Bridging the Gap: First Clinical Experience With Linear Accelerator (LINAC) Radiosurgery Using Automated HyperARC for Brain Metastasis in a Low-Resource Setting in Pakistan

Introduction Brain metastasis is becoming increasingly common in cancer patients. Over the past decade, stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (fSRT) have become the cornerstone of treatment for limited brain metastases. Sophisticated linear accelerator (LINAC)-based HyperArc volumetric modulated arc therapy (HA-VMAT) systems offer the unique advantage of high-precision radiotherapy. The purpose of this study is to present our first clinical experience with the HA-VMAT planning approach for brain metastases treated at our hospital. Methods This retrospective study included 72 patients with 1-5 brain metastases treated at our institution with SRS/SRT using HA-VMAT. A dosimetric evaluation of clinical characteristics and outcomes was carried out. Results From April 2020 until June 2021, a total of 86 brain metastases in 72 patients were treated. The median age was 45 (range 18-75). The most common histology was breast cancer (n = 48 (66.7%)). Sixty-two (86.1%) patients had a single brain metastasis. Thirty-two (44%) patients were treated with single-fraction SRS, while 40 (65%) received fSRT. The radiobiological equivalent dose in 2 Gy fractions (EQD2) ranged from 50.4 to 81.6 Gy for SRS and from 37.25 to 60.0 Gy for fSRT. The median GTV and PTV volumes for a single fraction were 1.98 cc (range 0.13-13.3) and 4.49 cc (range 0.64-21.20), respectively. The mean PTV was 10.96 cc (range 2.25-34) and 19.04 cc (4.40-75.88). Complete response was observed in 12.5% of the patients. The median follow-up was 17 months (range 1-38 months). The progression-free survival at 1 year was 54.6%. Only one patient developed radiation necrosis. Conclusion Brain metastases can be safely and effectively treated with SRS/fSRT using HA-VMAT, which decreases the likelihood of local complications and improves local control.