[Dose-volume histograms and 3-D planning in breast-saving therapy of breast carcinoma]

Improvement of the dose homogeneity in radiation treatment of the intact breast using 3D-planning and dose volume histograms.

3D-planning, including the calculation of dose volume histograms of the planning target volume, was performed on 15 patients, who underwent radiation therapy with tangential photon beams. A standard plan and 2 modified or optimized plans were evaluated. Different dosimetric parameters like maximum dose, mean dose, standard deviation and the fractional volume which receives doses from 95 to 105% of the reference dose were compared and correlated with breast size.

With increasing breast size standard planning leads to increased overdosage, both in magnitude and volume. Individual optimization by modifying weights and wedges gives no improvement in dose homogeneity, whereas a photon energy of 10 MV results in a more homogeneous dose distribution. The drawback of the higher energy is the increased underdosage of the skin.

Using the standard geometry of tangential fields the dose homogeneity cannot be improved significantly by 3D-planning, compared to our standard technique.