST-FS).ResultsA total of 141 PSMA ligand-positive metastases were irradiated. The median follow-up time was 39.0 months (12-58 months). During the follow-up five out of 42 (11.9%) patients died of progressive mPCa. Five out of 42 (11.9%) patients showed no biochemical responses and presented with a PSA level ≥10% of the baseline PSA at first PSA level measurement after RT and were classified as non-responders. The median PSA level before RT was 4.79 ng/mL (range, 0.4-46.1), which decreased significantly to a median PSA nadir level of 0.39 ng/mL (range, <0.07-32.8; p=0.002). The median PSA level at biochemical progression after PSMA ligand-based RT was 2.75 ng/mL (range, 0.27-53.0; p=0.24) and was not significantly different (p=0.29) from the median PSA level (4.79 ng/mL, range, 0.4-46.1) before the PSMA ligand-based RT. The median bPFS was 12.0 months after PSMA ligand PET-based RT (95% CI, 11.2-15.8) and the median SST-FS was 15.0 months (95% CI, 14.0-21.5).ConclusionIn well-informed and closely followed-up patients, PSMA PET-guided RT represents a viable treatment option for patients with oligometastatic mCRPC to delay further systemic therapies.
Highlights
The cornerstone of treatment for metastatic castrate-resistant prostate cancer is either cytotoxic chemotherapy, androgen biosynthesis inhibition, androgen receptor inhibition, or radium-223
The median biochemical progression-free survival (bPFS) was 12.0 months after prostate-specific membrane antigen (PSMA) ligand positron emission tomography (PET)-based RT and the median SSTFS was 15.0 months
One hundred and forty-one PSMA ligand-positive metastases were detected and treated with RT: Pelvic nodal metastases accounted for 37.6% (53/141), while 18.4% (26/141) allocated in paraaortic node metastases, 7.8% (11/141) in distant lymph node metastases, 28.4% (40/141) in bone metastases, 1.4% (2/141) in visceral metastases, and 6.4% (9/141) in local prostatic fossa relapses
Summary
The cornerstone of treatment for metastatic castrate-resistant prostate cancer (mCRPC) is either cytotoxic chemotherapy, androgen biosynthesis inhibition (e.g. abiraterone), androgen receptor inhibition (enzalutamide), or radium-223. A small subgroup of patients with oligoprogression, defined as the development or progression of a limited number of lesions, might be controlled by radiotherapy as a metastasis-directed therapy (MDT) when targeting all lesions [2] These patients may continue on ADT for a defined period until further disease progression requires second-line systemic treatment (SST) [3]. The recent introduction of prostate-specific membrane antigen (PSMA)-ligand positron emission tomography (PET) has substantially improved the diagnostic accuracy of staging at low prostate-specific antigen (PSA) levels [4,5,6,7,8] This technique yields further refined and well-monitored individualized radio-oncological treatment schemes which aim to improve PSA kinetics, prolong the progression-free survival and potentially defer the initiation of systemic therapies for patients with hormone-sensitive metastatic prostate cancer (mPCA) [9,10,11,12,13,14]. Data on the feasibility and clinical outcome of MDT guided by PSMA-targeted imaging in mCRPC are limited
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