title: Improving cardiac dosimetry: Alternative beam arrangements for intensity modulated radiation therapy planning in patients with carcinoma of the distal esophagus.
abstract: OBJECTIVE
  Radiation for carcinoma of the distal esophagus is associated with cardiac perfusion deficits and pericardial effusion. We performed a dosimetric analysis of alternative beam arrangements for use in intensity modulated radiation therapy (IMRT) planning, seeking to lower radiation dose to the heart.
  
  
  METHODS
  Treatment plans using 4 separate beam arrangements were generated and optimized for 12 patients. Hemispheric and butterfly beam arrangements were compared with plans with posterior and lateral beam entries. Radiotherapy was planned to 50.4 Gy in 28 fractions, using step and shoot IMRT with 6 MV photons. Mean heart dose and volumes of heart and lung receiving up to specified doses (V5-V40) were recorded. Isodose distributions were evaluated for target coverage and normal tissue exposure.
  
  
  RESULTS
  IMRT plans utilizing posterior-lateral beam arrangements significantly reduced mean cardiac doses (32.5 ± 3.9 Gy, 33.3 ± 3.2 Gy vs 24.3 ± 3.7 Gy, and 23.4 ± 4.2 Gy, P < .05, paired Student t test with post hoc Bonferroni correction) as well as the total heart volumes receiving at least 20 and 30 Gy. IMRT allowed the maximum cord dose to be limited to less than 40 Gy. While both posterior-lateral beam arrangements lead to improved cardiac dosimetry, mean lung doses as well as V5 and V20 were slightly higher, although within accepted limits. Target coverage, homogeneity, and conformality were similar or improved with the use of alternative beam configurations.
  
  
  CONCLUSIONS
  The use of IMRT with posterior-lateral beams can significantly reduce radiation dose to cardiac structures with minimal increased dose to the lung. Future studies will assess the physiologic and clinical impact of cardiac sparing.
authors.affiliation: Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
authors.forename: David
authors.initials: D
authors.lastname: Grosshans
authors.affiliation: Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Boehling
authors.affiliation: Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
authors.forename: Matthew
authors.initials: M
authors.lastname: Palmer
authors.affiliation: Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
authors.forename: Chris
authors.initials: C
authors.lastname: Spicer
authors.affiliation: Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
authors.forename: Rolly
authors.initials: R
authors.lastname: Erice
authors.affiliation: Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
authors.forename: James D
authors.initials: JD
authors.lastname: Cox
authors.affiliation: Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas.
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
authors.affiliation: Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas. Electronic address: jychang@mdanderson.org.
authors.forename: Joe Y
authors.initials: JY
authors.lastname: Chang