@article {Rahbar469, author = {Kambiz Rahbar and Katharina Kessel and Matthias Weckesser and Michael Schaefers and Wolfgang Roll and Robert Seifert and Verena Humberg and Martin Boegemann and Christoph Bernemann}, title = {Prospective analysis of circulating tumor cell mRNA in patients with mCRPC and correlation with PSMA targeted imaging and therapy: Preliminary results}, volume = {60}, number = {supplement 1}, pages = {469--469}, year = {2019}, publisher = {Society of Nuclear Medicine}, abstract = {469Background: PSMA targeted imaging and therapy of prostate cancer has changed the management of prostate cancer patients. The aim of the present study was to evaluate circulating tumor cells (CTC) for expression of PSMA. This and other available biomarkers were analyzed as predictors of response to Lu-177-PSMA-617 radioligand therapy (RLT). Methods: Nineteen consecutive patients, median age 68.8 years (range: 56.9 - 83.3) with metastatic castration-resistant prostate cancer (mCRPC) were prospectively included in this study. Median Gleason Score was 9 (Range: 7-9). Total tumor volume in PSMA targeted PET/CT, initial PSA, ALP, LDH, PSMA mRNA and androgen receptor splice variant AR-V7 were evaluated at baseline, compared with each other, and correlated with response to PSMA RLT. Results: A total of 57 cycles of Lu-177-PSMA-617 (median 7.4 GBq, range 5.8-8.2) and median of 3 cycles per patient were performed. Follow-up data were available for 18 patients. The majority of patients (89\%) presented with bone metastases, 68\% with lymph node metastases, and 21\% with visceral metastases. Patients had received docetaxel, either abiraterone or enzalutamide or both in 78\%, 100\% and 63\%. Any PSA decline was seen in 15 (79\%) and a decline >=50\% and >=30\% in 8 (42\%) and 12 (63\%) of the patients, respectively. There was a significant correlation between initial PSA, PSMA mRNA expression, total tumor volume and AR-V7 at baseline, but none of these parameters predicted response to PSMA RLT. Conclusions: PSMA mRNA expression might predict total tumor volume and correlates with initial PSA and androgen receptor splice variant expression. However, none of these parameters was predictive for response. Further studies to evaluate the potential of PSMA protein on the CTC surface in combination to next generation sequencing approaches (both RNA and DNA) are warranted.}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/60/supplement_1/469}, eprint = {https://jnm.snmjournals.org/content}, journal = {Journal of Nuclear Medicine} }