Background / Introduction

Ga-68-DOTATATE PET/CT imaging of Neuro-endocrine tumours has lead to earlier detection and more accurate staging of these difficult-to-diagnose tumours. One of the important advantages offered by PET/CT imaging, is the ability to more accurately quantify areas of abnormal tracer accumulation. The added prognostic value of quantitative parameters such as MTV and TLG has already been demonstrated in other malignancies.

The aim of this study was to assess whether tumour MTV and/or TLG could be linked to Progression Free Survival (PFS) also in patients with NET.

Methodology

To date 150 patients have undergone imaging with Ga-68-DOTATATE PET/CT. Eligible patients were those who have at least completed 4 cycles of PRRT of whom 18 patients consented to participating in this ongoing study. MTV and TLG were determined for the primary tumour and/or metastatic lesions with Osirix MD using a three-dimensional sphere with a volume of 3cm³ and isocontour set at 40% of SUVmax. Progression Free Survival was calculated in months from the first cycle of therapy received until progression was noted on PET/CT. This was compared to the MTV and TLG values obtained.

Results

Patients included 8 males and 10 females with a median age of 58 years (+/-12.1) and ranged from 29 to74. The majority of patients had more than 5 sites of involvement upon presentation and had failed several other forms of therapy prior to PRRT.

The mean PFS was 23.2 months (=/-11.57) and ranged from 4 to 45 months. MTV and TLG of the primary tumour resulted in median values of 30.6 (1.9-85.1) and 600.8 (37.6-3179.7) respectively. Two-way scatter plots demonstrated an association between lower MTV and TLG values and higher PFS.

Conclusion

Preliminary results suggest an inverse association between MTV and TLG with PFS, which requires further validation.