Theranostic implications of molecular imaging phenotype of well-differentiated pulmonary carcinoid based on 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT.
Published on Jan 1, 2021in European Journal of Nuclear Medicine and Molecular Imaging9.236
· DOI :10.1007/S00259-020-04915-7
This study aimed to analyse the molecular imaging (MI) phenotype of typical carcinoid (TC) and atypical carcinoid (AC) by 68Ga-DOTATATE (GaTATE) and 18F-FDG (FDG) PET/CT with the emphasis on its potential theranostic implications for peptide receptor radionuclide therapy (PRRT). Retrospective review of patients with biopsy-proven TC or AC undergoing both GaTATE and FDG PET/CT at presentation. Based on correlative CT or MRI, positive lesions on either scan were defined by uptake above liver parenchyma. Per patient MI phenotypic pattern was classified as score 1, if all lesions were negative on both scans; score 2, if all were GaTATE positive/FDG negative; score 3, if all lesions were GaTATE positive but some or all were also FDG positive and score 4, if there were any GaTATE negative/FDG positive lesions. Scores 1 and 4 were deemed unsuitable for PRRT. Of 56 patients (median age 66.5 years, 32 female), 22 had TC, and 34 had AC. Distant metastases were seen in 32% of TC and 94% of AC. At a median follow-up of 37 months for TC and 38 months for AC, 100% and 63% were alive, respectively. Median OS for AC was 56 months (95% CI 43, not reached [NR]), and TC was NR. On inter-patient dual-tracer analysis, scores 1, 2, 3 and 4 were 23%, 18%, 36% and 23% in TC and 3%, 15%, 32% and 50% in AC, respectively. In 16 patients (score 2, N = 3; score 3, N = 12; score 4, N = 1) who were treated with PRRT, disease control rate at 3 months and OS were, 85% and 54.6 months (95% CI 44–70), respectively. TC and AC showed a wide inter-patient phenotypic heterogeneity on GaTATE and FDG with around half of patients (46% TC and 53% AC) having an unsuitable phenotype for PRRT. Dual-tracer MI phenotype can be used to select the most suitable patients for PRRT.