Effect of radiobiological parameters on the TCP for breast cancer radiotherapy

Breast cancer remains the most prevalent malignancy affecting women globally. Among the various treatment modalities, radiotherapy stands out as a cornerstone for tumor eradication. This research explores the impact of radiosensitivity parameters on Tumor Control Probability (TCP) in breast cancer, with an emphasis on distinct radiotherapeutic techniques such as conventional, hypofractionated, and FAST, as well as the role of tumor repopulation. Based on the literature review, we obtained data on α and β radiosensitivity parameters, cell repopulation rates and standard breast cancer treatment protocols. These parameters informed the calculation of the fraction of cells surviving irradiation via the linear-quadratic model, facilitating an assessment of treatment efficacy through the Poissonian TCP model. Our findings underscore the critical influence of radiosensitivity parameters α and β on treatment outcomes, with β emerging as the predominant factor due to its quadratic contribution to the survival fraction. Moreover, our analysis indicates that tumor growth is negligible relative to the substantial cell mortality induced by radiation in the case of breast cancer. Techniques such as FAST and hypofractionated radiotherapy were identified as particularly effective, offering expedited tumor control, especially with elevated α and β values. The quadratic term β significantly enhances treatment success, while tumor repopulation exerts minimal influence on TCP, corroborating previous model comparisons. Notably, higher doses per fraction, rather than increased cumulative doses, were associated with improved TCP, providing a critical insight for optimizing radiotherapy protocols. Currently, radiobiology is not systematically integrated into clinical practice, and its analysis through PCT optimizes radiotherapy treatments, improving patient quality of life and healthcare delivery.