LDR brachytherapy : can low dose rate hypersensitivity from the inverse dose rate effect cause excessive cell killing to peripherial connective tissues and organs?

Examined here are the possible effects of the "inverse" dose rate effect (IDRE) on low dose rate (LDR) brachytherapy. The hyper-radiosensitivity and induced radioresistance (HRS/IRR) effect benefits cell killing in radiotherapy, and IDRE and HRS/IRR seem to be generated from the same radio...

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Bibliographic Details
Published in:British journal of radiology 2009-02, Vol.82 (974), p.131-139
Main Authors: LEONARD, B. E, LUCAS, A. C
Format: Article
Language:English
Subjects:
Biological and medical sciences
Brachytherapy - adverse effects
Brachytherapy - methods
Cell Death - radiation effects
Connective Tissue - radiation effects
Dose-Response Relationship, Radiation
Female
Humans
Intestines - radiation effects
Investigative techniques, diagnostic techniques (general aspects)
Medical sciences
Models, Biological
Radiation Injuries - etiology
Radiation Tolerance
Radiobiology - methods
Radiotherapy Dosage
Urinary Tract - radiation effects
Uterine Cervical Neoplasms - radiotherapy
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Summary:Examined here are the possible effects of the "inverse" dose rate effect (IDRE) on low dose rate (LDR) brachytherapy. The hyper-radiosensitivity and induced radioresistance (HRS/IRR) effect benefits cell killing in radiotherapy, and IDRE and HRS/IRR seem to be generated from the same radioprotective mechanisms. We have computed the IDRE excess cell killing experienced in LDR brachytherapy using permanent seed implants. We conclude, firstly, that IDRE is a dose rate-dependent manifestation of HRS/IRR. Secondly, the presence of HRS/IRR or IDRE in a cell species or tissue must be determined by direct dose-response measurements. Thirdly, a reasonable estimate is that 50-80% of human adjoining connective and organ tissues experience IDRE from permanent implanted LDR brachytherapy. If IDRE occurs for tissues at point A for cervical cancer, the excess cell killing will be about a factor of 3.5-4.0 if the initial dose rate is 50-70 cGy h(-1). It is greater for adjacent tissues at lower dose rates and higher for lower initial dose rates at point A. Finally, higher post-treatment complications are observed in LDR brachytherapy, often for unknown reasons. Some of these are probably a result of IDRE excess cell killing. Measurements of IDRE need be performed for connective and adjacent organ tissues, i.e. bladder, rectum, urinary tract and small bowels. The measured dose rate-dependent dose responses should extended to
ISSN:0007-1285
1748-880X
DOI:10.1259/bjr/66381835