Table of Contents
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Bone Marrow
- Circulating lymphocytes are directly killed by low dose radiation (TBI)
Breast
- Preadolescent breast development is inhibited in 5% of the population at 10 Gy and 50% at 15 Gy.
CNS
- Oliogodendrocytes are responsible for myelination
- For pediatric patients with localized ependymoma, a limited volume of the upper cervical spinal cord may receive 54 Gy over the course of 6 weeks with minimal risk of spinal cord injury. Additional dose to the spinal cord beyond 54 Gy does not contribute additional risk, phttp://www.wikidot.com/doc:wiki-syntaxrovided the daily fraction size is limited to 1.25 Gy. (T. E. Merchant. A Prospective Study of Spinal Cord Dosimetry and Neurologic Outcome for Infratentorial Ependymoma. IJROBP 1 November 2006 (Vol. 66, Issue 3, Page S111))
Cauda equina
- No patients devleoped neural injury at ≤ 70.2 Gy RBE. Suspect nerve injury to occur between 70.2 to 77.4 Gy[13]
Brachial Plexus
- .4% complication with ≤ 50 Gy without chemotherapy and 3.4% with chemotherapy
- 60 Gy can be delivered with complications in <5% of patients. ( Choa KS, Perez C, Brady L. Radiation Oncology: Management Decisions. Philadelphia, PA: Lippincott-Raven Publishers, 1999. )
Treatment
- trandermal electrical nerve stimulation
- dosal column stimulators
- neurolysis
- neurolysis with omentoplasty
- physical therapy
- tricyclics
- antiarrhythmics
- anticonvulsives
- NSAID and Steroids
SBRT
- The 2-year risk of brachial plexopathy was 46% after the brachial plexus received a biologically effective dose maximum (BED) of >100 Gy
- 8% for BED <100 Gy [6].
- Anther study reported brachial plexopathy in 1 of 60 patients due to significant volume of brachial plexus receiving 40 Gy in 4 fractions. [7]
EAR (COCHLEAR)
- a significant hearing loss was noted after a cochlear dose of ≥ 60 Gy in 60% of the patients and no patient after a dose of < 60 Gy when treating the parotid in adults. (Chen et al Ann Otol Rhinol Laryngol 1999; 108: 1159-1164).
- a dose of ≤ 30 Gy should be attempted.
Eye
Lens of eye(Cataract)
- Min. dose = 2Gy
- RBE of neutron or heavy iron is 20 but as high as 50
- Result of accumulation of dead cells
- 2-6.5 Gy Stationary cataract
- 6.5-11.5 Gy Progressive Cataract
Lung
General
- is an intermediate- to late-responding tissue with alpha/beta of 3. The lung is among the most sensitive of late-responding tissues.
Radiation Pneumonitis
- surfactant proteins, IL-6, and IL-1α] have been identified as early circulating cytokine markers for RP. Anscher et al. (IJROBP 1998)[28] have extensively evaluated in clinical studies the role of plasma transforming growth factor-β1 (TGF-β1) in the development of RP.
- (Katrien De Jaeger M.D., M.Sc. Significance of plasma transforming growth factor-β levels in radiotherapy for non–small-cell lung cancer IJROBP 1 April 2004, Pages 1378-1387)
== DVH for Lung and Surrounding Tissues for Lung Irradiation ==
Radiation Bronchitis
This disease entity was originally described by Speiseret al.[12] The concept of the hyperdose sleeve may reasonably explain the high dose volume produced by intraluminal brachytherapy sources.[11] As for the proximal airway, several series have reported tracheal stenosis after external beam radiation therapy using up to 70 Gy.[8],[9] Hayakawa et al. reported the deleterious effect of 80 Gy in 40 fractions to the proximal bronchi.[10]
GI
Liver
- no upper limit if < 25% of the normal liver is treated
- 5% risk for uniform irradiation of
1/3 | 90 Gy |
2/3 | 47 Gy |
whole liver | 31 Gy |
(Dawson et al. Sem Rad Onc 01).
OVARY
Radiation Effect On Fertility: Ovary[5]
• Under 2Gy radiation can destroy 50% of
the immature oocytes
• 20-30 Gy total abdominal therapy
– 97% post-pubertal women experience premature ovarian failure
– 72% pre-pubertal girls lose ovarian function
• Degree of ovarian dysfunction is related to
– Dose
– Fractionation schedule
– Age and time of therapy
– Gonadal shielding
Skin
- Low dose hypersensitivity can occur at 0.5 Gy per fraction*
- At 2 Gy maximum resistance to radiation occurs and skin erythema is rarely seen from 2-7 Gy
Small Bowel Tolerance
Testes
- Transit time from stem cell to spermatozoa is 74 days.
- 0.1 Gy leads to tremporary reduction in # of spermatozoa
- 0.15 Gy leads to temp. sterility
- 2 Gy leads to Azoospermia x 2 years
- 6-8 Gy permanent Azoospermia.
- 1 Gy TD 5/5 for Sterility
- 20 Gy TD 5/5 for Leydig cells (testosterone)
- B-spermatogonia are killed
- Fractionation decreases the tolerance for sterility due to reassortment
TESTIS
Radiation Effect On Fertility: Testis[3],[4]
• Dose dependent effect on sperm parameters
– Greater than 4-6 Gy: permanent azoospermia
– Greater than 1.2 Gy: azoospermia
– Lower doses show varying degrees and durations of sperm impairment
– Direct testicular irradiation has an 8.2-fold increase risk of azoospermia
Vaginal Surface Dose tolerance in thirds[1]
- Proximal 150 Gy
- "The traditional 150 Gy LDR tolerance dose (single source plus external irradiation) can be relaxed to 175 Gy or equivalently a full mucosal dose of 238 Gy (all sources plus external irradiation) for a nominal 5% Grade 3 complication rate."[2]
- Middle 90 Gy
- Distal 90 cGy
- Whole vaginal < 80 Gy
Treatment of Fibrosis
Pentoxifylline
- and inhibitors of TGF-beta can reduce fibrosis even afer its clinical development.
TGF-beta
- Potent growth inhibitor and inducer of apoptosis, suppresses anti-tumor immune responses. binds to type I and type II receptors leading to signaling of SMAD family of intracellular mediators.