Breast cancer

What is this ?

Breast cancer is the most common cancer in women, accounting for over a third of all new cancer cases (61,214 new cases in 2023), representing a third of female cancers (source: INCA).

Breast cancers remain the leading cause of cancer mortality in women.

Over the past few years, this mortality rate has been decreasing despite an increase in incidence: mortality has decreased by 1.6% per year between 2010 and 2018. This decrease is mainly due to screening, which allows for the early detection of cancers: currently, 60% of breast cancers are diagnosed at the localized stage. It is also due to advancements in the treatments for these cancers, which are progressing more rapidly.

This cancer most often develops after the age of 60. Indeed, the risk increases with age, although it can affect very young women, with 20% of breast cancers occurring before the age of 50.

Approximately 5% of breast cancers occur in a familial genetic context (such as BRCA or PALB2 genetic mutations, for example).

Some statistics on breast cancer

There are national screening programs. The one implemented in France targets women aged 50 to 74, offering them a mammogram every two years. Given the still too low participation rate, 4 out of 10 cancers are still diagnosed at an intermediate or advanced stage.

Survival rates for breast cancer patients have improved partly due to advances in screening. Early detection and advances in treatments have also contributed to this improvement. Additionally, the survival rate for localized breast cancer is currently estimated at 88% at 5 years.

Breast cancer can also affect men, although this is very rare (less than 1%). The incidence of this cancer has been increasing over the past 20 years, though mortality rates are decreasing.

Breast cancers types

Three types of cancer are classified based on the presence of certain receptors (sensors) on the surface of cancer cells (hormone receptors and the HER2 receptor).

• Hormone-sensitive breast cancers, also known as luminal cancers, have hormone receptors on their surface, making them sensitive to hormone therapy. They represent approximately 75% of breast cancers.
• HER2-positive breast cancers have a strong overexpression of the HER2 receptor on their surface, making them sensitive to anti-HER2 treatment. They account for between 10 and 15% of breast cancers.
• Triple-negative breast cancers do not have hormone receptors or HER2 on the surface of the cells. Chemotherapy is often recommended for this type of cancer due to its aggressiveness.

There are also ductal carcinomas in situ, which are cancerous cells that do not invade the breast tissue and do not pose a risk of metastasis. However, they must be treated as they can progress to invasive cancer.

Interview with Professor Mahasti Saghatchian

Causes and risk factors

Risk factors for breast cancer can be genetic, hormonal, or related to lifestyle, although this does not fully explain the occurrence of breast cancer in a particular woman.

Breast cancer risk factors include:

• Age
• Family history of breast cancer, possibly with genetic predisposition
• Previous breast cancer or precancerous lesions
• Overweight or obesity (after menopause)
• Alcohol consumption
• Hormonal treatments, especially taken over a prolonged period (hormonal contraception or hormone replacement therapy)
• History of radiation therapy to the chest wall

Screening

Screening is performed using a mammographic examination, sometimes supplemented with an ultrasound if the breasts are dense.

Its benefits are demonstrated from the age of 40, although the starting age and frequency of mammograms may be adjusted based on risk factors or individual risk assessment tools.

For patients at very high risk due to familial mutation, breast MRI is also recommended.

Symptoms

Thanks to screening, cancer can be diagnosed before the appearance of symptoms.

However, it can also manifest as a palpable mass in the breast, even though these masses are most often non-cancerous.

Symptoms associated with breast cancer may include:

• Thickening of the skin of the breast, sometimes localized to a specific area
• Change in breast size or shape
• Nipple discharge, sometimes bloody
• A lump or swelling in the armpit
• Skin or nipple retraction
• Redness of the skin of the breast or nipple
• Changes in the appearance of the nipple, nipple eczema

Diagnosis of breast cancer

The diagnosis of breast cancer requires imaging examinations:

• Mammography and breast ultrasound with axillary ultrasound
• Micro or macro biopsy (needle biopsy) of the anomaly detected during clinical examination or imaging
• In some cases, complemented by breast MRI.

The biopsy, performed to obtain tissue samples, is analyzed in the laboratory (this is anatomopathology) and is necessary to confirm the cancer diagnosis and determine its type.

For a comprehensive diagnosis, depending on the size and type of cancer, additional staging may be necessary:

• Thoraco-abdomino-pelvic CT scan and bone scintigraphy
• PET-Scan
• Comprehensive blood tests including CA 15.3 marker levels

Treatments

When breast cancer is diagnosed at a localized stage, the treatment aims to cure the disease while also reducing the risk of recurrence and spread to other organs.

A combination of several types of treatments is typically used: surgery, chemotherapy, radiotherapy, hormone therapy, and anti-HER2 targeted therapies.

Each treatment modality is tailored to each patient based on the type and extent of their breast cancer.

Sometimes, it may be necessary to perform a mastectomy (removal of the breast), but in such cases, reconstruction techniques can be performed immediately or delayed.

If the cancer has spread to other organs (metastasis), the treatment primarily involves medication such as chemotherapy, hormone therapy, or targeted therapies. Radiation therapy or surgery for metastases may be considered in certain cases.

The goal of treatment is to prevent the progression of the disease, prolong survival, and manage symptoms associated with cancer.

Immunotherapy is now also used as a neoadjuvant and adjuvant treatment for triple-negative breast cancer. Immunotherapy stimulates the immune system to eliminate tumor cells.