Long term prognosis of women with breast cancer in New Zealand: study of survival to 30 years.

The long term prognosis of women with breast cancer was studied by analysing retrospectively the 30 year survival of 2019 women with histologically proved breast cancer recorded at the National Cancer Registry in New Zealand between 1950 and 1954. Excess mortality rates for successive five year survival cohorts were calculated from the survival data. From the total cohort the excess mortality rate fell rapidly during the first 10 years and then became low after 20 years. There were no significant differences in excess mortality for the age cohorts. Most of the excess mortality for 20 years was due to deaths from breast cancer. In this study the prognosis for women with breast cancer approached normal after 20 years and the improvement in prognosis resulted from decreasing death rates from breast cancer.