The role of 18F-FDG PET in minimizing variability in gross tumor volume delineation of soft tissue sarcomas.

BACKGROUND: Accurate gross tumor volume (GTV) delineation is a critical step in radiation therapy treatment planning. However, it is reader dependent and thus susceptible to intra- and inter-reader variability. GTV delineation of soft tissue sarcoma (STS) often relies on CT and MR images. PURPOSE: This study investigates the potential role of 18F-FDG PET in reducing intra- and inter-reader variability thereby improving reproducibility of GTV delineation in STS, without incurring additional costs or radiation exposure. MATERIALS AND METHODS: Three readers performed independent GTV delineation of 61 patients with STS using first CT and MR followed by CT, MR, and 18F-FDG PET images. Each reader performed a total of six delineation trials, three trials per imaging modality group. Dice Similarity Coefficient (DSC) score and Hausdorff distance (HD) were used to assess both intra- and inter-reader variability using generated simultaneous truth and performance level estimation (STAPLE) GTVs as ground truth. Statistical analysis was performed using a Wilcoxon signed-ranked test. RESULTS: There was a statistically significant decrease in both intra- and inter-reader variability in GTV delineation using CT, MR 18F-FDG PET images vs. CT and MR images. This was translated by an increase in the DSC score and a decrease in the HD for GTVs drawn from CT, MR and 18F-FDG PET images vs. GTVs drawn from CT and MR for all readers and across all three trials. CONCLUSION: Incorporation of 18F-FDG PET into CT and MR images decreased intra- and inter-reader variability and subsequently increased reproducibility of GTV delineation in STS.

Management of acral myxoinflammatory fibroblastic sarcoma.

BACKGROUND: Acral myxoinflammatory fibroblastic sarcoma (AMFS) is a rare, low-grade sarcoma that commonly affects the distal extremities. From the published cases, therapy for AMFS to date has been comprised of excision or amputation, with limited use of radiotherapy (RT) or chemotherapy. In this report, the outcome of 17 patients with AMFS treated at the study institution was reported. METHODS: A retrospective review of all cases of AMFS identified in the Sarcoma Database in the Department of Radiation Oncology at the study institution was conducted. Treatment records and data from follow-up visits of patients were reviewed. RESULTS: Seventeen patients were identified. All the patients underwent surgical resection (15 excisions and 2 amputations). Positive surgical margins after excisions were noted in 5 patients and were widely positive in 1 patient. Of the 17 patients, 14 patients received some form of RT. The average total dose was 56.4 Gray (Gy). Eight patients received preoperative RT alone, 5 patients received preoperative RT and postoperative RT, and 1 patient received preoperative RT and intraoperative RT. Median follow-up was 24.5 months. One patient presented with recurrent disease and was treated with resection, and both pre- and postoperative RT. He was free of disease 23 months after his last treatment. No local recurrence was noted in the remaining patients. Of the 14 patients undergoing preoperative RT, complete pathologic necrosis or no tumor was noted in 1 of the patients. No metastatic disease was observed in any of the patients. There was no significant radiation toxicity observed in any of the patients. CONCLUSIONS: Data were consistent with local control of distal extremity sarcomas with resection and RT, suggesting that limb-sparing surgery with this treatment combination is an appropriate option in the limb-sparing control of patients with AMFS, even those with positive surgical margins.