Survival and relapse patterns in patients of cranial vs extra-cranial oligometastases treated with stereotactic radiosurgery/stereotactic body radiation therapy and systemic therapy

Objectives: To evaluate the outcome of patients with cranial (C) and extra-cranial (EC) oligometastases treated with stereotactic radiosurgery (SRS)/stereotactic body radiotherapy (SBRT) and standard of care systemic therapy.

Methods: During the period 2018-2022, patients who received SBRT or SRS for oligometastases (≤5 lesions) in addition to systemic therapy were evaluated. PET-CT was done to categorize them as C or EC oligometastases. Local control, distant progression, progression-free survival (PFS), overall survival (OS), and toxicity of the treatment were recorded.

Results: 43 patients received SBRT/SRS to 88 oligometastatic lesions. Eighteen patients had C metastases, 23 had EC metastases and 2 patients had both. 40/43 patients had received systemic therapy. At a median follow-up of 13 months, median PFS was 14 months and 1 and 2 years OS was 83.2% and 67.4%. Local control with SRS was 92.8% and with SBRT was 86.3%. Distant failure in C vs EC oligometastases was seen in 12/14 vs 7/20 patients (P = 0.03). Median PFS was 30 months for EC and 6 months for C oligometastases (P = 0.003). 1 and 2 years OS was 89.6% and 82.7% for EC and 77.6% and 48.5% for C oligometastases (P = 0.21). One patient had grade 3 and 3 patients had grade 1 toxicity.

Conclusions: SRS and SBRT yielded high rates of local control with low toxicity. Compared to EC, patients with C oligometastases had higher distant relapses, poorer PFS, and a trend towards worse survival. More studies with separate enrolment of patients with C and EC oligometastases are needed.

Advances in knowledge: Outcome of patients with C oligometastases is poorer than EC metastases and hence the studies should be separately done in these 2 groups to assess the benefit of SRS/SBRT.