2847 - Toxicity Outcomes Following Spine Stereotactic Body Radiotherapy and Bevacizumab

Purpose/Objective(s):   Multiple reports have described increased rates of severe gastrointestinal (GI) toxicity when bevacizumab is delivered concurrently or near the time of radiotherapy, raising concern regarding the safety of combining these treatments. Although our institution aims for a prolonged interval between infusions and radiation, this is not always feasible and supporting clinical data remain limited. We report our experience delivering spine stereotactic body radiotherapy (SBRT) with concurrent or near-concurrent bevacizumab.

Materials/Methods:   We retrospectively reviewed patients treated with spine SBRT between 2011 and 2025 who received bevacizumab within 60 days of radiation. Patient, treatment, and toxicity data were collected. Toxicities were graded according to CTCAE v5.0. The primary endpoint was grade =3 GI toxicity. Descriptive statistics were used to summarize outcomes. 

Results:   Seventeen patients underwent spine SBRT while receiving bevacizumab in the peri-radiotherapy period and had median follow up of 242 days. The median interval between bevacizumab exposure and SBRT was 32 days (16-45) pre-RT and 14.5 days (6-28) post RT. Bevacizumab was administered <2 weeks from SBRT in 63% of patients and <1 week in 24% (Table1). No grade =3 GI toxicities were observed. Dosimetric data are in Table 1. Grade =3 events included vertebral compression fracture (n=2), wound-related complications (n=2), and fatigue (n=1). The wound-related events consisted of osteonecrosis of the jaw for a patient getting cervical spine RT at the 13Gy₂ isodose line who received a concurrent bisphosphonate and a nonhealing sacral wound for a patient getting sacral spine RT at the 51Gy₂ isodose line following vertebroplasty at this level. These occurred 63 and 342 days post-treatment, respectively. Two patients experienced grade 2 esophagitis. No treatment-related hospitalizations occurred. 

Conclusion:   In this cohort of patients with the majority receiving concurrent or near-concurrent bevacizumab and spine SBRT, no grade =3 GI toxicities were observed. These findings suggest that bevacizumab-associated GI complications may be uncommon in spine SBRT when visceral organs are appropriately spared, even without a washout period. While continued caution and prospective validation are warranted, this experience provides clinically relevant reassurance regarding the GI safety of spine SBRT when bevacizumab washout, though standard, is not feasible.