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What is Cranial irradiation is useful in treatment of? and explain in detail?
Ans. D. All of the above. (Ref. Walter and Miller's Textbook of Radiotherapy 7th/Ch. 33)Craniospinal irradiation is used for patients who have, or are at risk for, disseminated disease throughout the CNS that is not sufficiently responsive to chemotherapy (typically methotrexate). This includes:# Embryonal CNS malignancies (medulloblastoma, PNET, atypical teratoid/rhabdoid tumour)# Intracranial germ cell tumour with evidence of distant CNS metastases.# Epenedymoma with evidence of distant CNS metastases or CSF involvement- Craniospinal radiation is central to the management of medulloblastoma. Depending upon the age and the use of chemotherapy, cranio-spinal irradiation (CSI) of 25 to 35 Gy and boost radiation to the posterior fossa to a total dose of 50-55Gy over 6-7 weeks is the standard of care.- Post operative radiotherapy (localised fields to a dose of 54 Gy/30) is required in selected cases with residual cerebellar astrocytoma particularly in the brain stem. Chemotherapy is generally not indicated in these tumours.- In germinomas, Radiotherapy directed toward the craniospinal axis or tumor site alone at decreased dose levels is effective.Tumours with high propensity for neuraxis dissemination include :# medulloblastoma, intracranial germ cell tumour, primary CNS lymphoma and undifferentiated round cell tumours such as ependymoblastoma and PNET.