Tumor volumes and SUV of different organs from ⁶⁸Ga-DOTATOC PET/CT scans to predict survival of patients with NET after PRRT with ¹⁷⁷Lu-DOTATATE

Ziel/Aim So far, few studies have specifically investigated volumetric parameters in regard to their prognostic impact on neuroendocrine tumors (NET). In this study the total tumor load (TTL), SUV_mean and SUV_max, as well as the TL of specific organ systems of NET patients were segmented from Ga-68-DOTATOC PET/CT and correlated to overall survival (OS) after PRRT.

Methodik/Methods From 81 patients treated with PRRT tumor volumes were generated via a standardized semi-automatic delineation procedure (PARS; v3.0 Siemens). Segmentation of lesions above SUV_peak 4 was performed with delineation at 42% SUV_peak and lesions<0,5mL were excluded. Total tumor volumes and tumor volumes from liver, bones, lymph-nodes, and abdominal TL as well as SUV_mean/max were analyzed by Cox regression.

Ergebnisse/Results In addition to automatic segmentation, manual segmentation had to be performed for 2.5% of all lesions. Median OS was 50.7 months, median TTL was 201.27mL, median liver TL was 165.34mL, median abdominal TL was 12.93mL. The abd. TL was prognostically unfavorable with a Hazard Ratio (HR) of 1.014 (p=0.016) in the univariate cox regression, whereas TTL, liver TL, bone TL and lymph-node TL had an HR of close to 1 with non-significant p values. Analysis of follow up showed that tumor reduction of liver TL had a HR of 0.87 (p=0.015) and the reduction of lymph node TL had a HR of 0.93 (p=0.015) in the univariate cox regression. The TTL reduction had a HR of 0.57 (p=0.078) in the univariate cox regression. The multivariate cox regression of TTL, abd. TL, sex, functionality of tumor, ki67 yielded significant results for the abd. TL (p=0.00013, HR=1.03), sex (p=0.04, HR=0.3) and ki67 (p=0.03, HR=1.124).

Schlussfolgerungen/Conclusions We show that organ-specific tumor segmentation from PET/CTs results in prognostic parameters in NET patients. In particular, abd. TL was associated with a shorter OS. The reduction of liver TL had a positive prognostic effect on OS, which supports the use of ablative procedures reducing liver tumor mass in liver dominant disease.