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Brain metastases (BM) occur in <4% of all tumours from the gastro-intestinal (GI) tract. The incidence is increasing with more effective systemic treatments and prolonged survival. Whilst whole brain radiotherapy (WBRT) plays an integral part in the management, stereotactic radiosurgery (SRS) is an established treatment modality in both the definitive and adjuvant setting. We present our institutional experience of treating BM from GI malignancies with SRS.

We retrospectively analysed data on patients referred for SRS for BM from GI malignancies between June 2015 and October 2021. Medical records and dosimetry data on these patients were reviewed. We obtained data on patient demographics, tumour characteristics and presence of extra-cranial metastases. SRS was planned using the iPlan software and follow-up neuro-imaging evaluating treatment response was reviewed. The Kaplan-Meier method was used to estimate survival times for individual patients from the day SRS was completed to the date of last follow up or death.

A total of 62 patients were referred with BM from GI malignancies. 4 were unfit for SRS, 2 died before SRS could be delivered and 2 declined and were excluded. 37 patients had extra-cranial metastases at time of referral. Thirty-one patients had colorectal cancer, 19 had oesophageal cancer, 2 had gastric cancer, 1 had pancreatic cancer and 1 had gallbladder cancer. 46 patients (85.2%) had histology consistent with adenocarcinoma. A total number of 92 metastases were treated with 85 being de novo metastases. The median age at time of SRS was 65 years (range 34 to 86). The median GTV treated was 4.85cc and the median cumulative GTV was 9.7cc. 38 metastases were treated with a single fraction, 26 with 3 fractions and 28 with 5 fractions. The median single fraction dose used was 20Gy (range 16 to 24Gy), 3 fraction dose was 27Gy (range 24 to 27Gy) and 5 fraction dose was 26.3Gy (range 25 to 30Gy). The most common toxicities documented were fatigue, headaches and memory impairment. LC rate was 74% based on available follow-up neuro-imaging. Distal intracranial relapse was 20%. Forty-four patients (81%) out of the 54 died. Cumulative proportion surviving was 58% (95% CI: 44% to 72%) at 6 months and 33% (95% CI: 20% to 46%) at 1 year. Median overall survival (OS) was 6.7 months.

Survival and intracranial disease control are poor for BM from GI malignancies. Our retrospective analysis shows that SRS is an effective treatment option and results in comparable OS rates as per reported literature. Larger, multicentre prospective studies are required to determine appropriate patient selection, optimal dose and follow-up protocols. Incorporation of SRS into a multimodal treatment approach should be evaluated to obtain better outcomes.