Population-based breast cancer survival. Mammographic screening activities in central Italy.

BACKGROUND

The aim of this study was to evaluate the effect on 5-year survival of patients with invasive breast cancer relative to demographic and clinical variables (age, residence, and disease diffusion) and to early diagnostic procedures performed in the area.

METHODS

The observed (Kaplan-Meier method) and relative 5-year survival in 1263 patients with invasive breast cancer in the Province of Florence, Italy, between 1985-1986 (source: Tuscany Cancer Registry) are presented. The results were compared with those of other European areas and of the Surveillance, Epidemiology, and End Results Program. The Cox model is used to evaluate the effects of age at diagnosis (5-year age groups), disease diffusion (localized, regional, distant, unspecified), residence (Municipality of Florence, screening area, other municipalities), and source of diagnosis (Center for the Study and Prevention of Cancer, hospitals) on observed survival.

RESULTS

Observed 5-year survival was 68.4% (Kaplan-Meier method) and relative 5-year survival was 75.4%. Relative survival for patients younger than age 35 at diagnosis was high (82.3%); it decreased slowly from 80.5% in the group of patients 35-44 years of age, to 74.0% in those 65-74 years of age, and steeply decreased to 68.1% in those 75 years of age and older. Relative 5-year survival in Florence was lower only than that observed in Switzerland (Geneva) and in the USA (whites). Five-year prognosis was worse in women 70 years of age or older, in advanced stages, in residents of municipalities not involved in the screening program, and in cases diagnosed in hospitals. The gain in survival may be explained partially by lead-time effect and by length bias due to early diagnosis both in self-referred women and in screening-detected cases. In these cases, though, the better prognosis, although attenuated, persisted after adjustment by disease diffusion.

CONCLUSIONS

The results suggest that the early diagnosis of breast cancer in self-referred women affects prognosis, at least concerning 5-year survival. Moreover, although lead-time effect and length bias cannot be excluded in this study, screening by personal invitation may reduce the disadvantage in the survival of patients with breast cancer often observed in rural areas.