Future directions of radiation therapy in the management of breast cancer

: Over the past several decades, radiation therapy has played a key role in the management of breast cancer. Although the oncologic benefits of radiotherapy are well established, the landscape of breast oncology is ever changing and evolving, and radiation is no exception. Radiation oncologists are pursuing new technology and techniques to maintain their oncologic benefits, while minimizing potential side effects and treatment burden. This has led to clinical trials using therapy de-escalation of radiation in select patients with favorable characteristics. Multiple studies are using modern genetic testing, such as Oncotype Dx and PAM50, to identify low-risk women that may potentially have radiation omitted in favor of endocrine therapy alone. Another area of active investigation is the de-escalation of therapy in node-positive patients, using genetic testing or response to neoadjuvant systemic therapy as prognostic factors. The use of hypofractionation has become standard of care in the breast conservation setting, but its use in the post-mastectomy is an area of interest in multiple ongoing studies. Partial breast irradiation (PBI) is another evolving avenue to shorten treatment time, with multiple modalities available. Other investigators are attempting to alter the traditional treatment paradigm of breast cancer by administrating radiation in the preoperative setting rather than postoperative. New technologies such as proton therapy and stereotactic body radiation therapy (SBRT) have made their way into ongoing trials as well. In the setting of oligometastatic breast cancer, several trials are attempting to use SBRT as metastasis directed therapy to improve oncologic outcomes. In this review, we cover several ongoing important breast radiation clinical trials and how they will impact breast cancer care.