The select of prognosis factors for using a polyfactorial analysis of the treatment results in 496 women with breast cancer of st. I after 5 years of monitoring identifi ed that the tumor increased in 15,5% cases. The following factors contributed to an increase in the tumor size: placement of the tumor in the central sector (53,6%), multi-centric affection (46,4%), use only of the surgical treatment (22,2%), the diameter of the tumor exceeding 1,0 cm (19,6%), hyperdosed radiotherapy as the fi rst stage of treatment (16,4%). The best results, i.e. the lowest rate of progression, were obtained with the patients with the diameter of the tumor under or equal with 0,5 cm (2,3%) and in cases when chemotherapy was the fi rst stage of treatment (10,0%).