Volume of interest delineation techniques for ¹⁸F-FDG PET-CT scans during neoadjuvant extremity soft tissue sarcoma...

This study explores various volume of interest (VOI) delineation techniques for fluorine-18-fluorodeoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET-CT) scans during neoadjuvant extremity soft tissue sarcoma (ESTS) treatment.

During neoadjuvant treatment, hyperthermic isolated limb perfusion (HILP) and preoperative external beam radiotherapy (EBRT), 11 patients underwent three ¹⁸F-FDG PET-CT scans. The first scan was made prior to the HILP, the second after the HILP but prior to the start of the EBRT, and the third prior to surgical resection. An automatically drawn VOI_auto, a manually drawn VOI_man, and two gradient-based semi-automatically drawn VOIs (VOI_grad and VOI_grad+) were obtained. Maximum standardized uptake value (SUV_max), SUV_peak, SUV_mean, metabolically active tumor volume (MATV), and total lesion glycolysis (TLG) were calculated from each VOI. The correlation and level of agreement between VOI delineation techniques was explored. Lastly, the changes in metabolic tumor activity were related to the histopathologic response. The strongest correlation and an acceptable level of agreement was found between the VOI_man and the VOI_grad+ delineation techniques. A decline (VOI_man) in SUVmax, SUVpeak, SUVmean, TLG, and MATV (all p < 0.05) was found between the three scans. A > 75% decline in TLG between scan 1 and scan 3 possibly identifies histopathologic response.

The VOI_grad+ delineation technique was identified as most reliable considering reproducibility when compared with the other VOI delineation techniques during the multimodality neoadjuvant treatment of locally advanced ESTS. A significant decline in metabolic tumor activity during the treatment was found. TLG deserves further exploration as predictor for histopathologic response after multimodality ESTS treatment.