Survival of breast cancer patients in Lithuania and Norway, 1988-1992.

In Norway, the incidence of breast cancer is almost twice that in Lithuania, whereas the mortality rates of the disease are approximately the same in both countries. The aim of the present study was to compare the survival of breast cancer patients in the two countries according to stage. The material from both countries included cases diagnosed between 1988 and 1992 with complete follow-up of date of death to the end of 1995. The Norwegian data consisted of all 9403 new cases recorded by the Norwegian Cancer Registry. The Lithuanian data included in all 1649 new cases treated at the Oncology Centre in Vilnius, which represents 40% of breast cancer cases in Lithuania--these cases had the same distribution of the disease by age and stage as for the whole country. The overall 5-year relative survival was lower in Lithuania (57.3%) than in Norway (78.4%). Lower survival was observed in Lithuania compared with Norway for all stages. In stage I, the difference was 7.8% in absolute terms which could be explained by a higher proportion of small tumours among the Norwegian cancer cases (63.7% of tumours were 2 cm or less, while in Lithuania the proportion of small stage I tumours was only 27.9%). Therefore, early diagnosis within the stage I category seems relevant. The difference in survival was, however, most pronounced in stage II (20%) and III (29%). In Norway, the better overall survival is partly explained by a more favourable stage distribution. The lower survival of Lithuanian cases within stage categories could be explained by more advanced metastases to regional lymph nodes and by higher proportions of large tumours within stage.