TY - JOUR T1 - <strong><sup>18</sup></strong><strong>F-PSMA-1007 PET/CT for response assessment in patients with metastatic renal cell carcinoma undergoing tyrosine-kinase and check-point inhibitor therapy - preliminary results</strong> JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1269 LP - 1269 VL - 61 IS - supplement 1 AU - Lena Mittlmeier AU - Marcus Unterrainer AU - Andrei Todica AU - Clemens Cyran AU - Severin Rodler AU - Peter Bartenstein AU - Christian Stief AU - Michael Staehler AU - Harun Ilhan Y1 - 2020/05/01 UR - http://jnm.snmjournals.org/content/61/supplement_1/1269.abstract N2 - 1269Introduction: The introduction of tyrosine-kinase and check-point inhibitors prolonged overall survival for metastatic renal-cell carcinoma (mRCC). However, serum biochemistry is unable to predict their therapeutic efficacy. Early prediction of treatment response is highly desirable for the individualization of patient management and improvement of therapeutic outcome. Initial data showed promising results for the value of PSMA-targeted PET imaging in mRCC. We evaluated the value of 18F-PSMA-1007 PET imaging for response assessment in patients undergoing tyrosine-kinase and check-point inhibitor therapy for mRCC in comparison to CT as the current imaging reference standard. Methods: Contrast-enhanced 18F-PSMA-1007 PET/CT was performed in mRCC patients prior to initiation of systemic treatment and 8 weeks after therapy initiation. Radiographic treatment response was evaluated separately on 18F-PSMA PET and high-dose CT. Changes in uptake on PSMA-PET (SUVmean) were assessed on a per-patient basis using a modified PERCIST scoring system. Complete response (CRPET) was defined as absence of any uptake in all target lesions on posttreatment PSMA-PET. Partial response (PRPET) was defined as decrease in summed SUVmean of &gt;30%. The appearance of a new PET-positive lesion or an increase in summed SUVmean of &gt;30% was defined as progressive disease (PDPET). A change in summed SUVmean of ±30% was classified as stable disease (SDPET). RECIST 1.1 criteria were used for treatment response assessment on CT. Subsequently, the results of radiographic response assessment on PSMA-PET and CT were compared. Results: Overall, 10 mRCC patients prior to and during systemic treatment were included. At initial PSMA-PET, all mRCC patients showed at least one PSMA-avid lesion. On follow-up PET, 3 patients showed CRPET, 3 PRPET, 3 SDPET and 1 PDPET. According to RECIST 1.1, only 3 patients showed PRCT, 6 SDCT and 1 PDCT. Overall, concordant classifications were found in only 2 cases (SD and PD). Patients with CRPET on PET were classified as 1 PRCT and 2 SDCT on CT using RECIST 1.1. By contrast, 2 patients classified as PRCT on CT showed PSMA-uptake without major changes during therapy (SDPET). However, among 6 patients with SDCT on CT, 2 were classified as CRPET, 3 as PRPET and only 1 as SDPET on PSMA-PET. Clinical data in terms of overall-survival will be evaluated within the further disease course. Conclusion: On PSMA-PET heterogenous courses could be observed during systemic treatment in mRCC patients with highly diverging results compared to RECIST 1.1. Changes in PSMA-avidity during treatment have to be correlated with the further disease course. PSMA-PET for response assessment in mRCC patients might provide information during therapy beyond the morphologic information on CT that might highly influence patient management. ER -