The Effect of Radiation Therapy on Circulating Tumor Cells and Its Impact on the Immune System in Early-Stage Breast Cancer, Depending on Patient Age

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 the biological characteristics of the tumor—including its growth rate (Ki-67 index), detectable hormone receptors 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 1–2) typically involves breast-conserving surgery with the goal of complete recovery. After surgery, further treatment (adjuvant therapy) may be administered to reduce the risk of residual disease or recurrence. Radiation therapy is one treatment option in this context. The goal is to damage any remaining cancer cells using high-energy radiation.

The goal of the CETC 002 study is to investigate how this radiation therapy affects circulating tumor cells (CETCs) in the blood and how the immune system responds to them depending on age. Patients will be divided into two groups based on their hormonal status (Group 1: premenopausal; Group 2: postmenopausal). These studies aim to improve our understanding of the fundamental molecular biological processes involved in breast cancer and to identify potential biomarkers that could help better predict the course of the disease. In the study, blood samples will be collected at various time points during and after radiation therapy. These samples will be used to analyze the tumor cells in detail, compare their characteristics with those of the original tumor cells, and observe changes in the immune system. In addition, the tumor tissue obtained during surgery will be examined for specific immunological characteristics, including so-called tumor-infiltrating lymphocytes (TILs), which indicate how the immune system is responding to the tumor. This is an observational study, which means that no new drugs or forms of therapy are being tested. The primary endpoint—that is, the focus of the study—is the effect of radiation therapy after 2 years.

Women aged 18 and older who have invasive breast cancer confirmed by a tissue sample (histologically) without spread to other organs (distant metastases) and who are receiving breast-conserving therapy with planned adjuvant radiation therapy are eligible to participate. Patients with inflammatory breast cancer, DCIS (a precancerous condition of the breast), recurrences, distant metastases, or other cancers in the past ten years are excluded. Patients who have already received radiation therapy are also ineligible to participate.