Dosimetric comparison of left-sided whole breast irradiation with 3DCRT, forward-planned IMRT, inverse-planned IMRT, helical tomotherapy, and topotherapy.

BACKGROUND AND
PURPOSE: To compare left-sided whole breast conventional and intensity-modulated radiotherapy (IMRT) treatment planning techniques.
MATERIALS AND METHODS: Treatment plans were created for 10 consecutive patients. Three-dimensional conformal radiotherapy (3DCRT), forward-planned IMRT (for-IMRT), and inverse-planned IMRT (inv-IMRT) used two tangent beams. For-IMRT utilized up to four segments per beam. For helical tomotherapy (HT) plans, beamlet entrance and/or exit to critical structures was blocked. Topotherapy plans, which used static gantry angles with simultaneous couch translation and inverse-planned intensity modulation, used two tangent beams. Plans were normalized to 50Gy to 95% of the retracted PTV.
RESULTS: Target max doses were reduced with for-IMRT compared to 3DCRT, which were further reduced with HT, topotherapy, and inv-IMRT. HT resulted in lowest heart and ipsilateral lung max doses, but had higher mean doses. Inv-IMRT and topotherapy reduced ipsilateral lung mean and max doses compared to 3DCRT and for-IMRT.
CONCLUSIONS: All modalities evaluated provide adequate coverage of the intact breast. HT, topotherapy, and inv-IMRT can reduce high doses to the target and normal tissues, although HT results in increased low doses to large volume of normal tissue. For-IMRT improves target homogeneity compared with 3DCRT, but to a lesser degree than the inverse-planned modalities.