title: Dosimetric comparison between high-precision external beam radiotherapy and endovascular brachytherapy for coronary artery in-stent restenosis.
abstract: OBJECTIVE
  Several drawbacks of endovascular brachytherapy for the treatment of coronary artery in-stent restenosis may be addressed by high-precision external beam radiotherapy (EBRT). The dosimetric characteristics of both treatment techniques were compared.
  
  
  METHODS
  The traversed volume of 10 coronary artery stents during the cardiac cycle was determined by electrocardiographically gated multislice spiral CT in 10 patients. By use of this traversed volume, high-precision EBRT treatment plans were generated for stents in the left circumflex (LCx), left anterior descending (LAD), and right coronary artery (RCA). The maximum dose to the nontargeted major coronary arteries was determined and compared to similar data calculated for endovascular brachytherapy.
  
  
  RESULTS
  High-precision EBRT targeted at LCx stents contributed a mean maximum dose (D(max)) of 83.5% (range: 71.6-95.3%) and 16.3% to the LAD and RCA, respectively. Targeted LAD stents contributed a mean D(max) of 39.3% (range: 14.5-94.8%) and 5.2% (range: 0-13.4%) to the LCx and RCA, respectively. Targeted RCA stents contributed a mean D(max) of 6.2% (range: 0-12.4%) and 5.8% (range: 0-11.5%) to the LCx and LAD, respectively. Endovascular brachytherapy targeted at LCx stents contributed a mean D(max) of 1.7% (range: 0.7-2.7%) and 1.0% (range: 0.6-1.4%) to the LAD and RCA, respectively. Targeted LAD stents contributed a mean D(max) of 5.2% (range: 0.5-11.4%) and 0.7% (range: 0.4-1.1%) to the LCx and RCA, respectively; targeted RCA stents contributed a mean D(max) of 0.3% (range: 0.2-0.5%) and 0.2% (range: 0.1-0.3%) to the LCx and LAD, respectively.
  
  
  CONCLUSIONS
  Although the doses distributed throughout the heart were higher for high-precision EBRT compared to endovascular brachytherapy, they are expected to be clinically irrelevant when nontargeted major coronary arteries are not closely situated to the targeted vessel segment. These encouraging results warrant further investigation of high-precision EBRT as a potential alternative to endovascular brachytherapy for the treatment of coronary artery in-stent restenosis.
authors.affiliation: Department of Radiation Oncology, Erasmus Medical Center, Daniel den Hoed Cancer Center, Groene Hilledijk 301, 3075 EA Rotterdam, The Netherlands.
authors.forename: Edward M
authors.initials: EM
authors.lastname: Leter
authors.forename: Peter J C M
authors.initials: PJ
authors.lastname: Nowak
authors.forename: Koen
authors.initials: K
authors.lastname: Nieman
authors.forename: Johannes P
authors.initials: JP
authors.lastname: Marijnissen
authors.forename: Stéphane G
authors.initials: SG
authors.lastname: Carlier
authors.forename: Connie
authors.initials: C
authors.lastname: de Pan
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Serruys
authors.forename: Peter C
authors.initials: PC
authors.lastname: Levendag
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D023903:Coronary Restenosis / Q000532:radiotherapy*; D003331:Coronary Vessels / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011874:Radiometry; D011879:Radiotherapy Dosage; D015607:Stents