ESTRO 2024 - Abstract Book

S1940

Clinical - Mixed sites, palliation

ESTRO 2024

The median age of the patients included was 72 years (48-88), with a gender distribution of 67,5% male and 32.3% female.

The mean radiotherapy dose administered was 44,98Gy (20-60Gy), and the mean dose per fraction was 9,56Gy (5 20). With a medium Biological Effective Dose (BED) of 84,7Gy (48-151).

The most common primary tumor localization was lung in 12 patients (19,4%). Other locations in the study were: prostate in 13 patients (21%), colon in 9 patients (14,5%), breast in 6 patients (9,7%) and 22 patients had other primaries (25,5%). The percentage of patients who had 1 to 2 metastases was 91.9%, while those who had 4 or more was 4.8%. The most common localization was lung (53,9%), bone (21,3%), lymph node (12,4%), vertebral (9%), adrenal gland (2,2%) and hepatic (1,1%). With a mean follow up of 34 months (95% IC 30-38). The Overall Survival (OS) at 42 moths was 47% (95% IC). OS is influenced by tumor histology, the stage at diagnosis, and the number of metastases. Primary prostatic tumors exhibit higher survival rates (p=0,01), whereas rectal tumors demonstrate the lowest survival rates (p=0,21).

PFS at 18 and 42 months was 52% and 39,5% respectively (95% IC 11-31).

Local control (LC) at 18 and 42 months was 88% and 70% respectively, with a mean LC of 34 (95% IC 26,9-42,6). The Cox-regression of LC was influenced by the localization, number of metastases, stage at diagnosis, total dose, BED and first control radiological response. Lung metastases have the worst LC (p=0,03), the response in radiological control increases LC (p=0,032).

In terms of progression the distribution was 3,3% local (of them, only one was in the radiotherapy field) and 39,3% were distance relapse.

Conclusion:

In conclusion based on our experience with a mean follow up of 34 months, we observed an OS benefit particularly in patients with primary prostatic tumors and in those with lower stages at diagnosis. With a significative improvement in local control.

Although the number of patients included in our cohort is not very high, we have observed a benefit in terms of OS and local control without significant toxicity added.

This allows us to continue recommending a radical metastases approach with stereotactic radiotherapy (SABR) in our regular clinical practice, always with the clinical support of a multidisciplinary team.

Keywords: oligometastatic, SBRT,

References:

Robert Olson, Lindsay Mathews et al. Stereotactic ablative radiotherapy for the comprehensive treatment of 4-10 oligometastatic tumor (SABR-COMET 3): study protocol for a randomized phase III trial. BMC Cancer. 2020; 20:380.