Bladder cancer patients experience circulating tumor cell number surge during intramedullary nailing procedures intended for treating pathological fractures

Introduction and Objective: The goal of this study is to evaluate if intramedullary nailing procedure of completed or impending pathologic fractures in long bones secondary to metastatic bladder cancer affects the circulating tumor cell (CTC) number. Methods: Bladder cancer patients who presented with completed or impending pathologic fracture due to metastatic disease and underwent fracture fixation were recruited in this study. During nailing procedures performed by orthopedic oncologists, blood samples were collected from peripheral vein, peripheral artery and central vein at four time points (TP). TP1 was at the time of incision; TP2 was during the passage of the first reamer; TP3 was during wound closure; and TP4 was 24 hours post-operatively. Two CTC capture technologies were used: The FAST disk is a size-selective, clog-free rare cancer cell isolation platform (Clinomics, Ulsan, South Korea). CTCs were captured by a filter and stained with immunofluorescent antibodies. The filter was then scanned using the Metafer5 (MetaSystems, V3.11.8) automated scanning system to enumerate CTCs. The second platform was the AccuCyte-CyteFinder system (RareCyte, Inc., Seattle, WA), a selection-free method to enumerate and characterize CTCs from peripheral blood samples (PB) via immunofluorescent staining and scanning. The criteria for defining a CTC is DAPI positive, CK/EpCAM positive, and CD45 negative. Results: Three nailing cases from two patients were enrolled in this study (one patient had 2 affected limbs). The surgical sites were the right humerus (2 cases) and the right femur (3rd case). The AccuCyte-CyteFinder system was used for all three cases. FAST was used for the second and the third case. With the AccuCyte-CyteFinder system (TP1/TP2/TP3/TP4), the CTC counts were: 8/3314/7/2 for the first case; 259/3616/322/548 for the second case; 755/2507/917 CTCs for the third case (no TP4 sample). With FAST disk (TP1/TP2/TP3/TP4), the CTC counts were: 5/964/28/9 CTCs for the second case; 27/523/27/13 for the third case. Many CTC clusters were seen for TP2 venous samples, but rarely seen for the other samples. Conclusions: A surge in CTC number during the nailing procedure was observed in all cases by both methods. Our data suggest that the palliative nailing procedure may contribute to further CTC dissemination. Whether the surge of CTCs results in clinical relevant disease warrants further investigation. Citation Format: Zhongyuan Zhang, Liang Dong, Stephanie Glavaris, Emily Caruso, Kenneth Pienta, Carol Morris. Bladder cancer patients experience circulating tumor cell number surge during intramedullary nailing procedures intended for treating pathological fractures [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4597.