Comparison of CT-volumed supraclavicular fossa radiotherapy planning and conventional simulator-planned defined by bony landmarks for early breast cancer

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AIM: A comparison of techniques, CT planning of the supraclavicular fossa and field based simulation. We highlight CT planned SCF radiotherapy which would be useful for a centre introducing the technique. BACKGROUND: Development of radiotherapy technique includes a move from field-based simulation to CT planning. MATERIALS AND METHODS: We conducted a retrospective review of the first 50 patients receiving radiotherapy according to the 3D CT planning protocol. Production of the previous field based technique, by virtual simulation methods on the same 50 patient CT data sets allowed both techniques to be compared for beam energy, field size, planning target volume (PTV) minimum and maximum, mean doses, depth dose normalisation, V40% lung volume and brachial plexus. RESULTS: 88% CT-volumed plans received mean dose within ICRU recommended limits compared with only 8% using previous conventional technique. 76% required 10 MV to improve coverage and one patient (2%) an opposed posterior field. The mean normalisation depth was 4.5 cm (range 1.9-7.7 cm) compared with pre-set 3 cm of the conventional technique. With CT-volumed technique the whole lung volume exposed to V40%, including the tangential fields, reduced from 10.79% to 9.64% (p < 0.001) but the mean maximum brachial plexus dose increased from 48.9 Gy to 51.6 Gy (p < 0.001). CONCLUSIONS: Dose coverage of the SCF PTV was greatly improved for plans produced from 3DCT volumes compared to field based techniques.

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