The Utility of Intraoperative Radiotherapy in Breast Cancer (RIOMA) is an observational project to understand the use and outcomes of intraoperative radiotherapy in patients with breast cancer under conditions of clinical use (not clinical trials). Intraoperative radiotherapy (IORT) is a technique that began to be used years ago, transferring the patient from the operating room to the radiotherapy suite. This technique therefore fell into disuse. The emergence of miniaturized linear accelerators has led to a resurgence of IORT, especially as part of conservative treatment in patients with breast cancer, both as a booster or as a sole treatment (partial breast irradiation).

This project is based on an online platform. Each participating center will be assigned access codes on the website to access and complete the coded clinical data for each patient treated with intraoperative radiotherapy. Data on tumor characteristics, the type of intraoperative radiotherapy, follow-up, complications, and cosmetic outcomes are included.

Primary objective:

To understand the characteristics of patients treated with intraoperative radiotherapy under routine clinical practice conditions.

The project is based on structured data collection in an electronic data collection notebook (using the OpenclinicaTM standard), relating to the care provided according to standard clinical practice in the Radiation Oncology, Gynecology and Surgery departments of the participating centers in Spain.

Inclusion Criteria:

• Patients with breast cancer who are candidates for intraoperative irradiation exclusively
• Patients with breast cancer who are candidates for intraoperative irradiation combined with external beam irradiation
• Patients with recurrence of breast cancer who are candidates for intraoperative irradiation
• Have read the information sheet and signed the informed consent form -

Exclusion Criteria:

• Patient's that express wish not to participate.

Patients with early breast cancer who are candidates for intraoperative radiotherapy, such as exclusive partial irradiation, anticipated boosting, or salvage after a second conservative surgery.