Incidence and survival of primary metastatic breast cancer in Denmark; implication of breast cancer screening,...

Area of Science:

• Oncology
• Epidemiology
• Public Health

Background:

• Primary metastatic breast cancer (pMBC) represents 5-10% of breast cancer diagnoses with variable survival rates.
• Danish breast cancer incidence stabilized post-2010 after a prior increase.
• Factors like screening, staging, and classification significantly impact pMBC but are under-documented.

Purpose of the Study:

• To analyze trends in pMBC incidence, treatment, and survival in Denmark over two decades (2000-2020).
• To investigate changes in diagnostic practices and tumor subtype distribution.
• To assess the impact of these changes on patient outcomes.

Main Methods:

• Retrospective observational study of pMBC patients diagnosed between 2000 and 2020.
• Utilized data from the Danish Breast Cancer Group database and National Patient Register.
• Included diagnosis specifics, demographics, treatment, and follow-up data.

Main Results:

• 3,272 pMBC cases diagnosed; incidence rose significantly, especially in patients ≥70 years.
• Increased diagnosis of human epidermal growth factor receptor 2 (HER2)-positive cases; estrogen receptor (ER) status distribution remained stable.
• Diagnostic imaging (PET/CT or CT with bone evaluation) increased from 6% to 65%; overall survival improved from 23 to 33 months.
• Improved survival by year of diagnosis for ER-positive/HER2-positive disease; worse outcomes in the first 2 years for ER-negative/HER2-negative disease.

Conclusions:

• The study highlights evolving treatment and survival patterns for pMBC over 20 years.
• Changes in diagnostic staging, screening, and registration practices complicate definitive causal assessments.
• Further research is needed to establish clear relationships between interventions and improved survival outcomes.