Initial Report of Boswellia Serrata for Management of Cerebral Radiation Necrosis after Stereotactic Radiosurgery for Brain Metastases.

PURPOSE/OBJECTIVE(S): Radiation necrosis (RN) is a concerning late toxicity after radiation therapy (RT) for brain metastases. Oral corticosteroids are the mainstay of management; however, they are not optimal for long-term use given multiple side effects and drug interactions, particularly with the emergence of immunotherapy for several cancers. Boswellia serrata (BS) is an over-the-counter supplement used for its anti-inflammatory properties and has been recently shown to reduce cerebral edema after brain RT. We evaluated the response rates with BS in a series of patients with brain metastases treated with stereotactic radiosurgery (SRS) who developed RN.

MATERIALS/METHODS: We included patients who developed RN after SRS for brain metastases at our institution from 2020-2022 and were treated with BS. Patients were prescribed over the counter BS 4.2-4.5g daily in divided doses. Follow-up MRI imaging was obtained every 2-3 months after starting BS. Response was assessed using Response Assessment in Neuro-Oncology (RANO) criteria. Primary endpoint was ≥25% decrease in edema volume on T2-FLAIR MRI from baseline. Patients were censored if they had tumor progression or repeat RT to necrotic area, or death. Kaplan-Meier curves were used for survival estimates.

RESULTS: A total of 50 patients received BS for Grade 1-3 CTCAE v5.0 RN (G1 = 11, G2 = 36, and G3 = 3). Median age was 62.8 years (range 36.9 - 50) and median RT dose was 24 Gy in 3 fractions. Median time to RN after SRS was 10 months(m). Median follow-up after starting BS was 6m and 40 patients had at least 1 follow up MRI available to evaluate response. The best response was complete response (CR) in 15% patients and partial response (PR) in 40% while 35% had stable disease (SD) and 10% had progressive disease. Median time to CR was 9m (6-12m) and PR was 6m (3-12m). Percentage of patients who had any response (CR or PR) at 3, 6, 9 and 12 months was 25%, 60%, 43% and 50%, respectively. 56% patients had symptomatic RN, of which 35.7% had improvement in symptoms with BS alone, while 64% required steroid use. Overall, median duration of response in patients with CR, PR or SD was 7.5m(range 2-31m). Salvage treatment for RN was steroids (33), surgery (4), Bevacizumab (5) or hyperbaric oxygen therapy (1). No patients had any CTCAE grade 3 or higher toxicities. 3 patients (6%) had any side-effects all of whom had Grade 1-2 gastrointestinal intolerance or diarrhea. 2 patients stopped treatment due to enrolment on an immunotherapy clinical trial. Overall, 39 patients remained on BS at last follow-up or death.

CONCLUSION: We observed >50% response rates with use of BS in our cohort of patients with Grade 1-3 RN after SRS. More than 1/3rd patients with symptomatic RN were able to avoid long-term steroid use. BS is an easily available over-the-counter drug that appears to be a safe and promising treatment option for RN, and can potentially decrease steroid dependence in these patients, reducing the risk of several side-effects. Further prospective studies to compare Boswellia with placebo is warranted.