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Hybrid IMRT plans--concurrently treating conventional and IMRT beams for improved breast irradiation and reduced
Charles S Mayo1, Marcia M Urie, Thomas J Fitzgerald
1Department of Radiation Oncology, University of Massachusetts Medical School, UMASS/Memorial Medical Center, 55 Lake Avenue North, Worcester, MA 01655, USA. mayoc@ummhc.org
Purpose:
To evaluate a hybrid intensity modulated radiation therapy (IMRT) technique as a class solution for treatment of the intact breast.
Methods And Materials:
The following five plan techniques were compared for 10 breast patients using dose-volume histogram analysis: conventional wedged-field tangents (Tangents), forward-planned field-within-a-field tangents (FIF), IMRT-only tangents (IMRT tangents), conventional open plus IMRT tangents (4-field hybrid), and conventional open plus IMRT tangents with 2 anterior oblique IMRT beams (6-field hybrid).
Results:
The 4-field hybrid and FIF achieved dose distributions better than Tangents and IMRT tangents. The volume of tissue outside the planning target volume receiving > or =110% of prescribed dose was largest for IMRT tangents (average 158 cc) and least for 6-field hybrid (average 1 cc); the FIF and 4-field hybrid were comparable (average 15 cc). Heart volume > or =30 Gy averaged 13 cc for all techniques, except Tangents, for which it was 32 cc. Average total lung volume > or =20 Gy was 7% for all. Contralateral breast doses were < 3% for all. Planning time for hybrid techniques was significantly less than for conventional FIF technique.
Conclusions:
The 4-field hybrid technique is a viable class solution. The 6-field hybrid technique creates the most conformal dose distribution at the expense of more normal tissue receiving low dose.
