ESTRO 2024 - Abstract Book

S1473

Clinical - Lower GI

ESTRO 2024

Three patients remained progression-free after a follow-up of two, four and ten months (Figure 1). Two patients (ID 4 and 5) had systemic progression after eight and twelve months based on new metastatic lesions. In one patient (ID 5) the new lesions were also radiated according to the trial protocol, resulting in an ongoing systemic therapy free interval of 11 months. One patient had progression based on recurrence of a rectum tumor (ID 6) after six months. Median OS has not been reached.

Conclusion:

SBRT in combination with systemic therapy in patients with polymetastatic CRC is feasible and safe. The initial treatment effect of SBRT in combination with systemic therapy seems promising in patients with mCRC. However, because of highly effective systemic therapy, 38% of lesions vanished during systemic treatment resulting in no patient with six or more radiated lesions. In an extended lead-in we will expand our target population by counting the number of malignant lesions after initial systemic therapy instead of before, to assess feasibility and safety in patients with a higher number of irradiated lesions.

Keywords: SBRT, oligometastases, mCRC

References:

1. Palma, D. A. et al. Stereotactic ablative radiotherapy versus standard of care palliative treatment in patients with oligometastatic cancers (SABR-COMET): a randomised, phase 2, open-label trial. Lancet Lond. Engl. 393, 2051– 2058 (2019).

2. Chalkidou, A. et al. Stereotactic ablative body radiotherapy in patients with oligometastatic cancers: a prospective, registry-based, single-arm, observational, evaluation study. Lancet Oncol. 22, 98–106 (2021).

3. Ryu, S. et al. RTOG 0631 Phase II/III Study of Image-Guided Stereotactic Radiosurgery for Localized (1-3) Spine Metastases: Phase II Results. Pract. Radiat. Oncol. 4, 76–81 (2014).