Favourable outcome of screen-detected breast cancers

The increased incidence and reduced mortality for breast cancer reflect the success of the screening programs. The results of our screening program, published on BMC Cancer, confirm a favourable outcome of screen-detected breast cancers in terms of five-year overall and event-free survival. At the aim to evaluate the early efficacy of this screening, we reviewed all breast cancers detected between October 1995 and December 2000 in the province of Modena, in women 50-69 aged, exposed to screening and in women  diagnosed over the same time-interval out of screening.

587 new breast cancers were detected by the screening program, while 471 were diagnosed outside the program. The screen-detected breast cancers were smaller, more likely node negative, with low histological grade, low proliferative activity and positive receptors status.

With a median follow-up of 52 months, the majority of deaths occurred in patients with breast cancer non- screen-detected (p<0.0001). We observed a 9.6% of events in the screen-detected group and a 22.6% in the non-screen-detected group (p <0.0001). A significant difference was also observed in the number of disease recurrences (33 in the screen-detected group and 42 in the non-screen-detected group, p=0.02) and of second breast cancers (1 vs 9, p=0.02). The 5-year event-free survival  was equal to 89% and 75% among the women participants and non-participants to the screening, respectively (p=0.0001).  The 5-year overall survival was 94% in the screen-detected group and 84% in the non screen-detected group (p=0.0001), also after adjustment for calculated lead-time and length biases. A significant difference was seen also for negative and positive nodes patients between the two groups.

Our data clearly show that the major cause for the decreasing breast cancer mortality is the smaller tumour size, associated with the earlier detection by the screening. Finally, a cancer registry should be implemented in every area covered by screening programs.

Bibliographical reference:

Cortesi L et al.: "Prognosis of screen-detected breast cancers: results of a population based study", BMC Cancer. 2006 Jan 23;6(1):17

Laura Cortesi

Dipartimento di Oncologia ed Ematologia, Università di Modena e Reggio Emilia, Italy