Methods are given for the comparison of two treatment groups in experiments giving rise to multiple tumors. Methods based on the gaps in time between successive tumors are emphasized, but, for comparison, one method based directly on times to tumor is also presented. When applied to the results of an experimental animal carcinogenesis study, these analyses show that a diet supplemented with retinyl acetate reduces the hazard of mammary tumors, compared with controls, in every gap, and they allow one to combine evidence from the several gaps to obtain a powerful test for treatment effect.
Red blood cell (RBC) and platelet (PLT) transfusion requirements during the first 13 weeks after HLA-identical marrow transplantation were studied in 82 patients with aplastic anemia. On the average, patients were given 9 units of RBCs (1-82) and 44 units of PLTS (6-468). The greatest need for support was during the first 4 weeks postgrafting. A multivariate statistical analysis of 22 variables showed that RBC and PLT requirements increased with age. In addition, RBC requirements increased if the patient had isohemagglutinins against the marrow donor's RBC, i.e., if the marrow transplant was across a major ABO barrier.
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