DETERMINATION OF SKELETAL TUMOR BURDEN ON 18F-FLUORIDE PET/CT

The purpose of this study was to define a method for assessing skeletal tumor burden with (18)F-sodium fluoride PET/CT (fluoride-PET/CT) and evaluate the reproducibility of these measurements.

METHODS: Ninety-eight consecutive patients (90 males; 65.7 ± 14.2yrs.) underwent 158 fluoride-PET/CT scans for evaluation of skeletal metastatic disease. Normal bone mean SUVs were measured over a 1 cm spherical volume of interest (VOI) placed over 5 bone sites: T12, L5, sacrum, right iliac and right femur. For each patient, average SUVs for all sites was generated. Afterwards, a threshold value of normal bone uptake was established. Subsequently, skeletal tumor burden was determined by generating volumetric data using a whole-body segmentation method. All SUVs below the established normal threshold value were excluded from analysis as were VOIs not related to metastatic disease. Statistics for the remaining VOIs were then generated and defined as the skeletal tumor burden by two parameters: total fluoride skeletal metastatic lesion uptake (TLF10) and the total volume of fluoride avid bone metastases (FTV10). TLF10 and FTV10 reproducibility was determined using two independent and experienced PET/CT readers performing analysis on a subset of 13 fluoride-PET/CTs.

RESULTS: Average ± SD of normal bone SUV values were: T12 = 6.62 ± 1.55, L5 = 6.11 ± 1.73, sacrum = 4.59 ± 1.74, right iliac = 5.39 ± 1.72 and right femur = 3.90 ± 1.57. The average normal SUV for all 543 sites was 5.32 ± 0.99. Based on these values, a threshold of SUVmax=10 was chosen to exclude normal bone from the volumetric calculations. Semi-automated measurements of total fluoride activity above an SUV of 10 (TLF10 and FTV10) exhibited high inter-observer reproducibility, within ±0.77% and ±3.62% of the inter-reader average for TLF10 and FTV10, respectively.

CONCLUSION: Determination of skeletal tumor burden with fluoride-PET/CT is feasible and highly reproducible. Using an SUV threshold of 10 excludes nearly all normal bone activity from volumetric calculations.
Copyright © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2015 Jul 01 [Epub ahead of print]

Eric M Rohren, Elba Etchebehere, John Araujo, Brian Paul Hobbs, Nancy Swanston, Michael Everding, Tracy Moody, Homer A Macapinlac

The University of Texas MD Anderson Cancer Center, United States;, The University of Texas MD Anderson Cancer Center, United States;, The University of Texas MD Anderson Cancer Center, United States;, The University of Texas MD Anderson Cancer Center, United States;, The University of Texas MD Anderson Cancer Center, United States;, The University of Texas MD Anderson Cancer Center, United States;, The University of Texas MD Anderson Cancer Center, United States;, University of Texas M. D. Anderson Cancer Center, United States.

PubMed

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