breast cancer

Data and numbers

Introduction

Breast cancer begins in the cells of the lining (epithelium) of the ducts (85%) or lobules (15%) of the glandular tissue of the breasts. Initially, the cancerous tumor is confined to the duct or lobule (in situ), where it usually causes no symptoms and has minimal potential for spread (metastasis).

Over time, this cancer in situ (stage 0) can progress to invade surrounding breast tissue (invasive breast cancer), and then spread to nearby lymph nodes (regional metastasis) or to other organs in the body (distant metastasis) . When a woman dies of breast cancer, it is as a consequence of widespread metastasis.

Breast cancer treatment can be very effective, particularly when the disease is detected early. Treatment often consists of a combination of surgical removal, radiation therapy, and medication (hormonal therapy, chemotherapy, and/or targeted biologic therapy) to treat microscopic cancer that has spread from the breast tumor through the blood. Therefore, such treatment, which can prevent the progression and spread of cancer, saves lives.

scope of the problem

In 2020, 2.3 million women worldwide were diagnosed with breast cancer and 685,000 died from the disease. At the end of the same year, 7.8 million women who had been diagnosed with breast cancer in the previous five years were still alive, making this cancer the most prevalent in the world. Worldwide, disability-adjusted life years (DALYs) lost in women with breast cancer are estimated to exceed those due to any other cancer. Breast cancer affects women of any age after puberty in all countries of the world, but the rates increase in their adult life.

Between the 1930s and 1970s, breast cancer mortality showed little change. Improvements in survival began in the 1980s in countries that had early detection programs combined with different types of therapies to contain invasive disease.

Who is at risk?

Breast cancer is not a communicable or infectious disease. Unlike some cancers that have causes related to infectious processes, such as human papillomavirus (HPV) infection and cervical cancer, there are no known viral or bacterial infections related to the appearance of breast cancer.

About half of breast cancer cases are in women with no identifiable risk factors other than gender (female) and age (over 40 years). Some factors increase the risk of breast cancer, including aging, obesity, harmful use of alcohol, family history of breast cancer, history of radiation exposure, reproductive history (such as age at onset of menstrual periods and age at first pregnancy), tobacco use, and postmenopausal hormone therapy.

Behavioral choices and related interventions that reduce breast cancer risk include:

Unfortunately, even if all potentially modifiable risk factors could be controlled, the risk of breast cancer would only be reduced by no more than 30%.

Being female is the main risk factor for breast cancer. Approximately 0.5% to 1% of breast cancer cases affect men. Treatment of this disease in men follows the same principles as those applied to women.

A family history of breast cancer increases the risk of developing it, but most women who are diagnosed with breast cancer have no known family history of the disease. The lack of a known family history does not necessarily mean that a woman is less likely to develop breast cancer.

Some "highly penetrant" inherited gene mutations increase the risk of breast cancer, the most prevalent of which are mutations in the BRCA1, BRCA2, and PALB-2 genes. Women found to have mutations in these important genes may estimate the possibility of adopting risk reduction strategies such as surgical removal of both breasts. Consideration of such an invasive approach concerns only a very limited number of women, should be carefully weighed against all possible alternatives, and should not be adopted hastily.

Signs and symptoms

Breast cancer most often presents as a painless nodule or thickening in the breast. It is important that women who detect an abnormal swelling in the breast see a health professional without delaying more than 1-2 months even if they do not feel any pain associated with the nodule. Seeking medical attention at the first sign of a possible symptom contributes to greater treatment success.

Generally, the symptoms of breast cancer are as follows:

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There are a variety of reasons why breast lumps develop, most of which are not cancer. Up to 90% of breast masses are not cancerous. Noncancerous breast abnormalities include benign masses such as fibroadenomas and cysts, as well as infections.

Breast cancer can manifest itself in many different ways, so it is important to carry out a complete medical examination. Women with persistent abnormalities (usually lasting more than a month) should undergo some tests, such as imaging of the breast and in some cases taking tissue samples (biopsy) to determine if the mass is malignant (cancerous) or benign.

Advanced cancers can erode the skin and cause open sores (ulcerations) that are not necessarily painful. Women with non-healing wounds on the breasts should have a biopsy.

Breast cancer can spread to other parts of the body and cause other symptoms. Often, the most common first place where the spread can be detected is to the lymph nodes in the armpit, although it is possible to have cancerous lymph nodes that cannot be detected.

Over time, cancer cells can spread to other organs, such as the lungs, liver, brain, and bones. When they reach those organs, new cancer-related symptoms may appear, such as bone pain or headaches.

Treatment

Breast cancer treatment can be highly effective, with survival rates of 90% or higher, particularly when the disease is detected early. It usually consists of surgery and radiation therapy to slow the progression of the disease in the chest, lymph nodes, and surrounding areas (locoregional control), and systemic therapy (anticancer drugs given by mouth or intravenously) to treat and/or reduce the risk of cancer spread (metastasis). Anticancer drugs include endocrine (hormonal) therapy, chemotherapy, and in some cases targeted biological (antibody) therapy.

Previously, all cases of breast cancer were treated surgically with mastectomy (complete removal of the breast). When cancerous tumors are large, mastectomy is still necessary. Currently, most breast cancers can be treated with a minor procedure called a lumpectomy or partial mastectomy, in which only the tumor is removed. In those cases, radiation therapy is usually given to the breast to minimize the chances of cancer recurrence.

Lymph nodes are removed when surgery for invasive cancers is performed. In the past, complete removal of the axillary lymph node bed (complete axillary dissection) was considered necessary to prevent the spread of cancer. A minor procedure, called sentinel lymph node biopsy, is now preferred because it has fewer complications. In this intervention, dye and/or radioactive tracer is used to detect the first lymph nodes to which the cancer could spread from the breast.

Drug treatments or chemotherapy for breast cancer, which can be given before ("neoadjuvant") or after ("adjuvant") surgery, are based on biological subtyping of cancers. Cancers that express the estrogen receptor (ER) and/or the progesterone receptor (PR) are likely to respond to endocrine (hormonal) therapies such as tamoxifen or aromatase inhibitors. These drugs are given orally for 5 to 10 years, and reduce the chance of recurrence of "hormone receptor-positive" cancers by about half. Endocrine therapies can cause menopausal symptoms, but are generally well tolerated.

Cancerous tumors that do not express the ER or PR are "hormone receptor negative" and should be treated with chemotherapy unless they are very small. Currently available chemotherapy regimens are highly effective in reducing the chances of the cancer spreading or recurring and are usually given as outpatient treatment. In general, if there are no complications, chemotherapy for breast cancer does not require hospital admission.

Breast cancer can independently overexpress a molecule called the HER2/neu oncogene. This type of "HER2 positive" cancer lends itself to treatment with targeted biological agents such as trastuzumab. These agents are very effective but also very expensive, because they consist of antibodies and not chemicals. When targeted biological therapies are given, they are combined with chemotherapy to make them effective in killing cancer cells.

Radiation therapy also plays an important role in the treatment of breast cancer. In the early stages of breast cancer, radiation therapy can prevent a woman from having to have a mastectomy. In later stages of the disease, radiation therapy can reduce the risk of recurrence even when a mastectomy has been performed. In advanced stage breast cancer, in some circumstances radiation therapy can reduce the chance of dying from the disease.

The efficacy of breast cancer therapies depends on adherence to the full course of treatment. Partial treatment is less likely to lead to a positive result.

challenges

Breast cancer survival for at least five years after diagnosis ranges from over 90% in high-income countries to 66% and 40% in India and South Africa, respectively. In early countries, early detection and treatment have been successful, and should be implemented in resource-poor countries where some of the standardized tools are already in place. The vast majority of medicines used against cancer are already on the WHO Model List of Essential Medicines. Therefore, applying what we already know works can lead to significant improvements in breast cancer treatment worldwide. world.

global impact

Between the 1980s and 2020, age-standardized breast cancer mortality fell by 40% in high-income countries. Countries that have been successful in their efforts to reduce breast cancer mortality have achieved an annual reduction of 2% to 4%. If global annual mortality were reduced by 2.5%, between 2020 and 2040, 2.5 million deaths from breast cancer would be averted.

Strategies to improve breast cancer outcomes depend primarily on strengthening health systems to deliver treatments that are already known to be effective. These treatments are also important for managing other types of cancer and other non-neoplastic non-communicable diseases (NCDs). An excellent strategy, for example, is to have reliable referral pathways from primary health care facilities to district hospitals and specialist cancer centres.

The creation of these referral pathways is consistent with the approach required to manage cervical, lung, colorectal, and prostate cancers. To this end, breast cancer is a reference disease when creating itineraries for the management of other diseases.

WHO response

The goal of the WHO Global Initiative Against Breast Cancer is to reduce global mortality from this disease by 2.5% per year, thereby avoiding 2.5 million deaths worldwide between 2020 and 2040. . If that goal is met, by 2030 25% of breast cancer deaths among women under 70 years of age would be prevented, and by 2040 that figure would be 40%. The three pillars to achieve this goal are: health promotion for early detection; timely diagnosis; and comprehensive management of breast cancer.

If public health education is provided to women to improve their knowledge of the signs and symptoms of breast cancer and so that they, together with their families, understand the importance of early detection and treatment, more women would attend health professionals when they first suspect they have breast cancer and before any cancer already present has progressed. This is possible even when mammographic screening equipment is not available, which is currently unfeasible in many countries.

Public health education should be combined with education of health workers about the signs and symptoms of early breast cancer so that, where appropriate, women are referred for diagnostic services.

Rapid diagnosis must go hand in hand with effective cancer treatment, which in many health facilities requires a certain degree of specialized care for the disease. By establishing centralized services in a dedicated cancer center or hospital, using breast cancer as a model, treatment for breast cancer can be optimized while improving treatment for other cancers.

[1] Age normalization is a technique used to be able to compare populations when the age profiles of those populations are considerably different.

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