Single-session accelerated partial-breast radiation therapy following breast-conserving surgery for early-stage breast cancer

Breast cancer (mammary carcinoma) is a malignant disease of the breast gland tissue characterized by the uncontrolled proliferation of breast gland cells. Treatment depends on numerous factors, such as the patient’s overall health, the stage of the disease, and the characteristics of the cancer cells—in particular, the presence of detectable hormone receptors on the surface of the cancer cells (hormone receptor-positive) and the presence of the HER2 receptor (HER2-positive or HER2-negative). Following breast-conserving surgery, the entire breast is typically irradiated to reduce the risk of recurrence in the operated breast. Conventional whole-breast radiation therapy extends over several weeks and involves numerous radiation sessions. In recent years, studies have shown that for patients with a low risk of recurrence, accelerated partial-breast irradiation (APBI)—in which only the tissue surrounding the former tumor bed is specifically irradiated—could also be an effective alternative. As part of the GEC-ESTRO research group, this procedure has been gradually refined, and the treatment time has been reduced from the original four to five days to two days and, ultimately, to a single session. Previous studies involving three to four radiation sessions over two days have shown good results in terms of tumor control and tolerability.

The aim of this Phase 2 study is to investigate whether a further reduction to a single radiation session is safe and well-tolerated. The radiation is delivered as internal radiation therapy (brachytherapy) via thin hollow needles (multicatheters) that are inserted into the breast tissue around the former tumor bed and deliver the radiation directly to the target area. Since this is an uncontrolled study without a comparison group, all patients receive the same treatment. The primary objective of the study is to assess the incidence of late side effects over a five-year period. In addition, the recurrence rate, overall survival, cosmetic outcomes, and the patients’ quality of life will be assessed over five years.

Women aged 40 and older with early-stage breast cancer (up to Stage 2, tumor size less than 3 cm, no distant metastases) are eligible to participate in this study. Breast-conserving surgery with complete removal of the tumor must have been performed. If the breast cancer is HER2-positive, systemic anti-HER2 therapy must have been administered.