RISKS AND PROBABILITIES OF BREAST-CANCER - SHORT-TERM VERSUS LIFETIMEPROBABILITIES

Objective: To calculate age-specific short-term and lifetime probabili ties of breast cancer among a cohort of Canadian women. Design: Double decrement life table. Setting: Alberta. Subjects: Women with first in vasive breast cancers registered with the Alberta Cancer Registry betw een 1985 and 1987. Main outcome measures: Lifetime probability of brea st cancer from birth and for women at various ages; short-term (up to 10 years) probability of breast cancer for women at various ages. Resu lts: The lifetime probability of breast Cancer is 10.17% at birth and peaks at 10.34% at age 25 years, after which it decreases owing to a d ecline in the number of years over which breast cancer risk will be ex perienced. However, the probability of manifesting breast cancer in th e next year increases steadily from the age of 30 onward, reaching 0.3 6% at 85 years. The probability of manifesting the disease within the next 10 years peaks at 2.97% at age 70 and decreases thereafter, again owing to declining probabilities of surviving the interval. Conclusio ns: Given that the incidence of breast cancer among Albertan women dur ing the study period was similar to the national average, we conclude that currently more than 1 in 10 women in Canada can expect to have br east cancer at some point during their life. However, risk varies cons iderably over a woman's lifetime, with most risk concentrated after ag e 49. On the basis of the shorter-term age-specific risks that we pres ent, the clinician can put breast cancer risk into