Implementing Surface Guided Stereotactic Radiotherapy (SG-SRT) at One Institution in Colombia: Experience of the First Year of a New Paradigm of Radiotherapy in a Developing Country

Abstract

Stereotactic Hypofractionated Radiotherapy (SRT, including SRS, SBRT and SART) is increasingly becoming the treatment of choice for several clinical situations, both in curative and palliative cases. Moreover, the shorter duration of treatments is an advantage for both the patients and the health care system of low- and middle-income countries, such as ours, because hypofractionation implies the possibility of treating a greater number of patients with the installed capabilities. In Colombia there are 67 megavoltage machines, few of which are dedicated radiosurgery and stereotactic machines. These machines are located in big cities and are often out of reached for public healthcare patients, who end up receiving normal fractionation conformal treatments that have long been proved inferior to SRT. With this scarcity of technology to implement SRT, and considering that most of the technology in our country consists of gantry based LINACS with MLC systems, it is worth considering LINAC based SRT. The aim of this study was to evaluate the efficacy and safety of a Surface Guided System couple with Cone Beam CT (CBCT) or kV imaging to implement SRT in a LINAC with 0.5 mm MLC. To our knowledge this is the first experienced with SG-SRT reported in South America. Between Nov 1 2018 and Oct 31 2019, 86 patients were treated with SG-SRT, 44 women and 42 men, with ages 20-91 years (MED 63 y). ROI for surface guidance was defined for each patient after initial positioning with CBCT or kV imaging, and used for intrafraction monitoring in every fraction. CBCT or kV imaging was taken in more than 80% of treatment fractions for 78 patients, and at least in 50% of fractions for the other 8. The median of the total dose was 30Gy (20Gy-50Gy) and the median of the dose per fraction was 5Gy (5Gy-20Gy). The median of the PTV was 33.25 cc (0.9-291.53). 1 patient received SRS for AVM (20Gy), 8 received SBRT for lung (dose per fraction range 7Gy-10Gy), 3 received SBRT for other causes (35Gy/5 Fractions), and the rest received hypofractionated radiotherapy (5 or 6 GY per fraction) for different causes, mainly brain (19), nodal (11) and lung (7) metastases. All 86 patients finished the treatment without any delay attributable to complications from it. With a median follow up of 3 months (range 0-15) we observed no ≥3 grade acute or late toxicity in any of the treated patients. 85% of patients with imaging studies after treatment (46/54) achieved local control and 98% of patients (62/63) with clinical follow up achieved some level of symptomatic improvement. 22 patients (26%) did not come for clinical or imaging control after treatment. The average of new cases per month in our practiced increased by 13.5%. Surface guidance coupled with CBCT or kV imaging enabled us to perform SRS, SBRT and SRT. Our early experienced demonstrates that SG-SRT is an effective and safe alternative to bring cutting edge, much needed, stereotactic radiotherapy treatments to patients in the developing world.