Fractionated Stereotactic Radiotherapy with Helical Tomotherapy for Brain Metastases: A Mono-Institutional Experience

Background: The present study reports on the outcomes of our mono-institutional experience of Helical Tomotherapy (HT)-based SRT for brain metastases. The use of this linac is less frequently reported for this kind of treatment. Methods: This retrospective study displays a series of patients treated with HT-SRT. The eligibility of using SRT for brain metastases was defined by a Karnofsky performance status of >70, a life expectancy of >6 months, and controlled extra-cranial disease; no SRT was allowed in the case of a number of brain metastases larger than 10. All the cases were discussed by a multidisciplinary board. Toxicity assessments were performed based on CTCAE v5.0. Survival endpoints were assessed using the Kaplan-Meier method, and univariate and multivariate analyses were carried out to identify any potential predictive factor for an improved outcome. Results: Sixty-four lesions in 37 patients were treated using HT-SRT with a median total dose of 30 Gy in five fractions. The median follow-up was 7 months, and the 1- and 2-year LC rates were both 92.5%. The IPFS rates were and 56.75% and 51.35%. The OS rates were 54% and 40%. The UA showed better IPFS rates significantly related to male sex (p = 0.049), a BED₁₂ of ≥42 Gy (p = 0.006), and controlled extracranial disease (p = 0.03); in the MA, a favorable trend towards LC (p = 0.11) and higher BED (p = 0.11) schedules maintained a correlation with improved IPFS rates, although statistical significance was not reached. Conclusions: HT-based SRT for brain metastases showed safety and efficacy in our monoinstiutional experience. Higher RT doses showed statistical significance for improved outcomes of LC and OS.