Aim: Improvement of the dose homogeneity in radiation treatment of the intact breast using 3D-planning and dose volume histograms.
Patients and method: 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.
Results: 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.
Conclusion: Using the standard geometry of tangential fields the dose homogeneity cannot be improved significantly by 3D-planning, compared to our standard technique.