Frameless stereotactic radiosurgery in the management of brain metastases: long-term oncologic and toxicity outcomes.

OBJECTIVE

Gamma Knife radiosurgery (GKRS) is a widely accepted treatment modality for brain metastases and has historically relied on pin-based frame fixation, with a frameless option introduced in recent years. Previous studies suggest similar local control and overall survival between frameless and frame-based GKRS, but data on long-term outcomes remain limited. In this study, we sought to evaluate outcomes of single-fraction frameless GKRS for patients treated at our institution between 2018 and 2024.

METHODS

We retrospectively reviewed the medical records of patients treated with single-fraction frameless GKRS for brain metastases. Patient characteristics, treatment parameters, local control, freedom from distant recurrence, and overall survival were evaluated, as well as toxicity outcomes such as radiation necrosis and new-onset seizures.

RESULTS

Our cohort included 140 patients with a total of 362 brain metastases. Primary tumor types included non-small cell lung (32%), breast (21%), melanoma (16%), and gastrointestinal (9%). Median marginal dose was 20 Gy, with mean target volume of 0.14 cc (0.04-0.56). Median clinical follow-up time was 2.4 years. At 1- and 2-years post-treatment, local control was 98% (95% CI, 96%-100%) and 97% (95% CI, 94%-99%), respectively. Median overall survival was 2.5 years (95% CI, 1.992-4.271). One patient (0.7%) had symptomatic radiation necrosis following treatment.

CONCLUSIONS

In this single-institutional experience, frameless GKRS demonstrated excellent oncologic outcomes, adding to the growing body of literature that frameless-based radiosurgical techniques do not compromise locoregional control. To our knowledge, this is the largest single-institution frameless GKRS cohort reported to date.