Multiple births and breast cancer prognosis: a population based study

Area of Science:

• Reproductive Health
• Oncology
• Epidemiology

Background:

• Limited research exists on reproductive factors influencing breast cancer survival.
• Most studies focus on breast cancer risk rather than survival outcomes.
• The impact of birth type (singleton vs. multiple) on breast cancer survival is understudied.

Purpose of the Study:

• To analyze the effect of multiple births versus single births on breast cancer survival.
• To investigate the association between birth type and breast cancer-specific fatality.
• To identify prognostic factors for breast cancer patients with a history of childbirth.

Main Methods:

• Population-based cohort study of 30,619 women diagnosed with primary breast cancer (1958-1998) in Sweden.
• Linking Swedish registries: Swedish Cancer Registry, Cause of Death Registry, Swedish Generation Registry, and Population registries.
• Cox proportional hazards model used to quantify the association between singleton/multiple births and breast cancer fatality.

Main Results:

• Breast cancer diagnosed within 5 years of childbirth (singleton or multiple) was associated with increased fatality.
• This survival disadvantage diminished by 5 years post-childbirth.
• A protective effect on survival was observed beyond 5 years after childbirth.

Conclusions:

• Childbirth is generally associated with decreased breast cancer risk.
• Breast cancer diagnosed within 5 years of childbirth presents a survival disadvantage.
• Multiple births preceding diagnosis within 5 years are a negative prognostic factor, requiring consideration in patient counseling and treatment.