Lactate Dehydrogenase A is Associated with Elevated FDG Metabolism, Radioiodine Non-avidity, and Poor Prognosis in Differentiated Thyroid Cancer.

[RATIONALE AND OBJECTIVES] The role of lactate dehydrogenase A (LDHA) expression in differentiated thyroid cancer (DTC), especially in radioiodine-refractory DTC, remains unclear. The aim of this study was to analyse the relationships and the prognostic value of LDHA, glycolysis, and radioactive iodine (RAI) avidity in DTC.

[METHODS] DTC patients who underwent F-FDG PET/CT and subsequent total thyroidectomy or metastasectomy were enroled. The expression levels of LDHA, glucose transporters (Glut) and Ki67 proteins in tumour tissue were measured using immunohistochemistry. The maximum standardised uptake value (SUVmax), metabolic tumour volume (MTV) and total lesion glycolysis (TLG) of F-FDG PET/CT were measured. A radioiodine whole body scan was used to determine lesion radioiodine avidity.

[RESULTS] 69 patients with DTC were enroled in this study, including 37 women (53.6%) and 32 men (46.4%), with a median age of 52 years (11 to 77 years). Regarding the pathological category, papillary thyroid cancer was documented in 50 patients (72.5%), while follicular and poorly differentiated thyroid cancer were found in 12 patients (17.4%) and seven patients (10.1%), respectively. Distant metastases were observed in 27 (39.1%) patients; 34 (49.3%) were classified as stage I, 16 (23.2%) as stage II, and 3 (4.3%) and 16 (23.2%) patients in stages III and IV, respectively. LDHA expression levels were correlated with Glut3 expression levels (r = 0.395, P = 0.003) and SUVmax (r = 0.408, P = 0.002). The median LDHA expression and lesion SUVmax of the RAI avidity group were lower than those of the non-RAI avidity group (200 vs. 285, P = 0.036; 3.06 vs. 8.38, P = 0.038, respectively). Elevated SUVmax (P = 0.004), MTV (P = 0.014), TLG (P = 0.001) and LDHA expression (P = 0.048) led to shorter time to progression (TTP); Cox regression analysis revealed that TLG (HR: 4.773, P = 0.047) was an independent prognostic factor of TTP.

[CONCLUSION] Elevated LDHA is correlated with increased glucose metabolism, decreased radioiodine avidity, and accelerated disease progression. Moreover, F-FDG PET/CT acting as "in vivo pathology" is an excellent predictor of DTC prognosis.