We review the literature on the use of margins in the radiotherapy of the prostate cancer patients, focusing on different options for image guidance and technical issues. The search in the PubMed database was limited to include studies that involved external beam radiotherapy of the intact prostate. Post-prostatectomy studies, brachytherapy, and particle therapy were excluded. Each article was characterized according to the employed image guidance strategy used: positioning on external marks using room lasers, bone anatomy and soft tissue match, usage of fiducial markers, electromagnetic tracking, and adapted delivery. A lack of uniformity on margin selection among institutions was evident from the review. In general, introduction of pre- and in-treatment image guidance was associated with smaller PTV margins, but there was a lack of definitive experimental/clinical studies providing robust information on selection of exact PTV values. In addition there is a lack of comparative research regarding the cost benefit ratio of the different strategies: insertion of fiducial markers or electromagnetic transponders facilitates prostate gland localization but at a price of invasive procedure; frequent pre-treatment imaging increases patient in-room time, dose, and labour; on-line plan adaptation should improve radiation delivery accuracy but requires fast and precise computation. Finally, optimal protocols for quality assurance procedures need to be established.
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The British journal of radiology. 2016 Jul 05 [Epub ahead of print]
Slav Yartsev, Glenn Bauman
London Regional Cancer Program, London Health Sciences Centre and Departments of Oncology and Medical Biophysics, Western University, London, ON, Canada., London Regional Cancer Program, London Health Sciences Centre and Departments of Oncology and Medical Biophysics, Western University, London, ON, Canada.