Features of the physiological distribution of <sup>68</sup>Ga-PSMA and its importance in the differential diagnosis of metastatic lesions of lymph nodes in patients with prostate cancer

Introduction. The appearance of new radiopharmaceuticals based on prostate-specific membrane antigen has significantly increased the accuracy of prostate cancer diagnosis. The physiological accumulation of 68Ga-PSMA in the sympathetic ganglia is important in the diagnosis of metastatic lesions of the lymph nodes. Erroneous interpretation of images can lead to an incorrect choice of tactics for the treatment of prostate cancer.Purpose: improving the diagnosis of prostate cancer with the help of updated data on the physiological accumulation of 68GaPSMA. Identify the sources of potential errors in the interpretation of PET/CT with 68Ga-PSMA.Materials and methods. In order to stage the verified prostate cancer, PET was performed in our center/CT with 68Ga-PSMA in 109 men. All patients were divided into groups by the level of prostate-specific antigen, Gleason sum, and d’Amico.Results. In all patients, we observed the accumulation of RFP in the cervical, abdominal and presacral ganglia. The capture level of the radiotracer was in the range of SUV=1,6–2,3 (median SUV=1,9). In the control PET/CT study after treatment, the accumulation of RFP in the cervical, abdominal and presacral ganglia remained at the same values, which made it possible to identify the detected changes as a variant of the physiological norm.Conclusions. It is necessary to take into account the peculiarities of the physiological distribution and accumulation of radiotracer in organs and tissues, in particular, the capture of 68Ga-PSMA by sympathetic ganglia. This will avoid false-positive cases when describing PET-CT images and will make it possible to increase the informative value of the method.

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Prostate-specific membrane antigen (PSMA) PET-CT guided radiotherapy in oligometastatic prostate cancer.

Journal of Clinical Oncology ◽

10.1200/jco.2017.35.6_suppl.213 ◽

2017 ◽

Vol 35 (6_suppl) ◽

pp. 213-213

Author(s):

Benedikt Engels ◽

Ozan Cem Guler ◽

Cem Onal ◽

Mark De Ridder

Keyword(s):

Prostate Cancer ◽

Lymph Nodes ◽

Pelvic Bone ◽

Prostate Specific Membrane Antigen ◽

Ct Guided ◽

Castration Resistant ◽

Psma Pet ◽

Pet Ct ◽

Oligometastatic Prostate Cancer ◽

Specific Membrane

213 Background: Metastases-directed therapy by metastasectomy or radiotherapy (RT) might delay disease progression and postpone systemic treatment in patients with oligometastatic prostate cancer. Here, we evaluated retrospectively the efficacy and toxicity of 68Ga prostate-specific membrane antigen (PSMA) PET-CT guided radiotherapy (RT) in the treatment of oligometastatic prostate cancer. Methods: A total of 23 prostate cancer patients with biochemical relapse, of which 13 castration-sensitive and 10 castration-resistant, were treated with intensity-modulated and image-guided RT (IMRT-IGRT) on ≤ 3 metastases detected by 68Ga PSMA PET-CT. Androgen deprivation therapy was continued in castration-resistant patients. Local control (LC), progression-free survival (PFS) and overall survival (OS) were estimated with the Kaplan-Meier method. Results: A total of 38 metastases were treated. Involved sites were pelvic bone (n = 16), pelvic lymph nodes (n = 11), para-aortic lymph nodes (n = 6), ribs (n = 3) and vertebral body (n = 2). The median PSA prior to RT was 1.06 ng/ml (range 0.10 – 29.0 ng/ml). A median dose of 43.5 Gy (range, 30-64 Gy) was delivered by IMRT-IGRT in 12-27 fractions. At a median follow-up of 7 months (range, 2-17 months), 19 patients (83%) are in remission. Four patients (17%) developed distant recurrence. The actuarial 1-year LC, PFS and OS rates were 100%, 51% (95% CI 8-83%) and 100%. Castration-sensitive patients displayed a statistically significantly superior PFS on univariate analysis as compared to castration-resistant patients (1-year PFS 67% vs 0%, p < 0.01). One patient experienced grade 2 acute gastro-intestinal toxicity. No grade 3 or more toxic events were observed. Conclusions: By providing optimal LC, low toxicity and a promising PFS in castration-sensitive patients, the current retrospective study illustrated that 68Ga PSMA PET-CT guided RT may be an attractive treatment option in patients with oligometastatic prostate cancer. Validation by randomized trials is eagerly awaited.

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