Objective: There remains concern regarding the use of fiducial-based image-guided radiotherapy (IGRT) in patients with high-risk prostate cancer also undergoing intensity-modulated radiotherapy (IMRT) to pelvic nodes.
By a retrospective study, we aim to ascertain the impact of the use of fiducial-based IGRT on lymph node planned target volume (PTV) coverage.
Methods: 30 consecutive IMRT prostate and pelvic node plans were reviewed, and dose was recalculated with 1-mm increment movements in anterior, posterior, superior, inferior, right and left directions up to 10 mm. All patients were treated with a full bladder after drinking 450-750 ml of water and empty rectum with the use of sodium citrate enemas daily. Dose-volume histogram parameters were recorded at each position, specifically nodal PTV V95%, V99% and V100%. A local IGRT database was used to identify the likelihood of a particular bony to fiducial offset in all directions. The combined data were used to calculate the percentage risk of underdosing the lymph node PTV on any given fraction.
Results: The likelihood of an offset in the left, right and anterior directions occurring and resulting in a failure to cover the PTV was < 0.25%. The likelihood of a posterior offset occurring and resulting in inadequate coverage was slightly higher but remained < 1%.
Conclusion: This study confirms the safety of fiducial-based image-guided IMRT (IG-IMRT) with a strict bowel and bladder protocol, allowing a reduction of the clinical target volume to PTV margin of the prostate volume and consequent reduction in rectal toxicity.
Advances in knowledge: This study strengthens the evidence supporting the safe implementation of fiducial-based IG-IMRT treating the prostate and pelvic nodes in high-risk prostate cancer.
Written by:
Eminowicz G, Dean C, Shoffren O, Macdougall N, Wells P, Muirhead R. Are you the author?
Department of Radiotherapy, St Bartholomew's Hospital, London, UK.
Reference: Br J Radiol. 2014 Apr 9:20130696.
doi: 10.1259/bjr.20130696
PubMed Abstract
PMID: 24646126
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