Objective
This study evaluated the utility of 18F-fluorodexoyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) in staging, grading, and prognostication of Stage III and IV soft tissue sarcomas (STSs).
Methods
Forty patients (Median age = 32.5 years; 25 men) with histologically proven STSs, prospectively underwent 18F-FDG-PET/CTs at baseline. Three-dimensional region of interests were drawn encompassing the lesions to calculate standardized uptake values (SUVs) and metabolic tumor volumes (MTVs). After segmentation, Haralick statistical texture analysis was performed. Follow-up was available for 35 patients. Survival at 6 months was 71.4% and at 1 year was 57.1%.
Results
American Joint Committee on Cancer Stage III was seen in 23 and Stage IV in 17 patients. None of the baseline quantitative and semi-quantitative parameters could predict response or progression. Only reduction in SUVmax in interim PET/CT correlated with baseline SUVmax (Spearman’s Rho = 0.533; P = 0.019). Textural parameters namely ‘contrast’ in CT (P = 0.039) and ‘difference entropy’ in PET/CT (P = 0.051) could differentiate intermediate from high-grade lesions, with corresponding area under curves being 0.736 (0.533–0.889) and 0.700 (0.518–0.882). M1 disease [Hazard ratio (HR): 3.184 (1.179–8.595); P = 0.022], absence of surgical treatment [HR 0.305 (0.106–0.873), P = 0.027 with surgery], lower MTV/total tumor volume (TTV) [HR: 0.975 (0.953–0.997; P = 0.028] and progressive disease in interim PET/CT [3.483 (0.898–13.515); P = 0.056] were predictors of lower survival in univariate analysis. Only M1 disease was found to be reaching significance in multivariate analysis [HR = 2.683 (0.949–7.580); P = 0.063]. Baseline PET/CT changed management in 12.5% of patients [compared to local-imaging and high-resolution CT chest]; with detection of extra-pulmonary metastases. Though, interim and end of treatment PET/CTs detected more metastatic lesions, management was not impacted.
Conclusion
18F-FDG-PET/CT allows for more accurate M-staging in late-stage STSs, which in turn influences the option of curative surgical resection and thus impacts patient prognosis. Lower baseline MTV/TTV and progression in interim PET/CT are also associated with lower survival. Textural analysis may have a role in noninvasive grading.
A 7-year-old male with a history of blunt trauma to the abdomen and diagnosis of perinephric hematoma in contrast-enhanced computed tomography (CT) presented with increasing peri-nephric collection (after ~1.5 months) in the serial ultrasound examinations. The patient was referred to the department of nuclear medicine for the assessment of this collection as well as renal function. In 99mTc-diethylenetriamine pentaacetate renal scintigraphy, progressively increasing radiotracer activity was noted inferolaterally to the left kidney, separated from the same by a photopenic area. Single-photon emission computed tomography/CT revealed a peri-nephric urinoma in relation to the previously diagnosed hematoma at the lower pole; which was communicating with the pelvi-calyceal system (PCS). Not only did the renal scintigraphy aid in the diagnosis of urinoma but it was also able to show that it was communicating freely with the PCS and that the rest of the renal parenchyma was functioning adequately. This multi-faceted assessment in a single investigation allowed clinicians to opt for the conservative management despite the increasing size of urinoma in the early follow-up.
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