Breast cancer

Breast cancer

Breast cancer is the most common female malignancy and accounts for approximately 30% of all new cancer cases among women. Women have a one in nine lifetime-risk of developing breast cancer (1,2).

Epidemiology

• incidence:
  • increases with age, doubling every 10 years until menopause, after which the rate of increase slows down
  • most common cancer in the UK
    • approximately 54,000 new cases of invasive disease diagnosed annually
    • around 7,000 new cases of pre-invasive (in situ) disease diagnosed annually
  • gender distribution:
    • predominantly occurs in women
    • just over 300 men in the UK are diagnosed with invasive breast cancer every year
• prognosis and survival:
  • most breast cancers are diagnosed at an early stage and are therefore potentially curable with modern treatments
  • survival rates have improved over recent decades:
    • almost 90% of women survive > 5 years after diagnosis
  • survival is highly stage-dependent:
    • only 15% of women diagnosed with stage IV disease are alive at 5 years
  • mortality burden:
    • leading cause of death in women aged 35-49 years
    • second only to lung cancer as the leading cause of cancer death in all women

Metastatic breast cancer

Metastatic breast cancer is an advanced stage of the disease when it has spread to distant organs.

• presentation:
  • an estimated 5% of patients present with de novo metastatic breast cancer
  • approximately 30% of people who present with localised breast cancer will later develop metastatic disease
• common sites of metastasis:
  • bone, liver, lung, and brain
• NICE staging constraints (3):
  • invasive lobular carcinoma variant caveat: * standard FDG PET-CT has a significantly lower diagnostic accuracy for lobular variants compared to ductal variants
  • equivocal staging pathway:
    • alternating imaging pathways (e.g., sequentially using contrast-enhanced CT and PET-CT) are required if initial staging is uncertain

Risk factors (4)

• gender: main risk factor is being female; the disease is 100 times less common in men
• age: a disease of ageing, with risk increasing with increasing age
• lifestyle factors:
  • increased risk: obesity, alcohol intake, and use of hormone replacement therapy (HRT)
  • protective factors: physical activity and breastfeeding
• genetics: about 5% of breast cancers are due to inherited mutations in high-risk genes (e.g., BRCA1, BRCA2, and p53)

Clinical evidence

• Taylor et al. (5):
  • population-based observational cohort study found that since the 1990s, the 5-year risk of death from breast cancer has decreased from 14.4% to 4.9% overall
  • reductions were observed across nearly all patient groups
• EBCTCG trials pooled analysis (6):
  • women diagnosed since 2000 have about a 20% lower rate of distant recurrence compared to those diagnosed in the 1990s
  • major drivers of improvement include a greater proportion of women with lower-risk disease entering trials and improved adjuvant systemic treatments

References

1. Siegel RL, Giaquinto AN, Jemal A. Cancer statistics, 2024. CA Cancer J Clin. 2024 Jan-Feb;74(1):12-49.
2. Breast cancer statistics. Cancer Research UK. 2024 online publication.
3. NICE (July 2026). Advanced breast cancer: diagnosis and treatment (Clinical Guideline CG81).
4. NICE (February 2025). Early and locally advanced breast cancer: diagnosis and management (NICE Guideline NG101).
5. Taylor C, McGale P, Probert J, et al. Breast cancer mortality in 500,000 women with early invasive breast cancer in England, 1993-2015: population based observational cohort study. BMJ 2023; 381:e074684.
6. Early Breast Cancer Trialists' Collaborative Group. Reductions in recurrence in women with early breast cancer entering clinical trials between 1990 and 2009: a pooled analysis of 155,746 women in 151 trials. Lancet October 12th 2024.