Breast cancer
Breast cancer is cancer of breast tissue. Worldwide, it is the most common form of cancer in females, affecting approximately one out of twelve to thirteen women who reach age ninety at some stage of their life in the Western world. It is (after lung cancer) the second most fatal cancer in women.History of breast cancer
(back to top)Breast cancer is one of the oldest known forms of cancer tumors. Our oldest description of cancer (although the term cancer was not used) was discovered in Egypt and dates back to approximately 1600 B.C. The Edwin Smith Papyrus, or writing, describes 8 cases of tumors or ulcers of the breast that were treated by cauterization, with a tool called "the fire drill." The writing says about the disease, "There is no treatment."
Types of breast cancer
(back to top)- DCIS: Ductal Carcinoma in Situ
- LCIS: Lobal Carcinoma in Situ
- Invasive ductal carcinoma
- Invasive lobal carcinoma
- Inflamatory breast cancer
- Paget's disease
Epidemiologic risk factors and etiology
(back to top)It is important to have a model of causation of a disease in order to distinguish epidemiological risk factors or associations with disease, from the biological etiology and primary cause, secondary co-factors, and simple promoters of the disease, given the underlying primary cause.The first work on breast cancer epidemiology was done by Janet Lane-Claypon, who published a comparative study in 1926 of 500 breast cancer cases and 500 control patients of the same background and lifestyle for the British Ministry of Health.
Today, breast cancer, like other forms of cancer, is considered to be a result of damage to DNA. How this mechanism may occur comes from several known or hypothesized factors (such as exposure to ionizing radiation). Some factors lead to an increased rate of mutation (exposure to estrogens) and decreased repair (the BRCA1, BRCA2 and p53 genes). Although many epidemiological risk factors, and biological co-factors and promoters have been identified, the majority of breast cancer incidence remains unattributable, and the primary cause is unknown.
Dietary influences have been proposed and examined, but these are small effects, and do not distinguish differences in risk within populations, as well as they do between populations.
A significant environmental effect was revealed by the large difference in breast cancer incidence between countries and continents, and a migration effect which slowly increases the risk of breast cancer even across generations after migration from a country of lower incidence to a country of higher incidence, such as moving from China or Japan to the United States.
Humans are not the only mammal prone to breast cancer. Some strains of mice, namely the house mouse (Mus domesticus) are prone to breast cancer which is caused by infection with the mouse mammary tumour virus (MMTV or "Bittner virus" for its discoverer Hans Bittner), by random insertional mutagenesis. Suspicion of MMTV or other viruses in human breast cancer is controversial, and the idea is not generally accepted for lack of direct and definitive evidence. There is much more research in diagnosis and treatment of breast cancer than in its cause.
Age
(back to top)The probability of breast cancer rises with age but breast cancer tends to be more aggressive when it occurs in younger women. One type of breast cancer that is especially aggressive and disproportionately occurs in younger women is inflammatory breast cancer. It is initially staged as Stage IIIb or Stage IV. It also is unique because it often does not present with a lump so that it often is not detected by mammography or ultrasound. It presents with the signs and symptoms of a breast infection like mastitis.
Genes
(back to top)Alcohol
(back to top)The National Institute on Alcohol Abuse and Alcoholism (NIAAA) concludes that "Chronic alcohol consumption has been associated with a small (averaging 10 percent) increase in a woman's risk of breast cancer (Friedenreich et al.; Longnecker; Nasca). According to these studies, the risk appears to increase as the quantity and duration of alcohol consumption increases. Other studies, however, have found no evidence of such a link (Chu et al. ; Schatzkin et al.; Webser et al)."
The Committee on Carcinogenicity of Chemicals in Food, Consumer Products
It has been reported that "Two drinks daily increase the risk of getting breast cancer by about 25 percent." (NCI) but the evidence is inconsistent. The Framingham study has carefully tracked individuals since the 1940s. Data from that research found that drinking alcohol moderately did not increase breast cancer risk (Wellness Facts). Similarly, research by the Danish National Institute for Public Health found that moderate drinking had virtually no effect on breast cancer risk (Petri et al.).
Breast cancer constitutes about 7.3% of all cancers
"Folate intake counteracts breast cancer risk associated with alcohol consumption" Mayo Clinic news release June 26 2001
Light levels
(back to top)Researchers at the National Cancer Institute and National Institute of Environmental Health Sciences have concluded a study that suggests that artificial light can be a cause of breast cancer. The Independent
Hormones
(back to top)The risk decreases to that of those who have never used such combined therapy ten years after cessation of use. The scientists described combined oral estrogen-progesterone contraceptives as "carcinogenic to humans."
Other
(back to top)Unproven
(back to top)- It has been hypothesized that abortion may increase the risk of breast cancer because of hormones in early pregnancy. Recent large studies do not support this association. American Cancer Society. (2006-10-03).
- Although not well quantified there has long been a concern about risk associated with environmental estrogenic compounds, such as dioxins, or phytoestrogens such as found in soy beans. Gikas PD, Mokbel K. (2005)
- Aluminum salts such as those used in anti-perspirants have recently been classified as metalloestrogens. In research published in the Journal of Applied Toxicology, Dr. Philippa D. Darby of the University of Reading has shown that aluminum salts increase estrogen-related gene expression in human breast cancer cells grown in the laboratory. Harding, Anne. (2006)
Symptoms
(back to top)Early breast cancer causes no symptoms and is not painful. Usually breast cancer is discovered before any symptoms are present, either on mammography or by feeling a breast lump. A lump under the arm or above the collarbone that does not go away may be present. Other possible symptoms include breast discharge, nipple inversion and changes in the skin overlying the breast.
Screening
(back to top)Due to the high incidence of breast cancer among older women, screening is now recommended in many countries. Screening methods suggested include breast self-examination and mammography. Only mammography has been proved to reduce mortality from breast cancer. In some countries routine (annual) mammography of older women is encouraged as a screening method to diagnose early breast cancer.
Mammography is still the modality of choice for screening of early breast cancer. Magnetic resonance imaging (MRI) has been shown to detect cancers that are not visible on mammograms, but it has several disadvantages. For example, although it is more sensitive, it is less specific than mammography. As a result, MRI studies will have more false positives, which may have undesirable financial and psychological costs. It is also a relatively expensive procedure, and one which requires the intravenous injection of a chemical agent to be effective. It may be valuable for younger women, whose breasts are denser with less fat and more connective tissue, making it harder to spot cancers on mammograms. Ultrasound alone is not adequate as a screening tool but it is a useful additional investigation, especially for the characterization of benign tumours.
The U.S. National Cancer Institute recommends screening mammography with a baseline mammogram at age 35, mammograms every two years beginning at age 40, and then annual mammograms beginning at age 50. In the UK, women are invited to attend for screening once every three years beginning at age 50. Women with one or more first degree relatives (mother, sister, daughter) with premenopausal breast cancer should begin screening at an earlier age. It is usually suggested to start screening at an age that is 10 years less than the age at which the relative was diagnosed with breast cancer.
Breast cancers detected by mammography are usually smaller than those detected clinically, and women who undergo mammography are more likely to be eligible for breast-conserving therapy.
Treatment
(back to top)The mainstay of breast cancer treatment is surgery when the tumor is localized, with possible adjuvant hormonal therapy (with tamoxifen or an aromatase inhibitor), chemotherapy, and/or radiotherapy. At present, the treatment recommendations after surgery (adjuvant therapy) follow a pattern. This pattern may be adapted as every two years a worldwide conference takes place in St. Gallen, Switzerland to discuss the actual results of worldwide multi-center studies. Depending on clinical criteria (age, type of cancer, size, metastasis) patients are roughly divided to high risk and low risk cases which follow different rules for therapy. Treatment possibilities include Radiation Therapy, Chemotherapy, Hormone Therapy, and Immune Therapy.
An online resource for helping to quantify the relative risks and benefits of chemotherapy v. hormonal therapy is Adjuvant! Online (see below).
In planning treatment, doctors can also use a test called Oncotype DX that measures breast cancer recurrence risk.
The emotional impact of cancer diagnosis, symptoms, treatment, and related issues can be severe. Most larger hospitals are associated with cancer support groups which can help patients cope with the many issues that come up in a supportive environment with other people with experience with similar issues.
Online cancer support groups are also very beneficial to cancer patients, especially in dealing with uncertainty and body-image problems inherent in cancer treatment.
Surgery
(back to top)Standard practice requires that the surgeon must establish that the tissue removed in the operation has margins clear of cancer, indicating that the cancer has been completely excised. If the tissue removed does not have clear margins, then further operations to remove more tissue may be necessary. This may sometimes require removal of part of the pectoralis major muscle which is the main muscle of the anterior chest wall.
During the operation, the lymph nodes in the axilla are also considered for removal. In the past, large axillary operations took out ten to forty nodes to establish whether cancer had spread - this had the unfortunate side effect of frequently causing lymphedema of the arm on the same side as the removal of this many lymph nodes affected lymphatic drainage. More recently the technique of sentinel lymph node dissection has become popular as it requires the removal of far fewer lymph nodes, resulting in fewer side effects.
Radiation therapy
(back to top)Radiation therapy consists of the use of high powered X-rays or gamma rays that precisely target the area that is being treated. These X-rays or gamma rays are very effective in destroying the cancer cells that might recur where the tumor was removed. These X-rays are delivered by a machine called a linear Accelerator or LINAC. The use of radiation therapy for breast cancer is usually given after surgery has been performed and is an essential component of breast conserving therapy. The purpose of radiation is to reduce the chance that the cancer will recur.
Radiation therapy works for breast cancer by eliminating the microscopic cancer cells that may remain near the area where the tumor was removed during surgery. Since by the nature of radiation and its effects on normal cells and cancer cells alike the dose that is given is to ensure that the cancer cells are eliminated. However, the dose cannot be given in one sitting. Radiation causes some damage to the normal tissue around where the tumor was but normal healthy tissue can repair itself. The treatments are given typically over a period of five to seven weeks, performed five days a week. Each treatment session takes about fifteen minutes per day. Breaking the treatments up over this extended period of time gives the healthy normal tissue a chance to repair itself. Cancer cells do not repair themselves as well as normal cells, which explains the efficacy of radiation therapy.
Side effects of radiation therapy
(back to top)- reddening of the skin
- muscle stiffness
- mild swelling
- tenderness in the area
- long term shrinking of the irradiated breast
Along with improved cosmetic outcome of treatment with radiation there are also other techniques for delivering radiation to the breast. One such new technology is using IMRT (intensity modulated radiation therapy) which the radiation oncologist can change the shape and intensity of the radiation beam at different points across and inside the breast. This allows for an even more focused beam of radiation directed at the tumor cells and leaving most of the healthy tissue unaffected by the radiation
Another new procedure involves a type of brachytherapy where a radioactive source is temporarily placed inside the breast in direct contact with the tumor bed (area where tumor was removed). This technique is called a Mammosite and is currently undergoing clinic trials.
Systemic therapy
(back to top)Chemotherapy
(back to top)There are several different chemotherapy regimens that may be used. The determination of which regimen will be used depends on many factors including the character of the tumor, lymph node status, and the age and health of the patient. Possible chemotherapy regimens include:
- CMF: cyclophosphamide, methotrexate, and 5-fluorouracil
- FAC: 5-fluorouracil, doxorubicin, cyclophosphamide
- AC: doxorubicin and cyclophosphamide
- AC with paclitaxel administered after the AC
- TAC: docetaxel , doxorubicin, and cyclophosphamide
- FEC for three cycles followed by docetaxel for three cycles
- Dose dense AC: doxorubicin and cyclophosphamide followed by paclitaxel
Since chemotherapy effects the production of white blood cells a growth factor e.g. pegfilgrastim is sometimes administered along with chemotherapy.
Chemotherapy has increasing side effects as the patient's age passes 65.
Hormonal treatment
(back to top)Patients with estrogen receptor positive tumors will typically receive a hormonal treatment after chemotherapy is completed. Typical hormonal treatments include:
- Tamoxifen is typically given to premenopausal women to block estrogen the reception of estrogen by breast cancer cells
- Aromatase inhibitors are typically given to postmenopausal women to lower the amount of estrogen in their systems
- GnRH-analogues
Immune treatment
(back to top)In patients whose cancer expresses an over-abundance of the HER2 protein the drug trastuzumab (Herceptin ®) is used to block the HER2 protein in breast cancer cells slowing their growth. This drug was originally used only in the treatment of patients with metastatic disease, however in the summer of 2005 two large clinical trials published results suggesting that patients with early stage disease also benefit significantly from Herceptin.
Prognosis
(back to top)There are several prognostic factors associated with breast cancer. Stage is the single most important prognostic factor in breast cancer, as it will take into consideration local involvement, lymph node status and whether metastatic disease is present or not. The higher the stage at the time of diagnosis, the worse the prognosis of breast cancer is. Node negative breast cancer patients have a much better prognosis compared to node positive patients.
Presence of estrogen and progesterone receptors in the cancer cell is another important prognostic factor, and may guide treatment. Hormone receptor positive breast cancer is usually associated with much better prognosis compared to hormone negative breast cancer.
HER2/neu status has also been described as a prognostic factor. Patients whose cancer cells are positive for HER2/neu have more aggressive disease and may be treated with trastuzumab, a monoclonal antibody that targets this protein.
Ashkenazi Jewish women and black women tend to have higher rates of fatalities.
Prevention
(back to top)Prevention of breast cancer in high-risk women is probably more important than treatment of breast cancer. Many women who may have inherited genetic mutations in breast cancer related genes (called BRCA1 and BRCA2) might have very high risk of developing breast cancer. In these women and other women who have very strong family history of breast cancer, the chance of developing breast cancer may be decreased by hormonal treatment . Classic drug for breast cancer prevention is tamoxifen, which is currently used extensively in high risk women. A recent clinical trial has shown that Raloxifene, which is drug commonly used for prevention of osteoporosis is as good as tamoxifen in breast cancer prevention with much less side effects
Prophylactic oophorectomy (removal of ovaries), post-child-bearing, reduces the risk of developing breast cancer by 50%, as well as reducing the risk of developing ovarian cancer by 96%.
Breast cancer in males
(back to top)For years the medical profession assumed that male breast cancer was significantly different from female breast cancer. Today they are grouped together and receive the same treatment regimens. Since the male breast tissue is confined to the area directly behind the nipple, treatment for males has always been a mastectomy. Since the psychological effects of this surgery are just as great for males as for females, experimental surgery has been started to introduce the lumpectomy for males.
The incidence of breast cancer in males is very low, possibly due to the different endocrine milieu or the small total amount of glandular tissue. Seminal research in recognizing the incidence of male breast cancer was performed by the U.S. military at
Breast cancer awareness
(back to top)In the month of October, breast cancer is recognized by survivors, family and friends of survivors and/or victims of the disease. A pink ribbon is worn to recognize the struggle that men and women face when battling the cancer.
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors(see full disclaimer). Donate to Wikipedia.This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Breast_Cancer".
