TP53 and cancer: Begg and Zhang showed that the odds ratio (OR) for smoking on p53+ status from the case-only design, θCase-Only, was equivalent to the ratio of two case-control ORs for smoking estimated from a full case-control study: the OR when p53+ cancer cases were compared to controls, θ1, and the OR when p53- cancer cases were compared to controls, θ2.[1] That is, θCase-Only = θ1/θ2.