Hazard ratios in cancer clinical trials--a primer.

The increase and diversity of clinical trial data has resulted in a greater reliance on statistical analyses to discern value. Assessing differences between two similar survival curves can pose a challenge for those without formal training in statistical interpretation; therefore, there has been an increased reliance on hazard ratios often to the exclusion of more-traditional survival measures. However, because a hazard ratio lacks dimensions it can only inform the reader about the reliability and uniformity of the data. It does not provide practitioners with quantitative values they can use, nor does it provide information they can discuss with patients. Motivated by a non-scientific poll of oncologists in training and those with board certification that suggested only a limited understanding of the derivation of hazard ratios we undertook this presentation of hazard ratios: a measure of treatment efficacy that is increasingly used and often misused.