MR-guided stereotactic radiotherapy of infra-diaphragmatic oligometastases: Evaluation of toxicity and dosimetric parameters

Radiother Oncol. 2024 Mar:192:110090. doi: 10.1016/j.radonc.2024.110090. Epub 2024 Jan 13.


Background and purpose: The SOFT trial is a prospective, multicenter, phase 2 trial investigating magnetic resonance (MR)-guided stereotactic ablative radiotherapy (SABR) for abdominal, soft tissue metastases in patients with oligometastatic disease (OMD) ( ID NCT04407897). We present the primary endpoint analysis of 1-year treatment-related toxicity (TRAE).

Materials and methods: Patients with up to five oligometastases from non-hematological cancers were eligible for inclusion. A risk-adapted strategy prioritized fixed organs at risk (OAR) constraints over target coverage. Fractionation schemes were 45-67.5 Gy in 3-8 fractions. The primary endpoint was grade ≥ 4 TRAE within 12 months post-SABR. The association between the risk of gastrointestinal (GI) toxicity and clinical and dosimetric parameters was tested using a normal tissue complication probability model.

Results: We included 121 patients with 147 oligometastatic targets, mainly located in the liver (41 %), lymph nodes (35 %), or adrenal glands (14 %). Nearly half of all targets (48 %, n = 71) were within 10 mm of a radiosensitive OAR. No grade 4 or 5 TRAEs, 3.5 % grade 3 TRAEs, and 43.7 % grade 2 TRAEs were reported within the first year of follow-up. We found a significant association between grade ≥ 2 GI toxicity and the parameters GI OAR D0.1cc, D1cc, and D20cc.

Conclusion: In this phase II study of MR-guided SABR of oligometastases in the infra-diaphragmatic region, we found a low incidence of toxicity despite half of the lesions being within 10 mm of a radiosensitive OAR. GI OAR D0.1cc, D1cc, and D20cc were associated with grade ≥ 2 GI toxicity.

Keywords: MR-linac; Oligometastatic disease; Risk-adaption; SABR; SBRT; Stereotactic ablative radiotherapy; Stereotactic body radiotherapy; Toxicity.

Publication types

  • Clinical Trial, Phase II
  • Multicenter Study

MeSH terms

  • Dose Fractionation, Radiation
  • Humans
  • Neoplasms*
  • Prospective Studies
  • Radiosurgery* / adverse effects

Associated data