Prognostic Role of 2-[18F]FDG PET/CT Metabolic Volume Parameters in Patients Affected by Differentiated Thyroid Carcinoma with High Thyroglobulin Level, Negative 131I WBS and Positive 2-[18F]-FDG PET/CT

The clinical and prognostic role of 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography (2-[18F]FDG PET/CT) in the study of patients affected by differentiated thyroid carcinoma (DTC) with positive serum thyroglobulin (Tg) level and negative [131I] whole-body scan ([131I]WBS) has already been demonstrated. However, the potential prognostic role of semi-quantitative PET metabolic volume features, such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG), has not yet been clearly investigated. The aim of this retrospective study was to investigate whether the main metabolic PET/CT parameters may predict the prognosis. We retrospectively included 122 patients with a positive 2-[18F]FDG PET/CT for DTC disease after a negative [131I]WBS with Tg > 10 ng/mL. The maximum and mean standardized uptake value (SUVmax and SUVmean), MTV and TLG of the hypermetabolic lesion, total MTV (tMTV) and total TLG (tTLG) were measured for each scan. Progression-free survival (PFS) and overall survival (OS) curves were plotted according to the Kaplan–Meier analysis. After a median follow up of 53 months, relapse/progression of disease occurred in 87 patients and death in 42. The median PFS and OS were 19 months (range 1–132 months) and 46 months (range 1–145 months). tMTV and tTLG were the only independent prognostic factors for OS. No variables were significantly correlated with PFS. The best thresholds derived in our sample were 6.6 cm3 for MTV and 119.4 for TLG. In patients with negative WBS and Tg > 10 ng/mL, 2-[18F]FDG PET/CT metabolic volume parameters (tMTV and tTLG) may help to predict OS.

Renal and Salivary Gland Functions after Three Cycles of PSMA-617 Therapy Every Four Weeks in Patients with Metastatic Castration-Resistant Prostate Cancer

Background: [177Lu]Lu-PSMA-617 radioligand therapy (PSMA-RLT) could affect kidney and salivary gland functions in metastatic castration-resistant prostate cancer (mCRPC) patients. Methods: We retrospectively analyzed clinical, renal, and salivary scintigraphy data and salivary [68Ga]Ga-PSMA-11 ligand PET scan measures such as metabolic volume and SUVmax values of 27 mCRPC men (mean age 71 ± 7 years) before and 4 weeks after receiving three cycles of PSMA-RLT every 4 weeks. Twenty-two patients additionally obtained renal and salivary scintigraphy prior to each cycle. A one-way ANOVA, post-hoc Scheffé test and Cochran’s Q test were applied to assess organ toxicity. Results: In total, 54 PSMA PET scans, 98 kidney, and 98 salivary scintigraphy results were evaluated. There were no significant differences for the ejection fraction, peak time, and residual activity after 5 min for both parotid and submandibular glands prior to each cycle and 4 weeks after the last cycle. Similarly, no significant differences in serum creatinine and renal scintigraphy parameters were observed prior to each cycle and 4 weeks after the last treatment. Despite there being no changes in the metabolic volume of both submandibular glands, SUVmax values dropped significantly (p < 0.05). Conclusion: Results evidenced no alterations in renal function and only minimal impairment of salivary function of mCRPC patients who acquired an intense PSMA-RLT regimen every 4 weeks.

252 HETEROGENEITY OF CLINICAL LYMPH NODE INVOLVEMENT (CN+) IN ESOPHAGEAL CANCER: A PERSPECTIVE BASED ON METABOLIC VOLUME

Esophageal cancer with clinical lymph node involvement (cN+) is a heterogeneous disease. Although the cN+ category is of vital importance, preclinical staging cannot establish the number of positive nodes. In this study, we aimed to measure the heterogeneity of esophageal cancer with cN+ based on metabolic volume. We investigated its influence on the response to neoadjuvant treatment. Methods We retrospectively reviewed the patients received neoadjuvant chemotherapy (nCT) and neoadjuvant chemoradiotherapy (nCRT) followed by esophagectomy during January 2016 and November 2018. All patients had received baseline 18F-FDG PET/CT. All patients were restaged according to the 8th TNM Staging System. We measured the metabolic tumor volume (MTV, cm3) of the whole body (MTVwb) and the primary tumor (MTVp) on the workstation. We also calculated the difference of MTVwb and MTVp (MTVn) and the ratio of MTVwb and MTVp (MTVratio). Logistic regression was used to determine the association between the heterogeneity and the response to neoadjuvant treatment. Results Among the 102 patients enrolled in this study, 54 patients had clinically suspicious lymph nodes in small diameters with lower uptake (MTVn as 0). The median MTVwb, MTVp, and MTVn of the patients were 22.34 (2.09 to 105.24), 19.62 (1.93 to 98.06), and 0 (0 to 89.00), respectively. In nCT and nCRT groups (all patients), 15 (37.5%) and 38 (61.3%) achieved ypN0, respectively. In nCT and nCRT groups (MTVn as 0), 12 (42.9%) and 20 (76.9%) patients achieved ypN0, respectively. Logistic regression revealed that MTVn (0 vs. &gt;0) was independently associated with ypN status in nCRT group (P = 0.035). Conclusion nCRT compared with nCT achieved more effective disease control. In esophageal cancer treated with nCRT, the heterogeneity of cN+ measured by metabolic volume was associated with ypN status. A prospective study was in demand to further validate the findings. Video none