A Narrative Review of Cancer Risks in Medical Radiation Workers Across High- and Low-Dose Practice Eras: Implications for Radiation Protection.

Medical radiation workers constitute the largest occupational group exposed to man-made ionising radiation, yet much of the evidence on cancer risk derives from early high-dose practice eras that differ substantially from contemporary conditions. This narrative review synthesises evidence from cohort studies of medical radiation workers across occupational exposure eras, with emphasis on epidemiologic approaches, observed cancer risk patterns, and sex-specific differences. Epidemiologic methods have evolved from proxy-based exposure indicators to quantitative dose-response modelling using excess relative risk, supported by improved dosimetry and organ-dose reconstruction. Early high-dose cohorts consistently demonstrate elevated risks for radiosensitive cancers, including breast cancer, haematopoietic malignancies, and non-melanoma skin cancer. In contrast, contemporary cohorts exposed under current protection standards accumulate low cumulative doses and show small, often non-significant dose-response estimates with wide confidence intervals. These findings reflect both reductions in occupational exposure and the limited statistical power of epidemiologic studies at low dose levels, where excess risks are difficult to detect and dose-response shape cannot be clearly distinguished. Available evidence does not indicate consistent sex-based differences in radiation-related cancer risk at occupational exposure levels. Overall, while advances in dosimetry have improved exposure assessment, the ability to quantify cancer risk under contemporary low-dose conditions remains constrained. The findings support the effectiveness of current radiation protection practices while highlighting persistent uncertainty in estimating risks at low occupational doses.