Changing patterns in breast cancer incidence trends.

Area of Science:

• Epidemiology
• Biostatistics
• Public Health

Background:

• Breast cancer incidence rates in U.S. women have shown a persistent increase over decades.
• The underlying causes for these escalating trends remain incompletely understood.
• A recent acceleration in incidence suggests a potential link to enhanced population screening efforts.

Purpose of the Study:

• To apply a novel age-period-cohort framework to dissect temporal components influencing breast cancer incidence trends.
• To evaluate the specific contributions of age, diagnosis year (period), and birth year (cohort) to observed incidence patterns.
• To quantify the impact of increased screening, particularly after 1982, on breast cancer incidence rates.

Main Methods:

• Utilized breast cancer incidence data (ICD-O 174.0-174.9) from the Surveillance, Epidemiology and End Results (SEER) registries.
• Employed a unique approach within the age-period-cohort framework, using single-year intervals for age and diagnosis year.
• Fitted a log-linear age-period-cohort model using Poisson regression to estimate separate time trends for each component.

Main Results:

• Period trends showed a significant increase after 1982, coinciding with the implementation of more aggressive screening protocols.
• This upturn in period trends was more pronounced in women over 40 years of age.
• Cohort trends demonstrated a steady increase, with recent cohorts showing a plateau for women aged 50 and younger, while older cohorts continued to rise.

Conclusions:

• The study provides evidence that increased screening, particularly post-1982, is a significant contributor to the observed upturn in breast cancer incidence.
• The age-period-cohort model effectively disentangles the effects of aging, calendar time, and birth cohort on incidence rates.
• Estimates suggest a notable magnitude of incidence increase attributable to the intensified screening efforts.