Predictors of outcome in patients treated with peptide radio-labelled receptor target therapy (PRRT).

Abstract

4090 Background: The efficacy of peptide-radiolabelled receptor targeted therapy (PRRT) in patients with well differentiated neuroendocrine tumours has been demonstrated in Phase II and Phase III studies. The recently completed phase IV NETTER-01 demonstrated disease stabilisation or partial response in approximately 80% of patients. However, more studies are needed to identify predictors of PRRT response. We sought to investigate the clinic-pathological characteristics in patients that had radiological progression or death within 12 months of completion of treatment with PRRT. Methods: We performed a retrospective analysis of all patients who had PRRT from 2011-2016. Patient with at least one year of follow-up data from the last treatment dose were included. Patients with evidence of radiological progression within one year of finishing treatment (Group 1) were compared to a similar group with disease stabilisation/response (Group 2)that were matched for age, grade, primary and distribution of metastases. The indication for PRRT was defined as either small volume progression ( < 20%) or progression by RECIST. Results: 307 patients underwent PRRT with Lu-177 or Y-90 DOTATATE during this period. 66 patients in Group 1 were compared to 64 patients in Group 2. There was a significant difference in median overall survival, Group 1 = 21 months compared to Group 2 = 35 months, (p < 0.002). A significantly higher proportion of patients in group 1 had more than 50% liver volume (p < 0.0001). Mean CgA was significantly higher in Group 1, 1250 pg/ml vs 608 pg/ml in Group 2 ( p < 0.03). 18 patients in Group 2 had small volume progression prior to treatment commencement compared to 6 in Group 1 (p < 0.003). Conclusions: Radiological progression within 12 months of completion of PRRT is associated with a worse outcome in terms of OS. Patients with greater liver involvement and highest CgA levels are more likely to progress within 12 months of treatment completion. Earlier treatment with PRRT in patients with radiological progression not meeting RECIST criteria may need to be conisdered. There may be a greater survival benefit if PRRT is given prior to the development of large volume disease.