Study Comparing Precision Radiation Therapy During Surgery to Full-Breast Radiation Therapy for Early-Stage Breast Cancer

Breast cancer (mammary carcinoma) is a malignant disease of the mammary gland tissue characterized by the uncontrolled proliferation of mammary gland cells. Treatment of the disease depends on numerous factors, such as the patient’s overall health, the stage of the disease, and, in particular, certain biological characteristics of the tumor, such as its growth rate (Ki-67 index), detectable hormone receptors (HR) on the surface of the cancer cells (estrogen receptor-positive, progesterone receptor-positive), and the increased presence of HER2 receptors on the cells (HER2-positive).

Treatment for early-stage breast cancer (stages I–II) typically involves breast-conserving surgery with the goal of complete recovery. To reduce the risk of the disease returning, drug therapy is administered before surgery in certain cases to shrink the tumor (neoadjuvant). In many cases, and depending on certain risk factors, further therapy may be administered after surgery (adjuvant) to reduce the risk of residual disease or recurrence, e.g., through radiation therapy. The cancer cells are damaged by high-energy radiation. In this procedure, the affected breast is fully irradiated from the outside (percutaneously). To avoid excessive damage to the surrounding tissue, such as the skin, this form of radiation therapy is administered in several sessions. Another treatment option is intraoperative radiation therapy (IORT), in which the tumor region is irradiated once during the surgical procedure. To do this, after the tumor has been surgically removed, a special radiation probe is inserted directly into the tumor region, and the radiation dose is delivered directly to the tumor bed. The wound is then closed. IORT is approved in Germany for small, hormone receptor-positive tumors if they are detected at an early stage and there is no lymph node involvement. Targeted irradiation of the tissue and a lower total radiation dose may potentially reduce the occurrence of side effects.

The aim of this study is to investigate whether single-session intraoperative radiation therapy can be a suitable alternative to the standard whole-breast radiation therapy following surgery. As part of the study, patients are randomly assigned to two groups. The control group receives the standard whole-breast radiation therapy after surgery over 3 weeks (15 sessions), and the study group receives a single dose of intraoperative radiation during the surgical procedure. The researchers responsible for analyzing the study data are blinded; that is, they do not know which group the patients belong to. The primary endpoint of the study is the presence and severity of fatigue (pathological weakness) after 12 weeks. Follow-up as part of the study will continue for up to 5 years.

Eligible participants are women aged 50 and older with small, hormone receptor-positive, HER2-negative breast cancer (less than 2.5 cm), without affected lymph nodes and without prior chemotherapy, anti-hormone therapy, or radiation therapy. Excluded are, among others, patients with more aggressive tumors (G3), invasive lobular carcinoma, notable microcalcifications, or other relevant pre-existing conditions.