Mortality after contralateral breast cancer in Denmark.

Area of Science:

• Oncology
• Epidemiology
• Cancer Research

Background:

• Understanding survival outcomes after a contralateral breast cancer (CBC) diagnosis is crucial.
• Prognostic factors for CBC, especially concerning survival, require further elucidation.

Purpose of the Study:

• To investigate survival patterns following a CBC diagnosis.
• To analyze the impact of the time interval between first and second breast cancer diagnoses on survival.
• To determine the role of age at CBC diagnosis in survival outcomes.

Main Methods:

• Utilized nationwide Danish Breast Cancer Cooperative Group data (1978-2012) with 68,466 initial breast cancer patients.
• Identified 3,004 patients who developed CBC and followed them for breast cancer-specific death until 2015.
• Employed Cox proportional hazard regression and Aalen-Johansen methods to estimate mortality risks and cumulative mortality.

Main Results:

• Patients diagnosed with CBC had more than double the rate of dying from breast cancer compared to unilateral breast cancer (UBC) patients (HR 2.48).
• A short interval (<5 years) between diagnoses was linked to higher mortality after CBC in patients younger than 70 at CBC diagnosis.
• This association between short interval and mortality was not observed in patients aged 70 or older at CBC diagnosis.

Conclusions:

• Breast cancer-specific mortality is significantly higher following a CBC diagnosis compared to before.
• A short time interval between breast cancer diagnoses is a critical risk factor for mortality in patients diagnosed with CBC before age 70.