In Vitro Perspective on Hypofractionated Radiotherapy in Breast Cancer

Breast cancer remains a major global health challenge, with treatment access further constrained during the COVID-19 pandemic, particularly in resource-limited settings. This study evaluates the in vitro effects of hypofractionated versus conventionally fractionated radiotherapy on three breast cell lines: MCF-7 (oestrogen receptor-positive, ER+/PR+), MDA-MB-231 (triple-negative: ER−/PR−/HER2−), and MCF-10A (non-tumorigenic mammary epithelial). Cells were exposed to cobalt-60 γ-rays, and radiobiological endpoints assessed included clonogenic survival, α/β ratios, adaptive responses, migration, invasion, and cytotoxicity through lactate dehydrogenase assays. The α/β ratios ranged from 2.5 to 5.4 Gy across breast cancer subtypes. Hypofractionation reduced survival in hormone receptor-positive cells, whereas triple-negative cells exhibited increased survival. Adaptive radiation responses enhanced viability across all cell lines, while non-cancerous MCF-10A cells demonstrated reduced migration following treatment. These findings suggest that hypofractionated radiotherapy may be beneficial in hormone receptor-positive breast cancer, while triple-negative disease may show a trend toward different responses, although this was not statistically significant (MDA-MB-231, p = 0.290). The results underscore the importance of tailoring fractionation strategies to breast cancer subtype and highlight the translational potential of preclinical radiobiology in guiding personalised radiation oncology approaches.