Evaluation of four techniques using intensity-modulated radiation therapy for comprehensive locoregional irradiation of breast cancer.
OBJECTIVE
To establish optimal intensity-modulated radiation therapy (IMRT) techniques for treating the left breast and regional nodes, using moderate deep-inspiration breath hold.


METHODS
We developed four IMRT plans of differing complexity for each of 10 patients following lumpectomy for left breast cancer. A dose of 60 Gy was prescribed to the boost planning target volume (PTV) and 52.2 Gy to the breast and supraclavicular, infraclavicular, and internal mammary nodes. Two plans used inverse-planned beamlet techniques: a 9-field technique, with nine equispaced axial beams, and a tangential beamlet technique, with three to five ipsilateral beams. The third plan (a segmental technique) used a forward-planned multisegment technique, and the fourth plan (a segmental blocked technique) was identical but included a block to limit heart dose. Dose--volume histograms were generated, and metrics chosen for comparison were analyzed using the paired t test.


RESULTS
Mean heart and left anterior descending coronary artery doses were similar with the tangential beamlet and segmental blocked techniques but higher with the segmental and 9-field techniques (mean paired difference of 15.1 Gy between segmental and tangential beamlet techniques, p < 0.001). Substantial volumes of contralateral tissue received dose with the 9-field technique (mean right breast V2, 58.9%; mean right lung V2, 75.3%). Minimum dose to ≥95% of breast PTV was, on average, 45.9 Gy with tangential beamlet, 45.0 Gy with segmental blocked, 51.4 Gy with segmental, and 50.2 Gy with 9-field techniques. Coverage of the internal mammary region was substantially better with the two beamlet techniques than with the segmental blocked technique.


CONCLUSIONS
Compared to the 9-field beamlet and segmental techniques, a tangential beamlet IMRT technique reduced exposure to normal tissues and maintained reasonable target coverage.
Jagsi
Reshma
R
Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, Michigan, USA. rjagsi@med.umich.edu
Moran
Jean
J
Marsh
Robin
R
Masi
Kathryn
K
Griffith
Kent A
KA
Pierce
Lori J
LJ
D000328:Adult; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D003331:Coronary Vessels; D005260:Female; D006321:Heart; D006801:Humans; D015182:Lymphatic Irradiation / Q000379:methods*; D015412:Mastectomy, Segmental; D008875:Middle Aged; D058958:Organs at Risk; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012119:Respiration