Radiosurgery and hypofractionated reirradiation in progression of hemispheric glioblastomas

Abstract

Introduction. Glioblastomas (WHO grade IV) are the most common primary malignant tumors of the CNS with an extremely poor prognosis. Despite combined treatment, which includes maximal surgical removal followed by radiation and chemotherapy, the vast majority of cases experience progression within several months after surgery. Repeated radiation therapy is one of the most common and effective therapeutic options when progression is detected.

Aim. To study the efficacy and safety of stereotactic radiation therapy in treating glioblastoma progression in radiosurgery and hypofractionation modes.

Materials and methods. The study included 163 patients with glioblastoma (GB) progression after complex treatment from 2005 to 2021. All patients were treated in the radiotherapy department of the National Medical Research Center for Neurosurgery and the Moscow Gamma Knife Center. The age of patients included in the study ranged from 18 to 73.9 years. The median age was 49.5 years (95 % CI 47-52.3). In the mode of radiosurgery (for one fraction), 180 foci were treated (located "locally" within 3 cm from the prescribed isodose at primary irradiation — 122, and 58 — distant). In the hypofractionation mode, 107 foci were treated (local — 67 and distant — 40). The mean volumes of foci were 9.2 cm³ (0.01-43.2 cm³) in the radiosurgery mode and 17.84 cm³ (0.1-72 cm³) in the hypofractionation mode. The median prescribed dose in the radiosurgery mode was 20 Gy at 50 % of the isodose curve. The median cumulative focal dose in the hypofractionation mode was 30 Gy.

Results. Analysis of the treatment results in radiosurgery mode showed that for local progression, local control at 3, 6, and 12 months was 98.1 %, 76.3 %, and 38.5 %, respectively, while for distant progression it was 100 %, 80.1 %, and 67.2 %, respectively. In hypofractionation mode, the local control of foci of local progression at 3, 6, and 12 months was 90.2 %, 73.2 %, and 23.6 %, respectively, and for distant progression it was 97.6 %, 86.2 %, and 59.4 %, respectively.

Grade 3 radiation toxicity after radiosurgery was observed in 8.8 % of patients. Grade 3-4 radiation toxicity after hypofractionation in the form of edema was observed in 18.2 % of patients, and post-radiation necrosis was observed in 13.4 % of patients. In the hypofractionation mode, the mean volume of the focus in the group with post-radiation toxicity was 22.7 cm³, while in the group without post-radiation toxicity it was 15.2 cm³.

Conclusion: Stereotactic radiotherapy for glioblastoma progression in radiosurgery and hypofractionation modes is an effective and safe treatment option that leads to an increase in the duration of local tumor control. Repeating radiotherapy for distant glioblastoma progression significantly increases local control compared to local progression.