Studies on radiosensitivity from an epidemiological point of view - overview of methods and results

The establishment of a predictive in vitro assay for radiosensitivity has been a goal in radiotherapy research. To date, no single assay has proven to be effective for this purpose. A review of the epidemiologic methods used in the studies has been undertaken to evaluate limitations associated with specific design options and to develop recommendations for future research.

We focused on studies attempting to establish the usefulness of an assay in breast cancer patients undergoing radiotherapy using skin reactions as indicators for radiosensitivity. The 25 published studies included were evaluated with respect to criteria for good epidemiological studies: (a) study design, (b) study population, (c) assessment of radiation reaction, and (d) treatment of confounding factors.

Limitations in study design were often found among the studies reviewed. Possible sources of bias are, among others, misclassification due to non-standardized assessment of side effects, selection bias due to drawing convenience patient groups instead of representative patient groups, and confounding due to analysis not adjusted for important factors influencing the severity of side effects.

Further studies should make use of good epidemiological practice so that valid conclusions can be drawn with respect to the usefulness of an in vitro assay to distinguish between patients with different degrees of radiosensitivity in clinical practice.