Breast cancer

What you need to know

Breast cancer accounts for approximately 25-30% of all cancers in women worldwide. It is estimated that 1 in 8 women in Spain will be diagnosed with breast cancer during their lifetime.

It is a disease that originates when breast cells begin to grow abnormally and uncontrollably until they form a tumor, which can sometimes be felt as a lump, although other times it is only detected by mammography or ultrasound.

Important message: Although these figures may seem alarming, it is essential to remember that early diagnosis and advances in treatment have significantly improved the prognosis. Today, most women diagnosed with breast cancer can lead normal lives.

Where does breast cancer originate?

The breast is made up of ducts (which transport milk) and lobules (which produce it). Cancer cells can begin to grow in any of these structures:

Types by location:

• Ductal carcinoma (80% of cases): Originates in the ducts. It generally forms more visible masses and is easier to detect.
• Lobular carcinoma (20% of cases): Originates in the lobules. The cells grow singly or in rows; it is more diffuse and sometimes more difficult to visualize on imaging tests.

Degree of invasion:

• Carcinoma in situ: Abnormal cells confined within their original structure, without yet invasive capacity.
• Invasive carcinoma: The cells have crossed the basement membrane and can affect nearby tissues, lymph nodes, or spread through the bloodstream.

Molecular subtypes of breast cancer:

Not all breast cancers are the same. Thanks to advances in medicine, we now know that there are different molecular subtypes, and this classification is essential for choosing the most appropriate treatment for each case.

This classification is obtained through analysis of tumor tissue (biopsy), evaluating specific markers:

1. Luminal A
   • Characteristics: Positive hormone receptors (estrogen and/or progesterone), HER2 negative
   • Behavior: Slower growth
   • Prognosis: Better overall prognosis
   • Treatment: Respond well to hormonal therapies
2. Luminal B
   • Characteristics: Positive hormone receptors, may be HER2 positive or have increased cell proliferation
   • Behavior: Somewhat more aggressive than Luminal A
   • Treatment: May require chemotherapy in addition to hormonal therapy
3. HER2 positive (non-luminal)
   • Characteristics: They do not have hormone receptors, but express a lot of HER2 protein
   • Behavior: More aggressive
   • Prognosis: Has improved significantly thanks to therapies targeting HER2
   • Treatment: Specific anti-HER2 therapies (trastuzumab, pertuzumab, etc.)
4. Triple negative
   • Characteristics: They do not have hormone receptors or HER2
   • Behavior: May grow faster, more common in younger women
   • Treatment: Chemotherapy is very effective, new targeted therapies in development

Genetic tumor testing: When is it useful?

In addition to basic molecular classification, in some cases, more in-depth genetic studies of the tumor can be performed to further personalize treatment:

When are they used? Your medical team will assess whether you need any of these tests based on the specific characteristics of your tumor and your clinical situation.

Breast Cancer Treatment

Treatment is never the same for every patient. It is designed in a completely personalized way, considering:

• Molecular type and subtype of cancer
• Tumor size
• Lymph node involvement
• General health status
• Patient age and preferences

Who decides on treatment?

Decisions are made by a Multidisciplinary Breast Committee, composed of:

• Medical oncologists
• Radiation oncologists
• Specialized surgeons
• Pathologists
• Radiologists
• Gynecologists (when applicable)
• Specialized nurses

This team reviews each case individually to propose the best treatment.

Treatment options

1. Surgery
   • Conservative surgery: Only the tumor and a margin of healthy tissue are removed
   • Mastectomy: Complete removal of the breast
   • Lymph node surgery: Evaluation of axillary nodes (sentinel lymph node dissection or axillary lymph node dissection)
2. Radiation therapy:
   • Uses radiation to eliminate residual tumor cells
   • It is usually indicated after conservative surgery
   • In some cases, also after mastectomy
3. Systemic treatment
   • Chemotherapy: Can be neoadjuvant (before surgery) or adjuvant (afterward)
   • Hormonal therapy: For tumors with hormone receptors
   • Targeted therapies: Such as anti-HER2 for HER2-positive tumors
   • Immunotherapy: In development for certain subtypes

Treatment Sequence

The order varies depending on the case:

• Large tumors or those with affected lymph nodes: May begin with chemotherapy to reduce the size.
• Small tumors: May undergo surgery first and consider additional treatments later.
• Important: Not all patients need all treatments.

Risk Factors and Prevention

Non-modifiable risk factors:

• Age (increases with age)
• Female sex
• Family history
• Genetic mutations (BRCA1, BRCA2, etc.)
• Reproductive history (early menarche, late menopause)

Modifiable factors:

• Sedentary lifestyle
• Overweight and obesity
• Alcohol consumption
• Long-term hormone replacement therapy

Prevention:

• Regular screening: Mammograms based on age and risk factors
• Healthy lifestyle: Regular exercise, balanced diet, healthy weight
• Self-examination: Check your breasts for changes
• Genetic counseling: If there is a significant family history

Symptoms that require consultation

Consult a doctor if you notice:

• A lump or mass in the breast or armpit
• Changes in the size or shape of the breast
• Skin changes (dimpling, redness)
• Nipple changes (retraction, discharge)
• Persistent breast pain

Remember: Most breast lumps are not cancer, but they should always be evaluated by a professional.

Current prognosis

Encouraging data:

• 5-year survival rate exceeds 85% in most developed countries
• Early diagnosis significantly increases the chances of cure
• Personalized treatments have improved both survival and quality of life

Final Message

Breast cancer is not a single disease, but rather a group of distinct conditions that require personalized approaches. Thanks to research and medical advances, we can now offer increasingly precise and effective treatments.

If you have received this diagnosis:

• You are not alone: you have a specialized multidisciplinary team.
• Treatment will be tailored specifically to your case.
• Current advances offer very encouraging prospects.
• Your voice and preferences are important in therapeutic decisions.

Helpful resources for patients

Spain:

• Sociedad Española de Oncología Médica (SEOM)
• Asociación Española Contra el Cáncer (AECC)
• Fundación Grupo Español de Investigación en Cáncer de Mama (GEICAM)

International resources

• American Cancer Society - Breast Cancer Information
• National Cancer Institute

Useful applications:

• AECC - App oficial con información y recursos
• CancerNet Mobile - De la American Society of Clinical Oncology

Bibliography:

Sung, H., Ferlay, J., Siegel, R.L. et al. Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA Cancer J Clin. 2021;71(3):209-249.

Perou, C.M., Sørlie, T., Eisen, M.B. et al. Molecular portraits of human breast tumours. Nature 2000;406:747–752.

Gándara-Cortes M, Vázquez-Boquete Á, et al. Breast cancer subtype discrimination using standardized 4-IHC and digital image analysis. Virchows Arch. 2018;472(2):195-203.

Cardoso, F., van't Veer, L.J., Bogaerts, J. et al. 70-Gene Signature as an Aid to Treatment Decisions in Early-Stage Breast Cancer. N Engl J Med 2016;375:717-729.

Sparano, J.A., Gray, R.J., Makower, D.F. et al. Prospective Validation of a 21-Gene Expression Assay in Breast Cancer. N Engl J Med 2015;373:2005-2014.