1168P - Overall survival (OS) and progression-free survival (PFS) in patients with advanced, non-resectable, progressive rectal NET treated with 90Y DOTA-TATE, 177Lu DOTA-TATE and mix of both as systemic radioligand therapy: Real-world data

Background

Retrospective, single-arm, evaluation of the efficacy of different types of radioligand therapy (RLT) including ⁹⁰Y or ¹⁷⁷Lu DOTA-TATE or mix of both in advanced, unresectable progressive rectal NETG1/G2. The primary endpoint: overall survival (OS); secondary local RECIST 1.1 progression-free survival (PFS).

Methods

24 pts with advanced, unresectable, progressive rectal NETG1/G2 prior to RLT. RLT used 90Y; 177Lu DOTA-TATE or mixture of both in different regimens. Disease status and treatment response were evaluated by clinical assessment, PFS based on local RECIST 1.1 assessment and OS during follow-up. Calculation of OS and PFS using standard KM estimator, differences between groups using the Cox-Mantel test.

Results

Mean age 58.8 +/-12.8, male/female ratio 10/14. NETG1=7 and G2=17. Average of 4.5 therapy sessions, range 2 to 9, and 1.5 therapy courses per patient, range 1-3. 8 pts were treated with 90Y, 9 with 177Lu, 7 had mixed 90Y and 177Lu with 50% of each. Median OS for all 61.1 months (IQR 40-100.4). There was a significant difference in mOS between female OS=73.1 (IQR 48.9-114.0) vs. male OS=42.1 (26.5-53.4) (p=0.02), bulky liver disease >25% involvement OS=42.5 (23.9-57.1) vs. less than 25% OS=100.8 (53.5-116.3); p=0.005. No significant difference in mOS including number of therapy courses, age (below or over 58.8, years), BMI (less or over 25.8), presence of bone and other metastases also G1 vs. G2 tumors. Median PFS for all subjects (IQR) 34.7 months (16.8-43.7). Median PFS was only significantly different between bulky liver disease >25% PFS=19.3 months (IQR 14.3-23.4) vs. less than 25% liver involvement PFS=42.0m (25.5-45.0); p=0.04. There was no significant difference in mPFS including: female vs. male; number of therapy sessions, age (below or over 58.8 years), BMI (less or over 25.8), presence of bone and other metastases also G1 vs. G2 tumors.

Conclusions

Patients with advanced rectal NET1/G2 treated with different regimens of RLT do benefit in terms of improvement of OS in groups of female subjects and with low volume liver involvement. In PFS only low volume liver involvement is a predictor of PFS improvement.

Clinical trial identification

Editorial acknowledgement

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.