1341- 52; discussion 1353- 6. I-ATTAC Version: 20220204 63 18 APPENDICES 18.1 Standard Radiation Therapy Radiotherapy typically begin s within ≤ 5 weeks of surgery. One treatment of 1.8- 2.0 Gy/fra ction will be given daily 5 days per week for a total of 59.4- 60.0 Gy over <7 weeks. 3D conformal and intensity -modulated RT is permitted. All portals should be treated during each treatment session. Doses are specified as the target dose that shall be to the center of the target volume. The gross target volume (GTV) for both the initial volume (GTV1) and the conedown volume (GTV2) should be based on the postoperative CT/MRI (and preferably the MRI; the preoperative scans may be used if postoperative scan s are not available). This initial target volume (GTV1) should include the contrast -enhancing lesion (and should include the surgical resection cavity) and surrounding edema (if it exists) demonstrated on CT/MRI plus a 2.0- cm margin (this 2.0- cm margin -extended volume will be considered the initial planning target volume, or PTV1). The initial target volume should be treated to 46 Gy at 2Gy/fraction or 45 -50.4 Gy at 1.8Gy/fraction. If no surrounding edema is present, the initial planning target volume (PTV1) should include the contrast -enhancing lesion (and should include the surgical resection cavity) plus a 2.5- cm margin. Please note that clinical judgment may be used to modify PTV1 to exclude sensitive structures such as the optic chiasm, non- cranial cont ents, or anatomic regions in the brain where natural barriers would likely preclude microscopic tumor extension, such as the cerebellum, the contralateral hemisphere, directly across from the tentorium cerebri, the ventricles, etc. After 46 Gy, the tumor volume (GTV2) for the conedown treatment should include the contrast -enhancing lesion (without edema) on the pre -surgery CT/MRI scan plus a 1.5- 2-cm margin (PTV2). Treat to 14 Gy at 2Gy/fraction or 14.4- 9.0 Gy at 1.8Gy/fraction to a total of 60.0 or 59.4Gy, respectively. Dose is prescribed to the isodose line such that at least 95% of the target volume receives he prescribed dose. The optic apparatus should be limited to a maximum of 54Gy and no more than 5% of the volume of the brainstem should receive >54Gy. Radiation should be delayed or interrupted if the platelet count is < 20,000. Radiation should not begin or resume until the platelet count is ≥ 20,000. Hematologic toxicities should be rated on a scale of 0 -5 as defined in the NCI Common Terminology Criteria for Adverse Events (CTCAE) version5.0. If radiotherapy has to be temporarily interrupted f or technical or medical reasons unrelated to the temozolomide administration, then treatment with daily temozolomide should continue. If radiotherapy has to be permanently interrupted then treatment with daily temozolomide should stop. The following shoul d be recorded at entry into this study: daily treatment record, all isodose distributions (in color), dose volume histograms including the cumulative dose to the target volumes, optic chiasm, optic nerves and brain stem, and the radiotherapy summary. 18.2 Temozolomide Therapy Please refer to the current package insert for Temodar®.