Improvement of Dosimetry Planning in 3D Conformal Radiotherapy for Breast Cancer With Lymph Nodes Using the High‐Tangential Tilted‐Supraclavicular Technique

Purpose Despite the emergence of advanced radiotherapy techniques such as volumetric modulated arc therapy (VMAT), three‐dimensional conformal radiotherapy (3DCRT) continues to be used due to its advantages in treating breast cancer. This study aimed to optimize the 3DCRT technique for breast cancer cases that require lymph node irradiation. Methods and Materials A total of 100 consecutive patients were included. For the first 50 patients, standard (ST) 3DCRT dosimetry plans were prepared. For the remaining 50 patients, plans were generated using an optimized High‐tangential Tilted‐supraclavicular (HT) technique, which consists of tilting the supraclavicular beam to reduce ipsilateral lung irradiation; raising the tangential fields superiorly to enhance coverage of axillary levels I and II; and intentionally creating an internal overlap between the supraclavicular and tangential fields. This overlap was resolved using the field‐in‐field (FIF) technique, primarily applied to the supraclavicular field, which is the main contributor to ipsilateral lung dose in this region. Results The HT technique demonstrated promising results compared with the ST technique and other published 3DCRT methods. It achieved improved coverage of axillary levels I and II while reducing the dose to the ipsilateral lung. However, further adjustments are needed to enhance coverage of axillary level III, the supraclavicular region, and internal mammary nodes (IMN). These include the following: completing targets contouring prior to dosimetry planning to enable precise field adjustments; relaxing the 2 cm constraint on ipsilateral lung irradiation by tangential fields when IMN is included; relaxing the maximum dose constraint for the supraclavicular and IMN fields; and using a fully electron‐based field instead of a mixed electron‐photon technique for IMN dedicated field. Conclusions The HT technique was quantitatively validated, and a modified version was proposed and qualitatively assessed. This new version may be considered for clinical use, and comparison with VMAT in a larger patient cohort is recommended.