18-Fluorine fluorodeoxyglucose positron emission tomography in the pretreatment evaluation of thymic epithelial neoplasms: a metabolic biopsy confirmed by Ki-67 expression

• Published in: European journal of cardio-thoracic surgery 2014-09, Vol.46 (3), p.369-374
• Main Authors: Viti, Andrea, Bertolaccini, Luca, Cavallo, Antonio, Fortunato, Mirella, Bianchi, Andrea, Terzi, Alberto
• Format: Article
• Language: English
• Subjects: Adult; Female; Fluorodeoxyglucose F18; Humans; Ki-67 Antigen - analysis; Ki-67 Antigen - biosynthesis; Male; Middle Aged; Neoplasm Staging - methods; Neoplasms, Glandular and Epithelial - diagnostic imaging; Neoplasms, Glandular and Epithelial - metabolism; Neoplasms, Glandular and Epithelial - pathology; Positron-Emission Tomography - methods; Radiopharmaceuticals; Retrospective Studies; Thymus Neoplasms - diagnostic imaging; Thymus Neoplasms - metabolism; Thymus Neoplasms - pathology; Tomography, X-Ray Computed
• ISSN: 1010-7940; 1873-734X
• DOI: 10.1093/ejcts/ezu030

OBJECTIVES To investigate the usefulness of 18-fluorine fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET–CT) in the pretreatment evaluation of thymic epithelial neoplasms (TENs). We previously demonstrated that the ratio between standardized uptake value of the tumour and aortic arch (SUV T/M) correlates with World Health Organization (WHO) classification. We now focused our evaluation on thymomas only, excluding carcinomas. We also searched for the expression of a pathological biomarker, Ki-67, that gained both diagnostic and prognostic relevance for various solid tumours. Its correlation with SUV T/M and WHO classification was evaluated. METHODS We performed a retrospective dynamic cohort study of data from January 2006 to December 2012, on 23 consecutive patients with pathologically proven TEN, excluding thymic carcinomas, evaluated with PET–CT. For each patient, SUV T/M was calculated. The patients were then categorized, according to WHO classification, into two groups (low-risk: 3 A, 9 AB, 5 B1; high-risk: 5 B2, 1 B3) and Ki-67 labelling index (LI) was defined. We employed the Spearman rank non-linear correlation coefficient (ρ) to estimate the correlations between variables. RESULTS SUV T/M proved to be significantly higher for high-positive Ki-67 samples, indicating a strong correlation between SUV T/M and Ki-67 LI (ρ = 0.8). Furthermore, high Ki-67 LI samples correlate with the higher-risk WHO subgroup (ρ = 0.9). CONCLUSIONS FDG PET–CT can provide a useful tool in the preoperative work-up of TEN, reflecting its proliferation capacity, as described also by the Ki-67 expression. In particular, SUV T/M could provide a ‘metabolic biopsy’ to divide TEN into high-risk and low-risk neoplasms.