Semiquantitative assessment of FDG uptake in primary tumours

Abstract

Objective: To semiquantitatively estimate fluorine-18-fluorodeoxyglucose (FDG) uptake in primary lung cancer cells using dynamic and dual-time-point (DTP) positron emission tomography/computed tomography (PET/CT) to obtain a diagnostic index for lymph node (LN) metastasis. Methods: Forty-five patients with lung cancer underwent dynamic and DTP PET/CT examinations. All primary lesions and LN metastases were evaluated pathologically. At each time phase, we assessed the maximum standardised uptake value (SUVmax), metabolic tumour volume (MTV), and total lesion glycolysis (TLG) of the primary tumours. We investigated the relationship between semiquantitative index and the presence of LN metastasis for each case and for all cases satisfying indications for segmentectomy. In cases with LN metastasis, we assessed the SUVmax of pathologically proven metastatic LNs and non-metastatic LNs in each dynamic phase for evaluating temporal change. Results: Among 45 patients, 15 had 17 LN metastasis. SUVmax, MTV, and TLG of primary tumours at each time phase were significantly associated with LN metastasis (p < 0.05). In receiver operating characteristic analysis, dynamic second and third phases showed high diagnostic ability for LN metastasis. The temporal change in SUVmax in the dynamic phase between primary tumours and metastatic LNs were significantly different (p = 0.065). The temporal change in SUVmax was significantly lower in non-metastatic LNs than in primary tumours and metastatic LNs (p < 0.0001). Conclusions: Semiquantitative assessment of FDG uptake in dynamic second and third phases and the assessment of temporal changes in SUVmax on dynamic PET/CT scans were important predictors in diagnosing LN metastasis