Quantitative SSTR-PET/CT: a potential tool for predicting everolimus response in neuroendoctine tumour patients

Radiol Oncol. 2024 Jun 12;58(3):348-356. doi: 10.2478/raon-2024-0032. eCollection 2024 Sep 1.

Abstract

Background: This study aimed to assess 68Ga-DOTA-TATE (-TOC) PET/CT quantitative parameters in monitoring and predicting everolimus response in neuroendocrine tumor (NET) patients with hepatic metastases (NELM).

Patients and methods: This retrospective analysis included 29 patients with 62 target lesions undergoing everolimus treatment and pre-therapy, and follow-up 68Ga-DOTA-TATE (-TOC) PET/CT scans. Response evaluation utilized progression-free survival (PFS) categorized as responders (R; PFS > 6 months) and non-responders (NR; PFS ≤ 6 months). Lesion size and density, along with maximum and median standardize uptake value (SUV) in target lesions, liver, and spleen were assessed. Tumor-to-spleen (T/S) and tumor-to-liver (T/L) ratios were calculated, including the tumor-to-spleen (T/S) ratio and tumor-to-liver (T/L) ratio (using SUVmax/SUVmax, SUVmax/SUVmean, and SUVmean/SUVmean).

Results: PET/CT scans were acquired 19 days (interquartile range [IQR] 69 days) pre-treatment and 127 days (IQR 74 days) post-starting everolimus. The overall median PFS was 264 days (95% CI: 134-394 days). R exhibited significant decreases in Tmax/Lmax and Tmean/Lmax ratios compared to NR (p = 0.01). In univariate Cox regression, Tmean/Lmax ratio was the sole prognostic parameter associated with PFS (HR 0.5, 95% CI 0.28-0.92, p = 0.03). Percentage changes in T/L and T/S ratios were significant predictors of PFS, with the highest area under curve (AUC) for the percentage change of Tmean/Lmax (AUC = 0.73). An optimal threshold of < 2.5% identified patients with longer PFS (p = 0.003). No other imaging or clinical parameters were predictive of PFS.

Conclusions: This study highlights the potential of quantitative SSTR-PET/CT in predicting and monitoring everolimus response in NET patients. Liver metastasis-to-liver parenchyma ratios outperformed size-based criteria, and Tmean/Lmax ratio may serve as a prognostic marker for PFS, warranting larger cohort investigation.

Keywords: SSTR-PET/CT; everolimus; neuroendocrine tumors; response.

MeSH terms

  • Adult
  • Aged
  • Antineoplastic Agents / therapeutic use
  • Everolimus* / administration & dosage
  • Everolimus* / therapeutic use
  • Female
  • Humans
  • Liver Neoplasms* / diagnostic imaging
  • Liver Neoplasms* / drug therapy
  • Liver Neoplasms* / secondary
  • Male
  • Middle Aged
  • Neuroendocrine Tumors* / diagnostic imaging
  • Neuroendocrine Tumors* / drug therapy
  • Neuroendocrine Tumors* / mortality
  • Neuroendocrine Tumors* / pathology
  • Octreotide / analogs & derivatives
  • Octreotide / therapeutic use
  • Organometallic Compounds / therapeutic use
  • Positron Emission Tomography Computed Tomography* / methods
  • Progression-Free Survival
  • Radiopharmaceuticals
  • Receptors, Somatostatin / metabolism
  • Retrospective Studies
  • Treatment Outcome

Substances

  • Everolimus
  • Organometallic Compounds
  • Radiopharmaceuticals
  • Antineoplastic Agents
  • Receptors, Somatostatin
  • Octreotide
  • gallium Ga 68 dotatate