Utility of positron emission tomography/computed tomography (PET/CT) imaging in the evaluation of sarcomas: A systematic review

Background Sarcomas are a heterogeneous group of malignant tumours with variable clinical outcomes. Their presence in multiple body locations represents significant diagnostic and therapeutic challenges. Positron emission tomography/computed tomography (PET/CT) is an imaging tool that provides semiquantitative measurements of radiotracer concentration in tissue, such as SUVmax (standardised uptake value) and is increasingly used in clinical practice. This systematic review aims to evaluate the utility of PET/CT in sarcoma grading and prognostication, evaluation of treatment response, staging and restaging. Methods: Relevant studies published from January 2003 to August 2017 evaluating the utility of PET/CT in sarcoma grading and prognostication, staging, evaluation of treatment response and restaging were systematically searched for in scientific databases (e.g. PubMed, Medline and Embase) using key terms, including soft tissue sarcoma, osteosarcoma, utility and PET/CT. Additionally, references of identified studies were reviewed. Study quality was assessed by Quality Assessment of Diagnostic Accuracy Studies. Results: A total of 12 prospective studies (level II to III evidence) were included in the review for tumour grading and prognostication. There was a strong correlation between SUV and tumour grade where majority of intermediate/high-grade STS have a significantly higher SUVmax. PET/CT has also shown potential in prognostication where decrease in SUVmax correlated with recurrence-free survival in both osteosarcoma and STS. Furthermore, 8 prospective trials of level II to IV evidence according to Oxford Centre of Evidence-based Medicine (CEBM) demonstrated the use of PET/CT in early identification of patients who will respond to treatment where >= 60% decrease in FDG uptake resulted in sensitivity and specificity of 100% and 71% respectively for assessment of histopathologic response. 11 retrospective trials (level III to IV evidence) reported on the use of PET/CT in staging and restaging with heterogeneous results. Conclusion: Overall, higher quality evidence demonstrated PET/CT to be an important contributor towards sarcoma grading, prognostication and evaluation of treatment response. Larger prospective trials will be helpful to further establish the clinical value of PET/CT in sarcoma staging and restaging.