br Keywords life expectancy population based
Keywords: life expectancy; population-based cancer registry; relative survival; cancer; cancer survivors; Italy
Life expectancy (LE), the average number of years a homogeneous group of individuals is expected to live at a certain age, is a widely used indicator in demographical analysis [1,2]. It depends on the complete mortality profile observed in the considered population group, but not on the 2-NBDG of the population; it is therefore useful as a standardised indicator when comparing overall mortality patterns among different populations. The comparison of patients’ LE with respect to their cancer-free peers is a straightforward indicator of the disease burden; it provides “real-world” estimations for the actual impact of cancer on the population of interest and conveys what a cancer diagnosis entails in terms of future life perspectives. Differences in LE with respect to cancer-free peers are also more intuitive concepts with respect to relative survival to express at the personal level the life-threatening implications of the disease [3,4].
Most estimates of cancer patients’ LE only refer to the time of diagnosis as an estimate of the disease burden [3-9]. However, its relevance is not limited to the time of diagnosis but becomes even stronger for long-term survivors. Nonetheless, to the best of our knowledge, only one study has provided cancer survivors’ LE estimates not only by sex and age at diagnosis, but also by time since diagnosis and consequently by attained age after diagnosis . This detail is important because it allows to follow the patient over time and update his/her life expectancy conditioned to have survived up to that time and specific age. Life expectancy at a given age, for example at 70 years and after 10 years since diagnosis compared with that of healthy people of the same age and sex, is more sensible  information for patients than a probabilistic concept as conditional survival, often in the long term very close to 100%.
Several aspects of survivorship are modified by time since cancer diagnosis and life expectancy of patients, in particular quality of life . Current and future approaches to communication of life expectancies to patients should be based on solid evidence [3,4], presently scant.
The aim of this paper was to provide, for the first time in Italy, LE estimates for major cancer types by sex, age at diagnosis, and attained age after diagnosis, and to compare them with those from the age- and sex-matched general Italian population with the objective to better describe the changing impact of cancer on LE over time.
Materials and methods
This study used data collected by the network of population-based Italian cancer registries , which agreed to participate in the study and with at least 18 years of cancer registration as of December 31, 2011 (that is, Ferrara, Genova, Modena, Parma, Ragusa, Sassari, Varese, and Veneto, representing 10% of the entire Italian population in 2010) [8,12].
This study included all malignant tumours (International Classification of Diseases, Tenth Revision (ICD-10) C00-C43, C45-C96) and those with benign/uncertain behaviour or in situ bladder cancers. Non-melanoma skin cancers (ICD-10 C44) and cases identified only by their death certificates or autopsy findings were excluded. Only first diagnoses of cancers were retained. The third International Classification of Diseases for Oncology (ICD-O-3) was used to identify morphology subtypes.
Data from 722,737 Italian cancer patients were extracted in January 2017 from the AIRTUM database. Those included were diagnosed during the period 1985-2011 and followed-up for vital status until December 31, 2013.
In order to obtain stable estimates, all cancers-age-sex combinations that had no relative survival (RS) estimates or annual RS estimates up to 13 years of follow-up based on less than five cases were not considered in the analysis. Therefore, the selected cancers were stomach, colon, rectum, anus, lung, melanoma, bladder, thyroid, non-Hodgkin lymphoma, and leukaemias for both sexes; breast, cervix, corpus uteri, and ovary for females; and larynx, prostate, and testis for males. LE of the general population was provided by the National Institute of Statistics (ISTAT) based on age-specific survival probabilities observed in all birth cohorts born at any time and living during a single calendar period, 2010. LE of the general population was calculated using the standard period life table method . A period life table describes what would happen to a hypothetical cohort of persons if they experienced the age-specific mortality risks observed during the reference period. This assumption provides a useful representation of current mortality risks.