Marcelo Kuperman Benveniste MD, Presenter: Nothing to Disclose

Cesar Moran MD, Abstract Co-Author: Nothing to Disclose

Osama R. Mawlawi PhD, Abstract Co-Author: Nothing to Disclose

Patricia Sue Fox MS, Abstract Co-Author: Nothing to Disclose

Stephen G. Swisher MD, Abstract Co-Author: Consultant, GlaxoSmithKline plc

Edith Michelle Marom MD, Abstract Co-Author: Nothing to Disclose

Metabolic tumor volume assessment using positron-emission tomography (PET)–CT has a role for monitoring response to therapy in oncologic patients. Assessment of tumor volume above a specific SUV threshold has a potential promise to distinguish between early (Stage I and II) and advanced thymoma (stage III and IV) as well as high risk thymoma (Type B3) from low risk according to WHO Classification. It is important to differentiate these neoplasms before surgery, as patients with a worst histological type or locally advanced tumors require neoadjuvant chemotherapy that enables effective resection. Thus, tumor volumetric assessment could be used to direct those patients. This study assessed whether the volumetric standardized uptake value (SUV) measurements can predict advanced thymoma and whether it can separate type B3 thymoma from low risk thymoma.

We retrospectively reviewed FDG positron emission tomography (PET)-CT scans of 51 consecutive newly diagnosed patients with thymic epithelial malignancy. PET-CT findings documented were focal FDG activity: SUVbwmax, SUVbwmean, SUVbwpeak and total body volumetric standardized uptake value (SUV) measurements. These were correlated with Masaoka-Koga staging and WHO classification. Wilcoxon rank-sum tests were used to assess association between SUV and pathological stage, cancer type, and classification.

Among the study patients, 37 had thymoma, 12 thymic carcinoma, and 2 thymic carcinoid. Higher total tumor volume above SUV 3.5 was seen in patients with type B3 thymoma than in those with type A, AB, B1, or B2 thymoma (p=0.04). Total tumor volume above SUV 3.5 was higher in patients with advanced stage than in early stage disease (p=0.0008). Additionally, patients with thymic carcinoma or carcinoid demonstrated a higher total tumor volume above SUV 3.5 than in those with thymoma (p=0.02).

Metabolic tumor volume assessment is helpful in distinguishing early from advanced stage thymoma, low-risk thymoma from more aggressive thymoma (type B3) and thymic carcinoma/carcinoid tumors from thymoma.

Metabolic tumor volume assessment has a potential to differentiate between early and invasive thymomas and help in clinical decisions.

Benveniste, M, Moran, C, Mawlawi, O, Fox, P, Swisher, S, Marom, E, Volumetric FDG PET-CT in the Preoperative Assessment of Patients with Thymic Epithelial Malignancies.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13013101.html