Side Effects and Complications from Brain Irradiation
Read the review article on side
effects/complications of brain radiation here , here, here,
here and here; and radiosurgery here. There
are different types of brain injury (here)
and standard doses (here). There
are standards as to the proper dose of brain radiation from the NCCN go
here. Safe doses are described
for the brain,
optic nerve and
There is evidence that even low doses of brain radiation can effect memory (see outcome data from RTOG 0214 trial here and here) and so there is interest in a new technique to try to spare the area of brain stem cells (go here , here, here, here).
RTOG has a trial combining memantine (Namenda) with brain radiation to try to lower the risk of creating memory problems (see RTOG 0614)
see MRI brain pictures after treatment here
(Also note that chemotherapy may affect the brain, go here).
(See the side effects listed below from the RTOG.) Radiation
kills cancer cells by damaging the division of rapidly dividing cells. Since adult brain
cells no longer divide (with some exceptions) it is in fact relatively
safe to expose the brain to radiation. The 'safe' dose to the brain (6000cGy) in
much higher than for other organs of the body (go here.) Picture of radiation
necrosis of the brain here.
|In general, the dose commonly used to treat
brain metastases (300cGy X10) is thought to have very little long term risks.
In patients with primary brain tumors where the doses are higher there is some risk
of brain injury when the doses approach or exceed 6000cGy.
The picture on the left is from a patient who had high dose whole brain irradiation combined with chemotherapy.
There are specific parts of the brain that are more sensitive (e.g. the optic chiasm in patients with pituitary tumors,) and there are higher risks in patients who are also treated with chemotherapy (e.g. brain lymphoma.The short term side effects of brain radiation are usually mild: some fatigue, skin irritation and later hair loss. Some patients have hearing problems if the radiation causes swelling in the ear canal or fluid behind the ear drums. Some patients develop increased brain pressure or edema and need to be on increased doses of Decadron. Hair loss (alopecia) usually takes 2 or 3 weeks to develop and the hair usually grows back in a few months if the dose is not too high (see study below.)
after cranial irradiation: Doseresponse relationship
Lawenda BD, IJROBP 2004; 60: 879-887
One of the troubling complications resulting from cranial irradiation is permanent alopecia. The psychological effects of being diagnosed with cancer and the subsequent treatments are tremendous burdens on our patients. Hair loss is one of the most stressful side effects for patients undergoing oncologic treatment with either chemotherapy or cranial irradiation.
Temporary alopecia is a dose-dependent treatment effect that occurs in humans approximately 23 weeks after radiation exposure and usually resolves within 23 months after completion of radiotherapy (RT).. Doses as low as 2 Gy in a single fraction have been shown to cause temporary alopecia.. The historical data from the atomic bomb survivors in Hiroshima indicated that epilation was noted with estimated doses of only 0.75 Gy. The doses reported to cause permanent hair loss vary widely. A recently published analysis documented that a dose of 36 Gy (2 Gy/fraction, 5 d/wk) was reported to cause permanent alopecia in a range of 080% of patients (median risk, 5%) and that a dose of 45 Gy resulted in a risk of 5100% (median, 15%) of permanent alopecia.. International Commission on Radiological Protection Publication 85 has stated that permanent epilation occurs at 7 Gy (single fraction).. In this paper, we present a doseresponse relationship analysis for alopecia persisting at least 12 months after completion of a course of fractionated cranial irradiation.
The D50, the follicle dose at which 50% of the patients developed permanent alopecia, was estimated to be 43 Gy. No statistically significant difference was found in the D50 between patients who received radiosensitizing chemotherapy agents (i.e., cisplatin, temozolomide, and carboplatin) vs. those who received agents that were not radiosensitizing . Radiation doseresponse relationship for permanent alopecia; 95% confidence interval of dose D50 see graph.
Effects (Consent Form) from the RTOG
A PHASE II STUDY OF RADIATION THERAPY PLUS LOW DOSE TEMOZOLOMIDE FOLLOWED BY TEMOZOLOMIDE PLUS IRINOTECAN FOR GLIOBLASTOMA MULTIFORME
Risks Associated with Radiation Therapy
Common (more than 10 out of 100 patients
Uncommon (more than 1 but less than 10 patients out of 100)
Hearing loss, Dryness of the ear canal and redness of the external ear if
in radiated area
Eye injury resulting in blindness
Typical Side Effects (Consent Form) from the RTOG (RADIATION THERAPY ONCOLOGY GROUP.RTOG 0320)
Risks Associated with Whole Brain Radiation Therapy:
(Both temozolomide and gefitinib could make the radiation side effects worse.)
Scalp redness or soreness
Risks of Radiosurgery: