Age dynamics of cancer incidence intensity indicates existence of some frailty subgroups

The problem of managing population and occupational risks of cancer incidence or mortality presupposes knowledge on biological mechanisms of their formation. These mechanisms determine dynamics of mass processes recorded by statistics. However, there is still no clear understanding of the causal relationship between possible factors of cancer incidence and its real dynamics. The article analyzes a hypothesis about significant influence on dynamics of incidence rates between ‘health’ and ‘disease’ states exerted by an intermediate transitional and objectively existing ‘frailty’ state, which is characterized by accelerated withdrawal from observation compared with the intensity associated with the general variability of individual properties of a population. It has been statistically established that the dynamics of such common diseases as stomach cancer, lung cancer, breast cancer, prostate cancer, and thyroid cancer can be explained by the fact that almost all diagnosed cases are observed after an individual enters a vulnerable group long before the diagnosis itself. From this point of view, two fundamentally different biological mechanisms of occurrence of neoplasms should be distinguished: induction as a transition from the state of ‘health’ to the state of ‘frailty’, as well as promotion as a transition from ‘frailty’ to ‘disease’. Each of these transformations should be characterized in a population by their intensity and their dependence on endogenous or exogenous risk factors. It is shown that some known facts of paradoxical changes in radiosensitivity indicators can be satisfactorily interpreted within the concept of a frailty subgroup by using numerical modelling on the example of modifying the dynamics of thyroid cancer incidence under influence of ionizing radiation. The facts were established in 1994–2006 and have not yet received a proper explanation since the concept discussed by the authors of the studies has not been involved.