¹⁸F‐fluorodeoxyglucose and ¹¹C‐acetate positron emission tomography are useful modalities for diagnosing the histologic type of thymoma

Abstract

BACKGROUND: The objective of this study was to clarify the usefulness of positron emission tomography (PET) using18F‐fluorodeoxyglucose (FDG) and carbon 11‐labeled acetate (AC) for predicting the histologic types and tumor invasiveness of thymoma in a multicenter study. METHODS: Forty thymomas were examined using both FDG‐PET and AC‐PET before surgery. The histologic types were type A in 1 thymoma, type AB in 12 thymomas, type B1 in 11 thymomas, type B2 in 7 thymomas, type B3 in 6 thymomas, and type C in 3 thymomas. Tumor invasiveness was assessed by pathologic tumor stage and was identified as stage I in 17 tumors, stage II in 17 tumors, stage III in 4 tumors, and stage IV in 2 tumors. FDG and AC uptake was measured as the maximum standard uptake value (SUV). RESULTS: The FDG‐SUV in type C thymomas was significantly higher than that in the other types (A‐B3; P = .001 – P = .048). The AC‐SUV in type A/AB thymomas was significantly higher than that in the other tumor types (B1‐C; P < .001 – P = .002). All 3 type C tumors had an FDG‐SUV ≥6.3, and all 13 type A/AB tumors had an FDG‐SUV <6.3 and an AC‐SUV ≥5.7. All 17 thymomas that had an FDG‐SUV <6.3 and an AC‐SUV <5.7 were type B1, B2, or B3. Neither the FDG‐SUV nor the AC‐SUV differed significantly between the stages I/II tumors and stage III/IV tumors. CONCLUSIONS: Although neither the FDG‐SUV nor the AC‐SUV can predict the invasiveness of thymomas assessed by tumor stage, they are useful for predicting histologic types of thymoma. Thymomas with an FDG‐SUV <6.3 and an AC‐SUV ≥5.7 almost certainly are types A/AB, which is of considerable prognostic and management significance. Cancer 2009. © 2009 American Cancer Society.

18F-FDG PET/CT is Useful for Pretreatment Assessment of the Histopathologic Type of Thymic Epithelial Tumors

“…We used SUVpeak because the SUVmax may vary considerably according to scanner performance, matrix size, slice thickness, scanner diameter and reconstruction methods. Like SUVmax, a hottest point within the tumor was included in a fixed small volume of interest for the prediction of histologic type, because the histologic type of each thymoma is determined by its most malignant component [5]. Therefore, the results of SUVpeak in this study concur with SUVmax.…”

“…Types A and AB generally behave like benign tumors, whereas type B1 is a low-grade malignant tumor, type B2 has a greater degree of malignancy, and type B3 has a poor prognosis, similar to that of thymic carcinoma [5]. Most medullary (WHO A) and mixed histology (WHO AB) tumors appear noninvasive, corresponding to Masaoka stages I and II, whereas cortical (WHO B1, 2 and 3) thymomas appear more invasive and occur more commonly as stage III and IV lesions [1].…”

“…Sung et al [4] reported that 18 F-fluorodeoxyglucose ( 18 F-FDG) PET/CT was useful for differentiating among the subgroups of thymic epithelial tumors and for staging the extent of disease. Shibata et al [5] reported that maximum standardized uptake value (SUVmax) in 18 F-FDG PET and 11 Cacetate PET could be used to predict the histologic type of thymoma. However, still the studies about the usefulness of 18 F-FDG PET for the pretreatment evaluation of thymic epithelial tumor are limited.…”

11C-acetate for positron emission tomography imaging of clinical stage IA lung adenocarcinoma: comparison with 18F-fluorodeoxyglucose for imaging and evaluation of tumor aggressiveness

“…Clinically, 11 C-AC has been widely used as a tracer for evaluating myocardial or cerebral oxidative metabolism [5,6]. Recently, 11 C-AC has also been reported to be a useful PET tracer for detecting slow-growing tumors which cannot be identified by FDG-PET, such as W/D lung adenocarcinoma, W/D hepatocellular carcinoma (HCC), prostate cancer, and thymoma [7][8][9][10][11][12].…”

Positron Emission Tomography/Computed Tomography in Mediastinal Masses

“…Timomayı timik karsinomadan ayırmada SUVmaks'ın optimal eşik değeri çalışmalarda 4.6 ile 6 arası değişmektedir (14). Karşıt sonuçlar olsa da (15,16,17), genel görüş düşük risk timomaları yüksek risk timomalardan ayırmada SUV maks değerinin faydalı olmadığı yönündedir (18,19,20,21,22,23).…”