C. SAMBAZIOTIS ET AL.19
0.24). Furthermore, our study demonstrates that benign
lesions do not have progressively increasing uptake on
multiple time point FDG PET unlike metabolically active
malignant lesions as shown in the prior studies. Thus, for
benign osteochondromas, the addition of a triple time
point did not provide additional clinical utility.
The use of imaging modalities such as ultrasound, CT
or MRI to differentiate benign osteochondromas from
secondary chondrosarcomas is well described in the lit-
erature [15-18]. Cartilage cap thickness is commonly
used as a marker of malignant transformation as malig-
nant transformation typically occurs with cartilage cap
thicknesses greater than 1 - 3 cm [15]. In a study of 101
patients, 34 of which had secondary chondrosarcomas,
Bernard et al. [19] suggested a 2 cm cutoff based on their
described imaging technique to distinguish benign os-
teochondromas from secondary chondrosarcomas. The
sensitivity and specificity of a 2 cm cutoff was 100% and
98% for MRI and 100% and 95% for CT, which are en-
couraging results and which arguably may support this
method of evaluation as the current standard of care [19].
Limitations of our study include a small sample size as
well as a lack of malignant tumors for comparison and
characterization. Even though maximum standardized
uptake values utilizing triple time points were similar in
histologically confirmed benign lesions, we were unable
to make a similar conclusion for low or high-grade
chondrosarcomas, which are inherently more metaboli-
cally active. In addition, the natural history of osteo-
chondromas and their malignant transformation rate is
quite rare, making it difficult to evaluate the use of PET
scan to differentiate benign osteochondroma from chon-
drosarcoma at a single institution.
In conclusion, our preliminary study demonstrated that
maximum standardized uptake values utilizing triple
time point FDG PET for histology confirmed osteochon-
dromas showed no difference to previously published
values utilizing single or dual time point protocols. The
clinical utility of triple time point protocol based on the
half-life of FDG in chondrosarcomas, which are inher-
ently more metabolically active, remains unknown. A
multi-institutional study would provide increased num-
bers and the ability to detect the rare transformation of
osteochondromas to chondrosarcomas. This may ulti-
mately enable investigators to determine reliable and
relevant SUV cutoff points allowing for the distinction of
benign osteochondromas from low-grade chondrosarco-
mas.
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