Promises and challenges of positron emission tomography for assessment of sarcoma in daily clinical practice

Abstract

A correct histological diagnosis, careful staging and detection of tumour response to treatment are all crucial in the management of sarcomas. Imaging is important in all of these stages. Sarcomas have distinct biological and treatment-related features posing challenges for imaging. For example, size measurements may not adequately reflect response rates. Techniques which can measure tissue function rather than generate merely anatomical data such as positron emission tomography (PET) are rapidly gaining interest. We discuss the importance of imaging in different stages of patient management, emphasising the unique characteristics of sarcoma. Furthermore, we discuss the potential of PET for the various indications, focussing on therapy evaluation.

Figure 1

Patient with liver metastasis from gastric GIST. Top, PET; middle, contrast-enhanced diagnostic CT; bottom, fused images. After 18 days of imatinib there was a complete metabolic response on PET, while CT showed stable disease according to RECIST (−15%) and partial response according to Choi et al.^[32].

Figure 2

(a) A patient with Ewing's sarcoma of the left femur. Top, PET; middle, low-dose CT; bottom, fused images. After two cycles of polychemotherapy PET showed (good) partial metabolic response while MRI showed stable disease according to RECIST (−16%). The resection sample showed only microscopic residue of viable tumour (> 90% necrosis) and therefore correlated well with PET. (b) Axial contrast-enhanced spin echo T1-weighted MRI image with fat-saturation acquired on the same day.