Repeatability of tumour perfusion measurement with [15O]H2O PET in prostate cancer.

BACKGROUND: Tumour perfusion is a universal cancer biomarker with potential value in characterising primary prostate tumours and longitudinal measurements for evaluation of treatment response. To evaluate whether a change in perfusion is significant, the reproducibility of the measurement must be known. [15O]H2O positron emission tomography (PET) is the gold standard for non-invasive quantitative perfusion imaging, however repeatability data on prostate cancer are currently unavailable. Hence, the aim of the present study is to determine the repeatability of [15O]H2O tumour perfusion in prostate cancer. RESULTS: Thirteen well-defined MRI PI-RADS lesions from ten patients were studied. The repeatability of [15O]H2O K1 was 30% using both parametric image calculation and volume of interest (VOI)-based analysis. Intraclass correlation coefficient (ICC) was 0.89 and 0.91 for parametric image calculation and VOI-based analysis, respectively. A study sample size of 10 patients should be sufficient for detecting a relative change of 20% over time. CONCLUSIONS: [15O]H2O tumour perfusion in localised prostate cancer can be measured with a high repeatability, showing comparable performance when using parametric K1 perfusion maps and VOI-based analysis. For longitudinal evaluation, changes above 30% are likely to represent actual changes in tumour perfusion, for example as response to a specific treatment.