Among patients with prostate cancer, tumor relapse after primary therapy particularly occurs in high-risk groups. The standard of care for distant relapse of prostate cancer is androgen-deprivation therapy (ADT), which has a negative impact on the patient's quality of life (1). Recently alternative local treatment strategies have been proposed for patients with oligometastatic disease, who have a better prognosis than patients with extensive disease (2). Local therapies such as radiotherapy could provide effective local control, delay disease progression and therefor reduce the need to initiate systemic therapies (3). The identification of patients with oligometastatic prostate cancer is challenging due to the lack of sufficiently sensitive imaging for detection of low-volume recurrent and metastatic disease in patients with low prostatespecific antigen (PSA) levels (2). In general, positronemission tomography-computed tomography (PET/CT) for radiotherapy has proven helpful in patient selection and target volume delineation, with promising results regarding clinical outcome and toxicity (4, 5). A new diagnostic option in this context is the use of prostate-specific membrane antigen (PSMA) ligands for PET/CT. 68 Ga-PSMA ligand PET/CT has been reported to have a substantially higher diagnostic accuracy for the detection of prostate cancer metastases than choline-based PET/CT, particularly in the case of lymph node metastases (6-10). Data on the effectiveness of 68 Ga-PSMA ligand PET/CT-based radiotherapy for prostate cancer lymph node metastases after primary therapy are limited.The aim of the present study was to assess the clinical outcome and time of initiation of systemic therapies (ADT or chemotherapy) of patients with isolated prostate cancer lymph node metastases after primary therapy treated with 68 Ga-labelled PSMA ligand PET/CT-guided 3D conformal radiotherapy.
Patients and MethodsStudy population. Between June 2014 and March 2016, 23 patients with biochemical failure and a PSA above 0.5 ng/ml after primary therapy of prostate cancer underwent 68 Ga-PSMA ligand PET/CT for restaging purposes and were treated with radiotherapy of the 68 Ga-PSMA ligand PET/CT-positive lymph nodes. All cases were discussed 1273