Abstract 1183P
Background
To investigate safety, tolerability and best sequence treatment in patients subjected to Peptide Radio-Receptor Therapy (PRRT) and Selective Internal Radiation Therapy (SIRT) for metastatic liver-dominant GEPNETs.
Methods
Ninety-eight patients treated with PRRT and SIRT in our Institute, from 2012 to y2016, were retrospectively reviewed. Treatment toxicity was assessed according to CTCAE v5.0. Dosimetric analysis of dose administered by SIRT was estimated by 99mTc-MAA-angioscintigraphy. Treatment response was evaluated by RECIST1.1 criteria. Disease Control Rate (DCR), PFS and OS were calculated (Kaplan-Meier).
Results
Eight patients (6 males, 2 females, mean age 52 years, range 37-61) who underwent both SIRT and PRRT were identified. All the patients had G1-G2 GEPNET hystological diagnosis with unresectable liver- dominant disease. Five patients (Group 1) underwent SIRT before PRRT, three (Group 2) received PRRT followed by SIRT. In both groups the median interval between the last administration of first treatment (PRRT or SIRT) and the first administration of the second one was 18 months. Both therapeutic combinations showed limited toxicity, without delayed G3-G4 adverse events. The best SIRT response was observed at 3-months follow-up both in Group2 (DCR 66.7%) and in Group1 (DCR 60%). An excellent PRRT response (DCR 100%) was observed in Group2 at 3-months follow-up and was maintained at least for 12 months. Similarly, the DCR in Group1 was 100% at 3- month follow-up but decreased until 40% 12 months after PRRT. Dosimetric data were available for 7 of 13 SIRT procedures showing high cumulative dose to target lesions and low dose to healthy liver. Median PFS was briefer in Group1 than in Group 2 (26 vs 45 months) but Kaplan-Meier analysis fails to achieve statistical significance (95% CI 17-60, P value: 0.655). OS curves were significantly different (95% CI 14-59, P value: 0.024), with a median OS of 29 months in Group1 compared to 55 months in Group2.
Conclusions
Therapeutic combination of PRRT and SIRT represented a reliable approach in terms of safety and tolerability in liver-dominant GEPNETs. The preliminary results are favourable to opt for PRRT before SIRT, in the sequential treatment decision.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.