[68Ga]PSMA-HBED PET for differential diagnosis of suspicious lung lesions in patients with prostate cancer

RATIONALE - In prostate cancer (PC) patients, differentiation between lung metastases and lesions of different origin, e.g. primary lung cancer, is a common clinical question. Herein we investigate the use of (68)Ga-PSMA-HBED-CC for this purpose.

METHODS - 1889 PC patients receiving (68)Ga-PSMA PET/CT or PET/MR scans were evaluated retrospectively for suspicious lung lesions. For up to 5 lesions per patient, location, CT diameter, CT morphology and SUVmax values were determined. Standard for classification was either histopathologic evaluation or, in case of PC metastases, responsivity to anti-hormone therapy. Comparison of the different classes was executed by Student's t test. PSA and PSMA immunohistochemistry were performed if histologic samples were available; (68)Ga-PSMA autoradiography was performed on an exemplary case of PET positive lung cancer.

RESULTS - 89 lesions in 45 patients were identified, of which 76 were classified as PC (39 proven, 37 highly probable), 7 as primary lung cancer and 2 as activated tuberculosis; 4 lesions remained unclear. The mean SUVmax was 4. 4±3. 9 for PC metastases and 5. 6±1. 6 for primary lung cancer (P = 0. 408). Additionally, substantial differences in SUVmax values intra-individually were detected. The two tuberculous lesions showed an SUVmax of 7. 8 and 2. 5, respectively. Using immunohistochemistry, we could demonstrate PSMA expression in the neo-vasculature of several PSMA PET positive lung cancers, as well as in tuberculous lesions from our histologic database.

CONCLUSION - Quantitative (SUV) analysis of (68)Ga-PSMA PET was not able to discriminate reliably between pulmonary metastases and primary lung cancer in PC patients. The reason for the unexpectedly high tracer uptake in non-PC lesions is not completely clear. PSMA expression in neo-vasculature provides a possible explanation for this finding; however, other contributing factors, such as tracer binding to proteins other than PSMA, cannot be excluded at present.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2015 Nov 19 [Epub ahead of print]

Thomas Pyka, Gregor Weirich, Ingo Einspieler, Tobias Maurer, Joerg Theisen, Georgios Hatzichristodoulou, Kristina Schwamborn, Markus Schwaiger, Matthias Eiber

Technische Universität München, Germany. , Technische Universität München, Germany. , Technische Universität München, Germany. , Technische Universität München, Germany. , Technische Universität München, Germany. , Technische Universität München, Germany. , Technische Universität München, Germany. , Technische Universität München, Germany. , Technische Universität München, Germany.

PubMed