Abstract PO5-22-03: Influence of the surgical clip concerning the dose and volume of irradiated surrounding tissues including lung and heart in the planning of radiotherapy boost with conservative breast surgery with and without oncoplasty
Authors: Freitas Nilceana , Watanabe Priscila , Paiva Jean , Bezerril Carolina , Valentim Marcelo , Gontijo Thais , Araujo Flavia , Freitas-Junior Ruffo 
Published: May 2024

Introduction: Patients with the highest risk of breast cancer undergoing conservative surgery receive an additional boost dose of radiotherapy in the tumor bed during treatment planning, which is known to bring benefits in local control. Objectives: To evaluate the influence of the surgical clip concerning the volume of surrounding tissues irradiated during radiotherapy, in patients submitted to conservative breast surgery with and without oncoplasty. Materials/Methods. The analyzed variables were defined as: the volume of the boost (V100 Boost) and breast tissue (V100 Breast) that received 100% of the prescribed dose during the radiotherapy planning and the volume of the heart (V40 Heart) and lung (V40 Lung) that received 40% of the prescribed dose during the boost phase in patients undergoing treatment with breast conservation. The variables were compared about the insertion or not of the surgical clip and the influence of oncoplastic surgery on the volume of irradiated tissues of the breast, boost, heart and lung during radiotherapy planning. Student's t-test (95%CI; p&lt; 0.05) was used to compare mean volumes as a function of the presence or not of surgical clips and oncoplastic surgery. Results: Retrospective study included 183 women with breast cancer who underwent treatment with conservative breast surgery and radiotherapy of the whole breast, followed by sequential boost, between January 2011 and January 2021. Boost, breast, heart, and lung volumes were evaluated during planning for conformational radiotherapy. The results showed a significant difference between the average boost volumes when the patient was clipped. The average boost volume that received 100% of the prescribed dose was V100 Boost=244.22cm³ (SD±158) in the absence of the clip. In the presence of 1 or 2 clips, this average was V100 Boost= 94.87cm³ (SD±37) and with 3 or more clips it was V100 Boost= 96.99cm³ (SD±39) (p&lt; 0.001). There was also a significant difference in mean breast volumes that received 100% of the prescribed dose. In the absence of the clip, the V100 Breast=373.16 cm³ (SD±222) and when 1 or 2 clips were present, the V100 Breast=235.28 cm³ (SD±125) (p=0.01). The analyzes of the mean volumes of the heart (V40 Heart) and lung (V40 Lung) that received 40% of the prescribed boost dose were not statistically significant, regardless of the presence and number of clips. For the oncoplasty group, there was no statistical difference between the means of boost, breast, heart and lung volumes. Conclusion: The presence of the surgical clip reduced the volume of the boost and the breast that received 100% of the dose in the radiotherapy planning. The volume of the boost (V100 Boost), which received 100% of the dose prescribed during radiotherapy planning, was smaller in patients with a surgical clip, as was the volume of irradiated breast tissue (V100 Breast) in clipped patients. The volume of irradiated tissue in the heart (V40 Heart) and lung (V40 Lung) that received 40% of the prescribed dose during the boost phase in radiotherapy planning did not suffer statistical differences in insertion or not of the surgical clip. Oncoplastic surgery and the presence of surgical clips did not influence the volumes of irradiated boost, breast, heart and lung tissues during the radiotherapy planning of patients undergoing conservative surgical treatment of the breast. Table: Means of boost, breast, heart and lung irradiated volumes according to the presence or absence of clips and oncoplastic surgery

Table. Means of boost, breast, heart and lung irradiated volumes according to the presence or absence of clips and oncoplasty surgery Variable (cm3) Clip p valor Oncoplasty p valor With Without With Without Means Means Means Means V100% Boost 94 244 &lt; 0,001 102 118 0,906 V100% Breast 235 373 0,01 271 272 0,816 V40% Heart 1,10 4,52 0,33 1,96 1,39 0,903 V40% Lung 56,66 56,10 0,93 51,63 52,53 0,796

Citation Format: Nilceana Freitas, Priscila Watanabe, Jean Paiva, Carolina Bezerril, Marcelo Valentim, Thais Gontijo, Flavia Araujo, Ruffo Freitas-Junior. Influence of the surgical clip concerning the dose and volume of irradiated surrounding tissues including lung and heart in the planning of radiotherapy boost with conservative breast surgery with and without oncoplasty [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-22-03.