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Purpose To design and implement a new protontherapy planning method for the treatment of shallow lesions with PBS and to compare it to the standard method. Methods In order to treat tumors located at depths lower than our minimum range available (4.1 cm), a pre-absorber is needed (Range Shifter – RS). The RS also causes scatter, so it is associated to some dose degradation, which should be minimized. We studied three tumor localizations (pelvic, H&N and Cranio-Spinal-Irradiation) requiring RS and we created three plans for each case: one is the standard method with the RS always used as close as possible to the patient, one with the RS used only for the shallow part of the tumor but completely retracted (Figure a) and the third as the second but with the RS as close as possible to the patient (Figure b). We called these last two Range Shifter Optimization (RSO) techniques. We compared those plans in terms of dose distribution quality, delivery time and patient QA results. Results In tables dosimetric results and delivery time are reported. A very good sparing of OARs are obtained when the RSO technique is used with the RS extended toward the patient with no significative loss in terms of target coverage. Patient QA gave very good results in terms of γ Passing Rate (PR) (3%,3 mm) for both RSO techniques (mean 98.09%, minimum 93.75%) while the standard had some very low PR (minimum 81.09%) while the average was still good (97.73%). The delivery time increased but was still acceptable in terms of patient compliance. Conclusions We developed a new planning technique for shallow lesions and we demonstrated its superiority (plan quality and patient specific QA results) with respect to the standard method. This technique is now routinely used to treat patients in our centre. [ABSTRACT FROM AUTHOR]

Purpose Proton therapy reduces lung dose and mean heart dose in breast cancer irradiation in adjuvant breast cancer, in particular with nodal involvement [1]. In this work we compare 10 selected intensity modulated photon therapy (IMXT) treatment cases selected from the sending institution with PBS proton therapy. Methods and materials The eligibly criteria of the sending institution were: poor coverage of the target volumes, unfavourable dose volume histograms (DVH) to the organs at risk (OAR) lung and heart or wide irradiated volume (IV) with static IMXT. The type of case were heterogeneous as shown in Table 1. All plans were performed on the CT and volumes send applying a class solution of 3 proton field with range shifter with treatment planning system (TPS) Raystation. All plans were performed in robust Single Field Optimization technique (rSFO) optimizing the target and the OAR heart and the ipsilateral lung. The optimization was done with clinical pencil beam algorithm and 5 mm geometrical robust optimization tool provided by the TPS. No robust optimization of the range was applied. Results Comparing the proton and photon plans there was a significant improvement in at least one of the following parameter: IV, DVH of lung, DVH of heart for each case (e.g. Fig. 1). Conclusion The results of this study are promising. The heuristic eligibility method provide positive answer in 100% of the cases. Further work are necessary to assess role of range errors of proton peak. [ABSTRACT FROM AUTHOR]