PD51-02 PLANNED SECONDARY ANALYSIS OF PURE-01

Abstract

INTRODUCTION AND OBJECTIVE: FDG-PET/CT has limited utility in clinical N0 (cN0) patients (pts) with MIBC who receive neoadjuvant chemotherapy and RC or RC alone (Dason, AUA19). We present a secondary analysis aimed at evaluating the role of PET/CT in lymph node (LN) involvement assessment. METHODS: In PURE-01 (NCT02736266), 3 courses of 200 mg pembrolizumab, every 3 weeks, were administered prior to RC. Pts were assessed with thorax-abdomen CT scan and with PET/CT scan during screening and after treatment, before RC. Imaging review and analysis was performed by two experienced nuclear medicine physicians blinded to clinical information. Semiquantitative and volumetric analysis was performed. For each patient with LN increased uptake in abdomino-pelvic area, the SUVmax and the short-axis size of the most intense LN were recorded. All pts underwent templated pelvic LN dissection (LND) with packeted node submission. PET/TC diagnostic ability was assessed using sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy. RESULTS: From 02/17 to 06/2019, 114 pts were enrolled ad treated. 11 pts received additional chemotherapy post-pembrolizumab and were excluded from the analyses, resulting in 103 total evaluable pts (and 206 PET/TC scans). Six pts (5.8%) had positive nodes at baseline PET/CT: mean SUVmax=2.75; mean short axis: 6.2 mm. Eight pts (7.8%) had positive LN at PET/CT post-pembrolizumab: mean SUVmax=4.21; mean short axis: 7.2mm. The rate of pathologic LN positive (pN+) disease was 15.5% (16 pts). The performance of post-pembrolizumab PET/CT in predicting pN+ disease is indicated in the Table. 4/6 pts (66.7%) with baseline FDG uptake revealed as pN+ vs 12/97 (12.4%) with no baseline FDG uptakes (p=0.005). A total of 39 pts (37.9%) developed inflammatory FDG-uptakes post-pembrolizumab in several target organs/regions: top 5 sites were thyroid (N=21, 61.8%), stomach and mediastinum (13 pts each, 12.6%), lung (N=10, 9.7%), other lymph nodes (N=4, 3.9%). These changes were clinically evident (signs/symptoms or laboratory changes) in 15 pts (38.5%). CONCLUSIONS: Criteria for eligibility of cN0 pts to single-agent neoadjuvant pembrolizumab trials may be enhanced with PET/CT use. Three cycles of pembrolizumab determined profound inflammatory changes, whose long-term impact on safety is still to be determined.Source of Funding: None