(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: report the intensity modulated proton therapy planning techniques implemented on 82 breast cancer patients treated at a proton therapy center from January 2018 to February 2020.
Methods: plans were created using 1 or 2 en-face beams for unilateral breast or chest wall target volume with regional nodes (IM, SCV and AX); 3 or 4 beams for bilateral chest wall with nodes. To control the degree of modulation, simple single-field optimization (S-SFO) and hybrid SFO (H-SFO) were mainly used. For S-SFO, each field delivers a uniform dose to the entire volume. For H-SFO, one field delivers a uniform dose to a portion of the target volume, and in between the fields, a gradient junction is created. The junction can be along superior-inferior direction where the SCV was treated with an anterior(ish) beam, and the lateral oblique beam was avoided not to treat through shoulder and skin folds. For the rest of the target volume, both SFO beams were used. The junction can also be along medial to lateral direction, where medial and lateral portion of the target volume is treated by an anterior beam and a lateral oblique beam, respectively. The longitudinal and transverse junctions can be used simultaneously depending on the patient anatomy.
Results: and 2 fields were used for 18 and 61 patients, respectively; 3 and 4 fields were used for 2 and 1 bilateral chest wall patients. S-SFO and H-SFO plans were used for 53 and 28 patients, respectively. Only 1 patient was treated with MFO. For H-SFO, longitudinal, transverse and both junctions were used for 12, 2, and 14 patients. Average heart mean dose and lung V20Gy is 0.7Gy and 12.2%.
Conclusion: implemented S-SFO and H-SFO techniques maximize the control of field modulation, which yield an optimal robustness and dosimetric benefits tailored to individual patient’s anatomy.
Keywords
Intensity Modulation, Protons, Breast
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