Dual-time point 18FDG-PET/CT imaging may be useful in assessing local recurrent disease in high grade bone and soft tissue sarcoma

Abstract

BACKGROUND: Sarcomas comprise 1% of malignant tumors in adults but represent a significant diagnostic and therapeutic challenge. Molecular imaging with ¹⁸FDG PET/CT is a powerful modality in oncology. Its use for initial assessment, evaluation of response to therapy and recurrent disease in most tumors is essential for therapeutic decisions. Its indication in sarcomas is still controversial. One of the indications for PET/CT in sarcomas is detection of recurrences. Nowadays magnetic resonance tomography (MRT) has a crucial role in identification of local recurrences in soft tissue and bone sarcoma. ¹⁸FDG-PET/CT may serve as a complementary method. Dual time point imaging (DTPI) has been studied for most tumors as a method for differentiating benign from malignant lesions. There is limited data on DTPI in sarcomas. Therefore we studied prospectively patients with suspected local recurrences in the treated area and used DTPI as a method for differentiating benign from malignant tissue.

The aim of this study was to evaluate the ability of dual-time point PET/CT to enhance sensitivity, specificity, PPV, NPV and accuracy of ¹⁸FDG PET/CT in high grade and low grade sarcomas.

MATERIAL AND METHODS: We conducted a dual-time PET/CT in 15 patients with suspected locally recurrent disease. The delayed scan was conducted on the 120th min in the suspected region. The interpretation of PET/CT was made both upon CT scan and metabolic scans. The percentage change over time per lesion was calculated (%DSUV). The increase in SUVmax with %DSUV > 10% in the late scanning was considered as indicative for malignancy. We assessed the sensitivity, specificity, accuracy, positive and negative predicting value of the interpretation of PET/CT at 60 min and 120 min. All of the patients were followed up for a period of 1–3 years after our examination, either with histologic results, or with an MRT scans.

RESULTS: The received sensitivity, specificity and accuracy of ¹⁸FDG PET/CT interpretation at 120 min in high grade sarcomas were respectively 100%, 80% and 89%. By comparison, in low grade tumors at 120 min scan, these parameters were 50%, 75% and 66%.

CONCLUSION: These preliminary data suggests that dual-time imaging in sarcomas improves sensitivity and accuracy in identification of local recurrent disease in high grade sarcomas and have limited role in low grade sarcomas. Further research is necessary to confirm these results.