Sensitivity and specificity of FDG-PET in detecting abdominopelvic disease in desmoplastic small round cell tumor
Shakeel Modak, Manjusha Namuduri, Anna Camp, Emily K. Slotkin, Megan Fiasconaro, Audrey Mauguen, Michael LaQuaglia, Neeta Pandit-TaskarPurpose
Desmoplastic Small Round Cell Tumor (DSRCT), a rare sarcoma, is characterized by disseminated peritoneal disease often with innumerable implants which are difficult to image. Patients are typically treated with neoadjuvant chemotherapy followed by attempted gross total resection. FDG-PET has been used to monitor effects of chemotherapy but limited data exist regarding its sensitivity and specificity for DSRCT after neoadjuvant chemotherapy.
Methods
In this retrospective study, we correlated findings on FDG-PET scans post-neoadjuvant chemotherapy, before definitive surgery, with operative findings and histopathology. Statistical analyses were performed using generalized estimating equations logistic models for correlation of lesions. The clustered Wilcoxon rank sum test was used to assess differences in characteristics on PET.
Results
Twenty-seven patients were included in this analysis. All had at least 1 PET-positive lesion, and 26/27 (96%) had at least 1 DSRCT lesion on histopathology. Of 360 resected lesions, 273 were involved with DSRCT. At the lesional level, sensitivity of PET was 64% (176/273 lesions were positive on PET and histopathology), and specificity was 76% (66/87 lesions uninvolved on histopathology were PET-negative). Positive and negative predictive values were 89% (95%CI 79-95%) and 40% (95%CI 30-52%), respectively. Lesion size at resection correlated with PET positivity (p=0.003) but size on PET-CT did not (p=0.25), nor did amount of necrosis (p=0.35).
Conclusion
At the patient level, pre-operative FDG-PET was highly sensitive for DSRCT. However, post-neoadjuvant chemotherapy, the utility of PET at the lesional level for surgical planning was limited.