Facts to watch for when taking exams:

• Most Common brain and bone tumors are : metastases (not asking for primary just asking tumor!! Don't be fooled)

• Breast and Prostate metastasize to the spine, ribs, hips, proximal long bones (closer to midline)

• Mets are given a dose of 3000 cGy in 10 Fractions (must include in 10 fractions!!!)

• 3 T’s of Radiation Therapy : Tumor Volume , Target Volume and Treatment Volume

and now back to the CNS :

Decadron : medication that is given to brain tumor patients to reduce the swelling (the RT treatments will cause additional swelling and will cause problems if the problem is not addressed pre treatement)

• Patient must be started on the Decadron before they start their radiation treatments
• Anti-inflammatory drug
• If Decadron cannot be started in enough time (emergency cases) then the patient must have Decompression Surgery to reduce the swelling

Standard Doses for Primary Brain Tumors :

• Large Field is given 4500 cGy + Boost of 1500 cGy (Total Dose 6000 cGy)
• Surgery will be performed first if possible

Medulloblastoma : most common primary brain tumor in children

Medulloblastomas are malignant tumors formed from poorly developed cells at a very early stage of their life. They develop in the cerebellum, in a part of the brain called the posterior fossa, but may spread to other parts of the brain. Very rarely they may spread to other parts of the body. Spread to other parts of the brain or to the spinal cord is usually through the cerebrospinal fluid (CSF). CSF is the fluid around the brain and the spinal cord.

• MOST RADIOSENSITIVE OF ALL PRIMARY BRAIN NEOPLASMS
• Occurs in the posterior fossa of the cerebellum (therefore will effect balance, walking , etc…..)
• Meninges are effect along with the CSF therefore we must treat the entire brain with along with the entire length of the spinal cord to S2
• Intrathecal Chemo is often used and is injected directly into the CSF
• Since the whole brain will be treated along with the spinal cord we must decide how many fields we will need according to the height of the patient

• Patient will usually be in the prone position (so not to treat through critical organs

• Usually requires the lateral whole brain with 2 posterior spine fields (if possible the spine fields will be gaped below the active length of the spinal cord (L2) which to give enough margin for the gap will be L4

• We don’t want to match the fields along the active length of cord

• Some institutions use junction shifts on a daily or weekly basis (shift were the fields meet each day)

• Gap calculation is used to determine the junctions

• Dose to the spine will be 3000 cGy  (SSD)

• Dose to the whole brain will be 4000 cGy with a 1000 cGy boost the cerebellum  (SAD)  German Helmet is used to treat the outer edges of the brain including the base of skull

• To accommodate for the divergence of the SPINE FIELD we will collimate when treating the WHOLE BRAIN
• To accommodate for the divergence of the WHOLE BRAIN FIELD (to the SPINE FIELD) we will kick the couch when treating the WHOLE BRAIN field.  The head of the couch will be kicked away from the head of the Gantry.
• note: if any of the fields overlap and overdose will occur