title: A likelihood ratio test for cancer screening trials.
abstract: In randomized cancer screening trials, mortality rates for the screened group relative to those of the control group are not likely to be constant as a function of years from randomization due to the inherent lag between initiation of screening and any putative effects of screening on mortality. In this situation, a log rank test for differences in mortality between the randomization groups will not be optimal. Although optimality could potentially be recovered by use of a weighted log rank statistic, the optimal weights are difficult to specify a priori and the potential loss of power by use of poorly specified weights is great. We describe a likelihood ratio test with two degrees of freedom for use in this situation which is based on a fit of a weakly structured full model. Computation of an approximate significance level for this test is described and a large sample justification for this approximation is given. Size and power properties of the proposed statistic are compared to that of several other statistics in a small simulation study and the statistic is applied to data from the HIP Breast Cancer Screening Trial.
authors.affiliation: Fred Hutchinson Cancer Research Center, Seattle, Washington 98104, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Self
authors.forename: R
authors.initials: R
authors.lastname: Etzioni
mesh_terms: D001699:Biometry / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D015233:Models, Statistical; D009369:Neoplasms / Q000401:mortality / Q000628:therapy*; D011336:Probability; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D016019:Survival Analysis; D013997:Time Factors