The efficiency of CNS cancer therapy is dependent on the biological nature of the disease, radicality of the surgery and feasibility of safe application of the required radiation dose. The adverse effects of radiotherapy also depend on the radiation dose delivered.
For some CNS cancer types such as Grade 2-3 meningiomas, chordomas and chondrosarcomas, the efficiency of the treatment increases with increasing radiation dose. Dose elevation for CNS tumors is often impossible because of the presence of high-risk structures nearby or is difficult to attain by photon therapy, because of the inacceptable risk of damage of vital high-risk structures. For skull base tumors, surgical therapy is frequently incomplete. Proton therapy allows the dose to be increased up to 74-78 Gy, thus contributing to a better local control of the tumour in indicated cases. Over a five-year period, proton therapy provides 91% success rate for chondrosarcoma, 65% success rate for chordoma and 62-88% success rate for other cases.
Acute radiotherapy complications (complications arising during or shortly after the exposure) include nausea, focal alopecia and otitis. The most serious delayed complications include impaired cognitive functions, vision disorders (some of which can be remedied by surgery, i.e. lens replacement, while others are permanent), impaired pituitary function, brain tissue necrosis, increased fractions of deaths due to diseases of cerebrovascular etiology.
The number of secondary brain tumors also grows with increasing integral radiation dose. (Minniti G, Traish D, Ashley S, et al. Risk of second brain tumor after conservative surgery and radiotherapy for pituitary adenoma: update after an additional 10 years. J Clin Endocrinol Metab 2005;90:800-804).
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