LONG-TERM SURVIVAL OF BREAST-CANCER IN NORWAY BY AGE AND CLINICAL STAGE

In this paper 25-year survival for 8802 Nonwegian women with breast ca ncer diagnosed during the period 1965 to 1974 is studied. It is sugges ted that some of the contradictory reports in the literature of the pr ognostic effect of age and clinical stage on long-term survival may be caused by interactions and time varying effects of covariates. When u sing a linear non-parametric regression model that allows the covariat es to vary over time, age and clinical stage are found to be significa nt long-term prognostic factors. A significantly higher excess mortali ty for women less than 35 years at diagnosis disappeared after 8 years , while for those above 55 years an important effect of age on the lon g-term survival, especially for those with regional cancer, was seen. The effect of clinical stage on survival varies strongly over time, an d was significant between 15 and 20 years. (C) 1997 by John Wiley & So ns, Ltd.