This is a prospective, registry study that will enroll all women with early stage breast cancer who will be treated with intraoperative radiotherapy (IORT) during breast-conserving surgery. The purpose of this study is to further validate the long-term effectiveness and safety of this treatment method. We aim to assess short and long-term patient outcomes associated with IORT, including perioperative complications, local and distance disease recurrences, as well as disease-free survival and overall survival.

At Providence Saint John's Health Center, there is the ongoing integration of Intra-Operative Radiation Therapy (IORT) as a standard treatment option among Breast Conserving Therapy (BCT) for individuals with in situ and early stage breast cancer. Currently, approximately 60 women per year are being treated with IORT. No repository of information of patient outcomes with this treatment has been established. This leaves a critical gap in the ability to assess the long-term outcomes of patients treated with IORT.

As the practice of using IORT to treat early stage and in situ breast cancer continues to grow at Providence Saint John's Health Center, this registry will provide the data needed to compare patient outcomes with those being treated with the traditional whole breast radiation therapy. In addition, the Providence Health & Services strives to improve patient care and outcomes with excellence whenever possible. The registry will provide the data needed to compare patient outcomes to national and community standards that can inform internal practice patterns and contribute to advancing breast cancer care nationally and internationally.

Inclusion Criteria:

• Clinical stage Tis, T1, or T2(≤ 3cm), N0, M0 (AJCC Classification)
• Unifocal Disease
• Candidate for breast-conserving surgery
• Recommended treatment by multidisciplinary team

Exclusion Criteria:

• Clinical stage T3-4, N1-3, M1
• Multifocal disease

Any individual aged ≥ 18 years with early stage breast cancer who is determined to be suitable candidates for breast-conserving surgery and IORT by a multidisciplinary team.