Concise review of stereotactic irradiation for pediatric glial neoplasms:Current concepts and future directions

Brain tumors,which are among the most common solid tumors in childhood,remain a leading cause of cancer-related mortality in pediatric population.Gliomas,which may be broadly categorized as low grade glioma and high grade glioma,account for the majority of brain tumors in children.Expectant management,surgery,radiation therapy(RT),chemotherapy,targeted therapy or combinations of these modalities may be used for management of pediatric gliomas.Several patient,tumor and treatment-related characteristics including age,lesion size,grade,location,phenotypic and genotypic features,symptomatology,predicted outcomes and toxicity profile of available therapeutic options should be considered in decision making for optimal treatment.Management of pediatric gliomas poses a formidable challenge to the physicians due to concerns about treatment induced toxicity.Adverse effects of therapy may include neurological deficits,hemiparesis,dysphagia,ataxia,spasticity,endocrine sequelae,neurocognitive and communication impairment,deterioration in quality of life,adverse socioeconomic consequences,and secondary cancers.Nevertheless,improved understanding of molecular pathology and technological advancements may pave the way for progress in management of pediatric glial neoplasms.Multidisciplinary management with close collaboration of disciplines including pediatric oncology,surgery,and radiation oncology is warranted to achieve optimal therapeutic outcomes.In the context of RT,stereotactic irradiation is a viable treatment modality for several central nervous system disorders and brain tumors.Considering the importance of minimizing adverse effects of irradiation,radiosurgery has attracted great attention for clinical applications in both adults and children.Radiosurgical applications offer great potential for improving the toxicity profile of radiation delivery by focused and precise targeting of well-defined tumors under stereotactic immobilization and image guidance.Herein,we provide a concise review of stereotactic irradiation for pediatric glial neoplasms in light of the literature.

STEREOTACTIC IRRADIATION OF LUNG CANCER

Objective: To investigate the best stereotactic irradiation (STI) technique in treatment of small lung tumors, using dose-volume statistics. Methods: Dose-volume histogram (DVH) of the study phantom consisting of CT using the software of FOCUS-3D planning system. The beam was a 6MV X-ray from a Varian 2300C. The analysis data of Dose-volume statistics was from the technique used for: (1) 2–12 arcs; (2) 20°–45° separation angle of arcs; (3) 80°–160° of gantry rotation. Then we studied the difference of DVH with various irradiation techniques and the influence of target positions and field size by calculated to the distribution of dose from 20%–90% of the six targets in the lung with 3×3 cm2, 4×4 cm2 and 5×5 cm2 field size. Results: The volume irradiated pulmonary tissue was the smallest using a six non-coplanar 120° arcs with 30° separation between arcs in the hypothetical set up, the non-coplanar SRI was superiority than conventional one’s. The six targets were chosen in the right lung, the volume was the largest in geometric center and was decreased in hilus, bottom, anterior chest wall, lateral wall and apex of the lung in such an order. The DVH had significant change with an increasing field size. Conclusion: the irradiation damage of normal pulmonary tissue was the lowest using the six non-coplanar 120° arcs with a 30° separation between arcs by <5×5 cm2 field and the position of target was not a restricting factor.

Concise review of radiosurgery for contemporary management of pilocytic astrocytomas in children and adults

Pilocytic astrocytoma(PA)may be seen in both adults and children as a distinct histologic and biologic subset of low-grade glioma.Surgery is the principal treatment for the management of PAs;however,selected patients may benefit from irradiation particularly in the setting of inoperability,incomplete resection,or recurrent disease.While conventionally fractionated radiation therapy has been traditionally utilized for radiotherapeutic management,stereotactic irradiation strategies have been introduced more recently to improve the toxicity profile of radiation delivery without compromising tumor control.PAs may be suitable for radiosurgical management due to their typical appearance as well circumscribed lesions.Focused and precise targeting of these well-defined lesions under stereotactic immobilization and image guidance may offer great potential for achieving an improved therapeutic ratio by virtue of radiosurgical techniques.Given the high conformality along with steep dose gradients around the target volume allowing for reduced normal tissue exposure,radiosurgery may be considered a viable modality of radiotherapeutic management.Another advantage of radiosurgery may be the completion of therapy in a usually shorter overall treatment time,which may be particularly well suited for children with requirement of anesthesia during irradiation.Several studies have addressed the utility of radiosurgery particularly as an adjuvant or salvage treatment modality for PA.Nevertheless,despite the growing body of evidence supporting the use of radiosurgery,there is need for a high level of evidence to dictate treatment decisions and establish its optimal role in the management of PA.Herein,we provide a concise review of radiosurgery for PA in light of the literature.