RESUMO
OBJECTIVE: To evaluate the possibility of dose de-escalation, with consideration of the efficacy and safety of robotic stereotactic CyberKnife radiotherapy in patients diagnosed with intracranial meningiomas. METHODS: The study group consisted of 172 patients (42 men and 130 women) treated in III Radiotherapy and Chemotherapy Clinic of Maria Sklodowska-Curie National Research Institute of Oncology in Gliwice between January 2011 and July 2018. The qualification for dose de-escalation was based on MRI (magnetic resonance imaging) features: largest tumor diameter less than 5 cm, well-defined tumor margins, no edema, and no brain infiltration. The age of patients was 21-79 years (median 59 years) at diagnosis and 24-80 years (median 62 years) at radiotherapy. Sixty-seven patients (Group A) were irradiated after initial surgery. Histopathological findings were meningioma grade WHO 1 in 51 and WHO 2 in 16 cases. Group B (105 patients) had no prior surgery and the diagnosis was based on the typical features of meningioma on MRI. All patients qualified for the robotic stereotactic CyberKnife radiotherapy, and the total dose received was 18 Gy in three fractions to reference isodose 78-92%. RESULTS: Follow-up period was 18 to 124 months (median 67.5 months). Five- and eight-year progression free survival was 90.3% and 89.4%, respectively. Two patients died during the follow-up period. Progression of tumor after radiotherapy was registered in 16 cases. Four patients required surgery due to progressive disease, and three of them were progression free during further follow-up. Twelve patients received a second course of robotic radiotherapy, 11 of them had stable disease, and one patient showed further tumor growth but died of heart failure. Crude progression free survival after both primary and secondary treatment was 98.8%. Radiotherapy was well-tolerated: acute toxicity grade 1/2 (EORTC-RTOG scale) was seen in 10.5% of patients. We did not observe any late effects of radiotherapy. CONCLUSION: Stereotactic CyberKnife radiotherapy with total dose of 18 Gy delivered in three fractions showed comparable efficacy to treatment schedules with higher doses. This could support the idea of dose de-escalation in the treatment of intracranial meningiomas.
RESUMO
Due to somatostatin receptor expression in meningiomas, PET with somatostatin analogs appears to be useful in radiotherapy treatment planning. We report the case of a 63-year-old man diagnosed with meningioma of the left frontal lobe in 2011. He underwent total tumor excision (pathology was atypical meningioma WHO 2) and radiotherapy, but one year after the completion of treatment, he complained about diplopia and left upper eyelid ptosis. The MRI showed a new parasagittal lesion and the patient received stereotactic radiotherapy. Few weeks later, two new lesions were found - one in the sella turcica region and the other adjacent to the greater wing of the right sphenoid bone. The patient underwent transsphenoidal biopsy, but was not qualified for neurosurgery due to high risk of bleeding. In the radiotherapy treatment planning, we used a fusion of MRI and 68Ga-DOTA-(Tyr3)-octreotate PET/CT images. The patient received stereotactic radiotherapy, first to the parasellar lesion and then to the progressing tumor adjoining the sphenoid bone. In both cases, PET/CT scans helped to define the target, its volume being bigger on PET/CT than on MRI images. In patients with meningiomas, 68-Ga-DOTA-(Tyr3)-octreotate PET/CT can be considered as a useful imaging modality in radiotherapy treatment planning, which helps to visualize the tumor extension and to define the target.
