In-vivo imaging of cellular proliferation in renal cell carcinoma using 18F-Fluorothymidine (FLT) PET

  • Dr Peter Wong, Department of Surgery and Urology, University of Melbourne; Ludwig Institute for Cancer Research, Austin Hospital, Victoria, Australia
  • Dr Sze Ting Lee, Centre for PET; Ludwig Institute for Cancer Research; Department of Medicine, University of Melbourne, Austin Hospital, Vic, Australia
  • Dr Carmel Murone, Ludwig Institute for Cancer Research, Austin Hospital, Victoria, Australia
  • Dr John Eng, Centre for PET, Austin Hospital, Victoria, Australia
  • Dr Nathan Lawrentschuk, Department of Surgery and Urology, University of Melbourne, Austin Hospital, Victoria, Australia
  • Dr Salvatore Berlangieri, Centre for PET, Austin Hospital, Victoria, Australia
  • Ms Kunthi Pathmaraj, Centre for PET, Austin Hospital, Victoria, Australia
  • Dr Graeme O'Keefe, Centre for PET, Austin Hospital, Victoria, Australia

    • Background: The ability to measure cellular proliferation non-invasively in renal cell carcinoma may allow prediction of tumour aggressiveness and response to therapy. The aim of this study was to evaluate the uptake of 18F-fluorothymidine (FLT) in renal cell carcinoma, and to compare this to 18F-fluorodeoxyglucose (FDG), and to an immunohistochemical measure of cellular proliferation (Ki-67).

    Methods: Twenty seven patients (16 men, 11 women; age 42-77) with newly diagnosed renal cell carcinoma suitable for resection were prospectively enrolled. All patients had preoperative FLT and FDG PET scans. After surgery tumour was taken for histologic analysis and immunohistochemical staining by Ki-67.

    Results: The mean SUVmax (maximum standardized uptake value) ± SD for FLT in tumour was 2.53 ± 1.26, compared to normal kidney (2.47 ± 0.34). The mean SUVmax for FDG in tumour was similar to FLT (2.60 ± 1.08). Visual identification of tumour using FLT PET compared to normal kidney was facilitated by the use of a pre-operative contrast enhanced CT scan. There was a significant correlation between FLT uptake and the immunohistochemical marker Ki-67 (r=0.624, p=0.0008) in RCC. Ki-67 labelling index was mean ± SD of 13.3% ± 9.2 (range 2.2% to 36.3%).

    Conclusion: There is detectable uptake of FLT in primary renal cell carcinoma, which correlates with cellular proliferation as assessed by Ki-67 labelling index. This finding has relevance to the use of FLT PET in molecular imaging studies of renal cell carcinoma biology.