ESTRO 2024 - Abstract Book

S1853

Clinical - Mixed sites, palliation

ESTRO 2024

AC, n=32) lived for 7 (range 1-49) months. OS differences in Kaplan-Meier analyses were not statistically significant but showed a trend towards longer OS in patients with AR or AC, p=0.063 using log-rank test. Two-year OS for patients with AR or AC was 40.6%; [95%CI 0.2956; 0.558], for patients with no abscopal benefit 24.4% [95%CI 0.1171; 0.509]. Median PFS for all patients was 5.5 (range 0-57) months. Patients with complete AR showed a median PFS of 9 (range 0-57) months and with AC 7 (range 1-46) months, whereas patients with AP or no abscopal benefit had a median PFS of 3 (range 0-49) months. Kaplan-Meier analyses showed a significantly longer PFS for patients with abscopal benefits (AR, AC) vs. patients without abscopal benefits using log-rank test (p=0.010), see Figure 2 .

Figure 2 shows the Kaplan- Meier curve for PFS of all patients with ≥1 AR and AC compared to patients without abscopal benefit (AP, no AR, no AC), p=0.010 by log-rank test.

Conclusion:

In this large multi-centre analysis, we could demonstrate that RT induces AbE in more than a third of metastatic tumour patients experiencing progression under ongoing ICI. Importantly, patients with abscopal response and abscopal control demonstrated longer overall and progression-free survival, showing the oncological value of RT-ICI combinations in this patient population. The establishment of suitable RT-ICI schemes could improve outcomes for a prognostically unfavourable patient population, advancing personalised cancer therapy.

Keywords: Abscopal effects, PD1/PDL1, multicentre study