3D tangential wedge pair radiotherapy planning versus 3D forward planned IMRT for breasts in the reduction of hot spots and cardiac doses. (A feasibility study)

Radiotherapy plays an important role in the treatment of Breast Cancer and thus far wedged Tangential pairs (WTP) is accepted as the gold standard. However due to greater knowledge of side effects, an interest for increased homogeneity and protection of the Heart has increased. Step and shoot IMRT (S&S) is thought to be the key to this.PurposeTo compare 3D WTP against S&S plans for Breast Radiotherapy.MethodFor a feasibility study, analysis was carried out on five CT Breast data sets. The data was copied and anonymised and were retrospectively planned, firstly by WTP, and secondly by S&S. The two techniques were compared via Dose Volume Histograms (DVH).ResultsWhen comparing V95 averages the TWP gave 97.4% coverage versus 96.2% for S&S, For V105, V110 and V115 volumes were recorded as18%, 5%, and 0.2% respectively for TWP, and 7% V105, and 0% V110 and V115 for S&S. Comparison of OAR doses revealed, on average Lung V20, V5 and Heart V13 of 4.6%, 7.6% and 1.18% respectively for TWP and. 4.2% (V20), 7.4% (V5) and 0.08% for Heart V13 for S&S.ConclusionsFor V95 and hot spots the S&S planning method proved more consistent and did not yield extra dose to the lungs. In both of the planning methods the Heart received dose reduction lower than anticipated. Partially this is envisaged to be due to contouring issues and the inclusion of OARs in the defined fields. The small sample size may have also contributed to these lower than expected reductions, nevertheless any method which offers a reduction, however small, should be offered.