Comparison of 3D-Conformal Planning Using Partially Wide Tangents and Direct Photon/electron Portals for Breast Radiotherapy with Internal Mammary Nodes Inclusion: A Dosimetric Analysis

Background: Internal mammary lymph nodes (IMNs) are a potential site of metastasis for breast cancer. Targeting IMNs as part comprehensive regional nodal irradiation comes at the cost higher unwanted doses to critical nearby organs risk. Thus, efficacy and safety different radiotherapy techniques coverage this area remain elusive. Objectives: We present dosimetric comparison between partially wide tangents (PWT) direct photon/electron (P/E) portals in terms target volume normal tissue sparing. Methods: Patients with left-sided cancer, who were referred our clinic post-lumpectomy or post-mastectomy radiotherapy, underwent computed tomography (CT) simulation. The left IMNs, heart, lung, right breast, esophagus contoured. Dosimetric comparisons based on dose-volume histograms (DVHs) generated all aforementioned organs. A subgroup analysis was also performed patients’ type surgical treatment. Results: total 30 patients (10 conserving surgery 20 modified radical mastectomy) included. P/E plan provided (P-value CTV V105%: < 0.001) P-value 0.087 regarding mean dose received by less heart Heart V30Gy: 0.021), lungs Lung V20Gy: 0.003) irradiated. However, these advantages came more hotspots compared PWT technique. Conclusions: technique had toxicity regardless surgery. Based results study, overall, portal is superior cancer internal node inclusion. appropriate treatment should be decided case-by-case basis.