Radiation Therapy

Authors: Flaherty, Alice W.; Rost, Natalia S.

Title: Massachusetts General Hospital Handbook of Neurology, The, 2nd Edition

Copyright 2007 Lippincott Williams & Wilkins

> Table of Contents > Adult Neurology > Radiation Therapy

Radiation Therapy

A. Gray

= 100 rads (1 centigray = 1 rad)

B. Indications

Tumor; sometimes inoperable AVMs.

C. Doses

Risk of radiation necrosis varies with total dose.

• 1. Primary tumors: 60 Gy to involved field over 6-8 wk (5 /wk).

• 2. Metastases: 30 Gy to whole brain over 2 wk.

D. SEs

• 1. Acute: N/V, worsened deficits. Seizures rare; usually from edema. Increase steroids.

• 2. Subacute (weeks to months): Lethargy from brain XRT, Lhermitte's sign from spine radiation therapy.

• 3. Late (months to years):

  • a. Sx: Dementia, focal deficits, endocrine changes.

  • b. Causes: Radiation necrosis, leukoencephalopathy, pituitary insufficiency, new tumors (gliomas, GBM, meningiomas, nerve sheath tumors), radiation myelopathy (usually from cervical > thoracic radiation therapy).

  • c. Tests: PET, SPECT, or MRS to tell recurrent tumor from radiation necrosis. May need biopsy.

  • d. Rx: Both recurrence and necrosis respond to surgery; only recurrence responds to more XRT and chemotherapy.

E. Stereotactic radiosurgery

Uses convergent beams to deliver a high radiation dose to a small volume, sparing surrounding brain.

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Table 30. Strategies for specific compliance problems.

Compliance Problem	Treatment Strategies
Poor reporters of symptoms
Stoics	Present illness as a challenge, not a weakness
Dementia, psychosis, apathetic depression	Ask caretaker; follow PE/labs
Language barrier (all pts have this, unless they are MDs)	Use a translator, define your jargon, explain sx they should look for
Overreporters of symptoms
Anxiety, PTSD, or recent severe illness	Treat anxiety with meds or CBT, schedule routine short follow-ups
Lonely or seek sympathy	Do not tie your attention to the number of their complaints
Skilled observers (e.g., chronically ill, MD, or nurse pts)	Stress need for big picture; tell them which sx they can ignore
Med-fearing patients
Fear side effects; nocebo effect from previous rx failures	Slow drug loads; novel rx modality This one may be better
Fear dependence on meds or MD	Stress pt.'s ability to stop rx; query subst. abuse hx
Med-seeking patients
Borderline or histrionic personalities, substance abuse	Meds with low abuse potential (e.g., long acting)
Erratic or self-treating patients
MDs, PhDs, schizotypal personality, alternative	Guide rather than try to veto self-experimentation.
Dementia, psychosis	Simple regimens, have others dispense, consider depot meds
Pts. from other cultures	Ask the pt., assimilated family, or translator about pt.'s goals and fears
Over-docile patients
Dependent, passive, or fearful of authority	Encourage their (or family members') report of sx
Manipulative, ingratiating, or borderline pts.	Prepare for sudden changes in their behavior; do not overpraise

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• 1. Indications: Best for lesions 3 cm or less such as AVMs, vestibular schwannomas, pituitary adenomas, craniopharyngiomas, pineal tumors, metastases, small primary tumors. Cavernous malformations are controversial.

• 2. Methods: Gamma knife (gamma rays), LINAC (requires a linear accelerator to produce x-rays), or proton beam (requires a cyclotron to produce a beam of charged particles).

• 3. Post-op care: ACDs, analgesics, antiemetics. Complications are similar to regular XRT but with more frequent radiation necrosis.