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Low risk and high risk recurrent prostate cancer in 3D Volumetric lymph node assessment based on CT and PSMA11-PET/CT

: Vinsensia, M.; Kratochwil, C.; Moltz, J.; Eiber, M.; Afshar-Oromieh, A.; Haberkorn, U.; Giesel, F.

European Journal of nuclear medicine 43 (2016), Supplement 1, S.S439-S440
ISSN: 0340-6997
ISSN: 1619-7070
ISSN: 1619-7089
European Association of Nuclear Medicine (EANM Annual Congress) <29, 2016, Barcelona>
Fraunhofer MEVIS ()

Introduction PSMA11-PET/CT is a powerful method of detecting early nodal metastases in patients with biochemical relapse. On this retrospective investigation the volume, dimensions and SUVmax of nodes identified by Glu-urea-Lys-(Ahx)-[68Ga(HBED-CC)] (68Ga-PSMA11) was evaluated and identified alongside their initial risk profile. Methods All PET/CT images were acquired 60±10 min after intravenous injection of 68Ga-PSMA-11 (mean dose 176 MBq). In 44 patients with recurrent prostate cancer and PSA relapse, 96 PSMA-positive lymph nodes were identified. These patients were classified based on their risk profile by the initial diagnosis in either low risk (Gleason Score≤6) or high risk group (Gleason Score>6). Fifty one PSMA-positive lymph nodes from 20 high risk patients and 45 PSMA-positive lymph nodes from 22 low risk prostate cancer patients were identified. Using semi-automated lymph node segmentation software (MeVis, Bremen, GER), the node volume, short and long axis dimensions were measured and compared to the maximum standardized uptake value (SUVmax). By morphologic criteria alone, round nodes greater than or equal to 10mmwould be considered positive, meanwhile lymph node with PSMA uptake (SUVmax) more than 2.0 would be considered PSMA-positive. Results The mean volume of 68Ga-PSMA-positive nodes in high risk group was 0.8 ml (range 0.3- 38.0 ml) and 0.6 ml (range 0.1-7.8 ml) in the low risk group. The mean short axis diameter in high risk group was 8.8 mm (range 4.1-36.0 ml) and 7.5 ml (range 2.1-22.0 ml) in the low risk group. High risk group presented mean SUVmax of 17.5 (range 3.1-102.4), meanwhile the low risk group′s mean SUVmax was 12.9 (range 2.7-74.3). From 51 PSMApositive lymph nodes from the high risk group, 21 lymph nodes (41%) were positive based on diameter >10mm on CT. Meanwhile on the low risk group, only 14 out of 45 PSMA-positive lymph nodes (31%) were positive based on the morphologic criteria. Based on PSMA11-PET/CT, 4 out of 20 patients (20%) from the high risk group and 10 out of 22 patients (45%) from the low risk group were upstaged from N0 to N1. These patients had PSMA-positive nodal metastases that are smaller than 10 mm and therefore missed by the conventional morphologic criteria. Conclusion 68Ga-PSMA-11 PET provides a better assessment of the nodal metastases status in patients with recurrent prostate cancer, especially in the low risk group. Morphological imaging strongly underestimates lymph-node involvement compared to PSMA-molecular staging in both, low- and high-risk group.