Exclusive Hypofractionated Stereotactic Radiotherapy in Non-resectable Single Brain Metastasis

• feasibility [ Time Frame: 1 year ] [ Designated as safety issue: Yes ]
  Through this study we prospectively evaluate the alternative of performing exclusive hypofractionated stereotactic radiotherapy for patients with single brain metastasis that is not eligible for surgery or radiosurgery, with a good prognosis for survival and lower risk of metachronous brain metastases, the primary objective being to verify whether the treatment is feasible in clinical practice.
  
  

• survival [ Time Frame: 1 year ] [ Designated as safety issue: Yes ]
  As a secondary objective, we will evaluate local control, tumor reduction, quality of life, overall survival, whole-brain irradiation free survival and acute and late toxicities related to treatment.
  
  

Radiation: hypofractionated stereotactic radiotherapy
hypofractionated stereotactic radiotherapy with 4 fractions of 7 Gy at the periphery of the brain metastasis with 3 mm margin.
Other Name: hypofractionated stereotactic radiotherapy

For the planning, patients will undergo magnetic resonance imaging (MRI) 1.5 to 3 Tesla, with contrast and volumetric reconstruction of 1 mm and can be used MRI from the diagnosis of metastasis, if it is compatible with the planning system. Then, there will be individualized mask Mask Set for One Patient 41100 (BrainLAB AG, Heimstetten, Germany) for each patient. Patients will undergo computed tomography (CT) without contrast with 1-mm slices with tracking and stereotactic fixation. The images of MRI and CT are fused in the planning system IPLAN version 4.1 (BrainLAB AG, Heimstetten, Germany), where the plan will be implemented. The clinical target volume (CTV) is the macroscopic disease (GTV) displayed on the sign of T1 contrast. The planning target volume (PTV) is the CTV with 3-mm margin in all directions. Can be used multiple dynamic arcs, static conformal multiple fields, multiple static fields modulated and multiple static arcs. The dose-fractionation scheme will be 4 fractions of 7 Gy at the periphery of the PTV, a once daily on 4 consecutive working days. The dose to the PTV encompassing areas of the brainstem or optic tract will be reduced by 20%. The plans will be standardized at the isocenter. The isodose prescription will be the largest isodose that meets the following criteria: isodose covering at least 95% of the PTV with the prescription dose (V100 ≥ 95%) and 95% of prescription dose covering at least 99% of the PTV (V95 ≥ 99%) (36). The maximum dose should be less than 35 Gy. The dose constraint reported by Ernst-Stecken et al will be respected at the expense of prescription isodose, where the normal brain volume (total brain volume less volume PTV) of 20 cc will not receive a dose of 4 Gy per fraction or larger, there is no maximum size limit of metastasis to be included in the study. Use as an index of compliance reported by the Paddick et al and Radiation Therapy Oncology Group (RTOG). Tests will be done for collision safety tests and quality control to ensure the alignment of isocenters radiation, mechanical and coincidence of lasers (Winston-Lutz test). After all, the patients are treated with 6-MeV photons in the linear accelerator Varian Clinac 600 CD (Varian Medical Systems, Palo Alto, CA, USA) with a system of "micromultileaf" m3 (BrainLAB AG, Heimstetten, Germany).