Ellis L, et al. - In view of the fact that the addition of the mortality-to-incidence ratio (1-M/I) has been increasingly portrayed as a surrogate for cancer survival, researchers have addressed why this is mistaken in principle and misleading in practice. National cancer incidence, mortality and survival data were used in England to contrast trends in both the 1-M/I ratio and net survival at 1, 5, and 10 years for 19 cancers in men and 20 cancers in women over the 29-year period from 1981 to 2009. For only 12 of the 39 cancer/sex combinations studied, the absolute difference between the 1-M/I ratio and 5-year net survival in 2009 was less than 5%. The 1-M/I ratio varied from 5-year net survival by at least 15% for an additional 12. Findings revealed that there is no theoretical basis for the 1-M/I ratio as a proxy for the survival of cancer. For practice, either at 5 years or at any other time interval after diagnosis, it is not a valid proxy for cancer survival. It has none of the beneficial properties of an estimation of population-based survival. It should not be used as a substitute for the survival of cancer.