National estimates of cancer patients survival in Italy: a model-based method.

AIMS AND BACKGROUND: To provide model-based estimates of all cancers patient survival in Italy and in Italian large geographical areas (North-West, North-East, Center, South), where only partial coverage of cancer registries data is available, and to describe them in terms of time trends. Moreover, to measure the degree of representativeness of cancer patient survival obtained from Italian cancer registries data. METHODS: Relative survival in the four main Italian geographical areas was estimated by a parametric mixture model belonging to the class of "cure" survival models. Data used are from Italian cancer registries, stratified by sex, period of diagnosis and age. The Italian national survival was obtained as a weighted average of these area-specific estimates, with weights proportional to the number of estimated incident cases in every area. The model takes into account also differences in survival temporal trends between the areas. RESULTS: Relative survival for all cancers combined in Italian patients diagnosed in 1990-1994 was estimated to be higher in women (53%) than in men (38%) at 5 years from the diagnosis. The survival trend is increasing by period and decreasing by age, both for men and women. The greatest gain in terms of survival was obtained by the elderly, with annual mean growth rates in the period 1978-1994 equal to 3.5% and 3.2% for men and women, respectively. More than 50% of the youngest cancer patients were "cured", whereas for the elderly this proportion dropped to 15% and 25% for men and women, respectively. The South of Italy had the lowest survival and the North the most pronounced increase. CONCLUSIONS: The obtained national survival estimates are similar, but not identical, to previously published estimates, in which Italian registries' data were pooled without any adjustment for geographical representativeness. The four Italian areas have different survival levels and trends, showing variability within the country. The differences in survival between men and women may be explained by the different proportion of lethal cancers. Among males, most cases had a poor prognosis (lung and stomach cancers), whereas among females the largest proportion was made up of curable and less lethal cancers (breast cancer).