Radiotherapy plays a vital role in the management of breast cancer, providing significant benefits in both early and advanced stages of the disease. This treatment modality utilizes high-energy radiation to target and destroy cancer cells while minimizing damage to healthy surrounding tissues. In this article, we will explore the various aspects of radiotherapy in breast cancer, including its indications, techniques, benefits, and potential side effects. Breast cancer is the most common cancer among women worldwide, and radiotherapy is frequently employed as a component of the comprehensive treatment approach. It can be used in different settings, including after breast-conserving surgery (lumpectomy) or mastectomy, depending on the stage and characteristics of the tumor. The primary goal of radiotherapy is to eradicate any remaining cancer cells in the breast or regional lymph nodes, reducing the risk of recurrence and improving overall survival rates. The radiotherapy process typically begins with a thorough evaluation and planning phase. During this stage, imaging techniques, such as computed tomography (CT) scans, are used to precisely map the tumor and surrounding tissues. This helps determine the optimal radiation dose and target volume. The treatment plan is then carefully designed, taking into account factors like tumor size, location, and biological characteristics. External beam radiotherapy (EBRT) is the most common technique used in breast cancer treatment. It involves delivering radiation to the affected area from an external source, such as a linear accelerator. EBRT can be administered in various ways, including whole-breast irradiation, partial breast irradiation, or regional nodal irradiation. The duration of treatment may vary, but it typically lasts several weeks, with daily sessions of a few minutes each. Radiotherapy in breast cancer offers several significant benefits. It significantly reduces the risk of local recurrence by destroying any remaining cancer cells after surgery. Studies have shown that adjuvant radiotherapy can decrease the recurrence rate by up to 70%. Furthermore, radiotherapy has been shown to improve overall survival rates, especially in patients with certain high-risk features, such as larger tumor size, positive lymph nodes, or younger age. Despite its effectiveness, radiotherapy can also have side effects, although they are generally temporary and manageable. Common acute side effects may include fatigue, skin irritation or redness, and temporary breast swelling or tenderness. Long-term effects can include changes in breast appearance, such as fibrosis or shrinkage, and, rarely, damage to the heart or lungs. However, modern techniques, such as intensity-modulated radiation therapy (IMRT) or proton therapy, aim to minimize these risks by precisely targeting the tumor while sparing healthy tissues. In recent years, advancements in radiotherapy technology have further improved treatment outcomes. Image-guided radiation therapy (IGRT) allows for real-time visualization of the tumor during treatment, enabling accurate delivery of radiation. Stereotactic body radiotherapy (SBRT) delivers high doses of radiation in a few sessions, reducing treatment duration and improving patient convenience. These innovations contribute to better outcomes, higher treatment precision, and improved quality of life for breast cancer patients. In conclusion, radiotherapy is an integral part of the multidisciplinary approach to breast cancer treatment. By effectively targeting and eliminating cancer cells, it reduces the risk of local recurrence and improves overall survival rates. Although it can have side effects, they are generally manageable and temporary. With the advancement of technology, radiotherapy techniques continue to evolve, offering improved precision and reduced treatment duration. Through ongoing research and innovation, radiotherapy continues to play a crucial role in the fight against breast cancer, providing patients with better outcomes and a brighter future.