Breast cancer is New Zealand’s third most common cancer. About 3300 women and 25 men are diagnosed each year.
Breast cancer is New Zealand’s third most common cancer. Nearly 3,500 women are diagnosed with breast cancer each year, with more than 600 dying from the disease.
Breast cancer has a higher survival rate if found earlier. According to the Breast Cancer Foundation, if cancer is detected by regular screening mammogram, the 10 year survival rate is 95%. If cancer is detected when a lump is found, the 10 year survival rate is 85 per cent. Treatment generally involves surgery followed by a combination of other treatments such as chemotherapy or radiotherapy.
Breast cancer occurs when breast cells develop abnormally and grow out of control forming a malignant (cancerous) tumour. It is possible for cancer cells to spread (metastasise) from the breast to other parts of the body via the lymphatic system and by direct entry into the blood stream. Once the cancer cells have reached other parts of the body, they are called metastases.
Men, trans-women and intersex and non-binary people can also get breast cancer.
Causes and risk factors
The lifetime risk for New Zealand women for developing breast cancer is one in nine. There are risk factors that women can and can’t change. The main risk factors for developing breast cancer that you cannot change are:
- Increasing age – breast cancer is not common in individuals under 50
- Having a history of close family members (mother, sister, daughter) with breast cancer
- Having had breast cancer previously.
- Having had a biopsy showing an "at risk" breast lump or thickening
- Having a genetic risk, such the BRCA1 or BRCA2 gene mutations.
BRCA1 (BReast CAncer gene 1) and BRCA2 (BReast CAncer gene 2) are genes that produce proteins that help repair damaged DNA. Inheritance of harmful mutations in one of these genes is associated with an increased risk of breast cancer. About 13 per cent of women in the general population will develop breast cancer at some point during their lives. In contrast, 55 to 72 per cent of women who inherit a harmful BRCA1 mutation and 45 to 69 per cent of women who inherit a harmful BRCA2 mutation will develop breast cancer by age 70 to 80 years.
Māori women experience higher than average rates of breast cancer, and Māori and Pasifika women are more likely to develop breast cancer at a younger age.
Risk factors that you can change are:
- Being overweight or obese, especially after menopause
- Having a low level of physical activity
- Alcohol consumption
- A diet high in fat and a reduced intake of fibre, fruits, and vegetables
- Certain medications such as oral contraceptives may increase risk in individuals with a history of breast cancer or known gene mutations.
There are also some popular myths that are not risk factors for developing breast cancer:
- Trauma to the breast – sometimes people may discover a lump due to a blow or injury to the breast, but this is not associated with cancer
- Underwire bras
- Mobile phones
- Breast implants (Textured silicone implants have been associated with a small risk of a very rare cancer of the immune system called Anaplastic Large Cell Lymphoma. If you have concerns or questions, talk with your plastic surgeon).
Types of breast cancer
Breast cancer Pre-invasive is also known as in situ carcinoma and Stage 0 cancer, and are pre-cancers that are non-invasive. This means the abnormal cells have not developed the ability to spread to other parts of the breast or outside of it. It is not possible to predict if or when in-situ carcinoma will develop into breast cancer.
There are two types of in situ carcinoma: Ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS). Treatment depends on the type of abnormal cells and its location. This can be regular surveillance with breast checks and mammograms to surgery or radiation. Chemotherapy is typically not used.
Also known as invasive carcinoma, this is breast cancer where the abnormal cells have spread into surrounding tissues and have the potential to spread throughout the body. The main two types of breast cancer are invasive carcinoma no-special-type (also known as ductal) and lobular carcinoma.
Other less common breast cancers include inflammatory breast cancer, Paget’s disease of the breast, mucinous or colloid carcinoma, tubular carcinoma, and medullary breast cancer. The treatment depends on the type of cancer and the extent of the disease (known as staging).
Signs and symptoms
If breast cancer is found outside of regular screening mammograms, the first sign of breast cancer is usually a new, painless lump in the breast. Other signs of breast cancer include:
- A new area of thickened tissue in the breast
- Nipple discharge or a change in the nipple
- Peeling, crusting, or flaking of the skin around the nipple
- Dimpling or puckering of the skin of the breast
- A change in breast size or shape
- Swelling or discomfort in an armpit.
While these symptoms may not be related to breast cancer, it is important to see a doctor promptly for assessment and accurate diagnosis if any of these symptoms are present. Early detection is vital in the successful treatment of breast cancer.
If a suspicious area is found on mammogram, or you have an abnormal lump or other symptoms are present, a referral to a breast specialist for assessment will probably be recommended. In order for an accurate diagnosis to be made you may undergo clinical examination, imaging (mammography, ultrasound, CT, or MRI), and/or biopsy.
There are different types of biopsies used to take cell or tissue samples from a suspicious lump so they can be sent to a laboratory for analysis under a microscope.
- A fine needle aspiration is usually the first type of biopsy used. It is performed using a local anaesthetic and involves inserting a fine needle into the lump and removing a small sample of cells and/or fluid. Ultrasound may be used to guide the insertion of the needle.
- Other biopsy procedures may be done with larger needles or small incisions. Imaging machines will guide the specialist to the area where a tissue sample, or the whole lump, is removed.
If a diagnosis of breast cancer is made, blood tests, x-rays, and scans of the bones and liver may be performed to assess if the cancer has spread to other organs.
Stages of breast cancer
After diagnosis, breast cancers are assigned a "stage". The stage indicates the tumour's size and how far it has spread within the breast, the axillary lymph nodes in the armpit (see picture), or to other organs in the body.
Invasive breast cancer stages range from I to IV – a higher stage indicates more severe cancer.
- Stage I: These tumours measure less than two centimetres. The axillary lymph nodes are not affected and there are no signs that the cancer has spread elsewhere in the body.
- Stage II: These tumours measure between two and five centimetres, or the axillary lymph nodes are affected, or both. There are no signs that the cancer has spread elsewhere in the body.
- Stage III: These tumours are larger than five centimetres, the axillary lymph nodes are usually affected, but there are no signs that there has been any further spread.
- Stage IV: These tumours are of any size, but the axillary lymph nodes are usually affected and the cancer has spread to other parts of the body.
Breast cancer tumours are also classified as being "hormone receptor positive" or "hormone receptor negative". Approximately 60% of all breast cancer tumours are hormone receptor positive meaning that they rely on oestrogen or progesterone to grow. The hormone receptor status of the tumour will be considered when treatment is planned.
Another classification given is the HER2 status of the cancer. HER2 is a protein that influences a cell’s growth and reproduction. In HER2 positive breast cancers, there are an abnormally large number of HER2 proteins on the cancer cells that cause them to grow and spread at a faster rate. Approximately 20% of all breast cancers are classified as HER2 positive. HER2 status will be considered when treatment is planned.
Treatment of breast cancer depends on the type of breast cancer, its size and position, whether it has spread, the individual’s age and general health, and the individual’s preference. In general, some type of surgery is recommended followed by additional treatments.
Lumpectomy / partial mastectomy:
In most cases, the breast cancer tumour can be removed without having to remove the entire breast (referred to as breast conserving surgery). The area of the cancer is removed along with a ''margin" of healthy surrounding tissue (usually about 1cm), to ensure that all of the breast cancer is removed.
This operation involves removing the entire breast and all of the breast tissue from just below the collarbone to the upper abdomen. A "simple mastectomy" is when just breast tissue is removed. A "modified radical mastectomy" is when the lymph glands under the arm are also removed.
Mastectomy may be recommended if the tumour is large, there is more than one area of cancer in the breast, or for cases of recurrent breast cancer.
Surgical treatment may also involve:
Sentinel node biopsy:
This type of lymph node biopsy is used in some cases to minimise problems associated with axillary node dissection. During a sentinel node biopsy dye is injected around the breast cancer tumour. The dye drains through the lymph vessels and into the first node to be involved - the sentinel node. This node is then removed for analysis. If the sentinel node is clear of cancer cells, then it can safely be presumed that the cancer has not spread to the rest of the axillary nodes. If the sentinel node is positive for cancer cells a subsequent procedure to remove the remaining lymph nodes would be needed.
Axillary node dissection:
It is usual practice during breast cancer surgery to remove up to half of the axillary lymph nodes for testing. Testing of the lymph nodes can indicate whether the cancer has spread into the lymphatic system, increasing the cancer stage.
Whether to undergo a breast reconstruction is a choice for women to consider. Women who choose not to have reconstruction, can consider using an external breast prosthesis to give the appearance of a normal breast. This is a breast-shaped mould that fits into a specially fitted bra and comes in a variety of shapes and sizes. Wearing the prosthesis also helps to maintain proper balance and posture. Women who choose reconstruction can have it done at the time of their mastectomy or at a later date. A plastic surgeon usually performs the surgery. The aim of breast reconstruction is to recreate a breast that feels and looks as natural as possible. Occasionally the healthy breast needs to be made smaller to match the breast that has been reconstructed. This surgery would be performed at the same time as the breast reconstruction.
Additional treatments are commonly given after surgical removal of a breast cancer. This can be called “adjuvant” therapy. One or a combination of these treatments may be recommended. An oncologist (cancer specialist) will be involved in deciding which treatments will be given.
This uses radiation to destroy any cancer cells that may be left in the breast. It is most commonly used after lumpectomy or partial mastectomy. However, it may be used after mastectomy if there was more than one tumour, the tumour was large, or the tumour was growing close to the chest wall. A course of radiotherapy is usually given over 4–6 weeks, consisting of daily treatments from Monday to Friday. Side effects of the treatment may include severe tiredness and burns similar to bad sunburn on the treated area.
This may be given if the cancer has high-risk of spread, which is determined by a combination of clinical and laboratory tests. Chemotherapy medications can be given by tablet or as injections into the blood stream. Usually it is a combination of both. The medications aim to kill off any cancer cells that may be circulating in the body. There are different strengths and combinations of chemotherapy medications, which are given in cycles. Side effects of chemotherapy treatment may include nausea, hair loss, sores in the mouth, and diarrhoea.
For cases where the breast cancer is hormone receptor positive, hormone therapy may be prescribed to help prevent recurrence of the breast cancer. These medications work by blocking the hormone receptors on the breast cancer cells, preventing hormones binding to them and stimulating growth. One common example of this type of medication is tamoxifen.
These medications are formulated to target cancer cells, rather than normal healthy cells. Trastuzumab (Herceptin) is the most widely used targeted therapy currently available in New Zealand. Others are in development or clinical trials. Trastuzumab is used to treat early and advanced HER2-positive breast cancer. It binds to the HER2 proteins, preventing them from stimulating the cancer cells to grow. It also acts to “flag” the cancer cells to the body, which then stimulates the immune system to destroy the abnormal cells.
After the diagnosis and treatment of breast cancer, regular follow up visits with the healthcare specialists involved in the treatment will be scheduled. This will include seeing the oncologist and surgeon. Initially this may be as frequently as every three months but will eventually be less often. During these visits monitoring procedures such as imaging (i.e. mammograms or ultrasounds), blood tests, and clinical examinations may be conducted.
Other healthcare professionals who may be involved in the on-going care and monitoring include a GP, a breast physician, breast care nurse, and physiotherapist.
Some women may find it beneficial to see a counsellor to help them deal with the emotional and psychological impact of the breast cancer diagnosis and the implications of treatment.
As the cause of breast cancer is unknown, the condition cannot be prevented as such. However, there are things women can do that may reduce their risk of developing breast cancer and/or detect the cancer early.
Women aged from 45 to 69 years are eligible for free mammograms through the Breast Screen Aotearoa national screening programme every two years.
If you are under 45 years of age and in a high-risk group, talk to your doctor about screening options. A mammogram is not generally recommended as a regular screening tool for women under 40 as its results are less reliable in that age group.
Breast self-examination (BSE):
It is recommended that women check their own breasts regularly by feeling for lumps and thickening tissue, and looking in the mirror for changes to shape, skin or the nipples. This enables them to learn what their breasts are like normally so that they are better able to detect any changes or abnormalities in the breast.
Eating a diet low in fat, undertaking regular exercise, and limiting alcohol intake may help to reduce the risk of breast cancer. Being overweight or obese, especially after menopause, increases the risk of breast cancer. This is because fat cells make oestrogen, and oestrogen can cause certain types of breast cancer to develop.
Risk reducing surgery:
In rare cases, where there is a strong family history of breast cancer or other factors such as a cancer gene or previous breast cancer, a woman may choose to have both breasts removed – usually with breast reconstruction. This will reduce her chances of developing breast cancer. However, it is possible for the cancer to develop in remaining breast tissue.
Further information and support
The following organisations can offer further information, support and resources about breast cancer.
Breast Cancer Support (BCS)
BCS is an organisation of survivors of breast cancer who provide information and support.
Freephone: 0800 273 222
This free national mammography service helps check for early breast cancer. BreastScreen Aotearoa is one of the National Screening Unit’s six screening programmes. The programme is offered to all women in New Zealand aged 45-69 years who have no symptoms.
Freephone: 0800 270 200
Email: [email protected]
Breast Cancer Aotearoa Coalition
This organisation, which is run by breast cancer survivors, provides support and information to those diagnosed with breast cancer to help them make informed choices about their treatment.
Cancer Society - Cancer Information Helpline
Staffed by specialised cancer nurses, this service provides free information and support in relation to all types of cancers including breast cancer.
Freephone: 0800 CANCER (0800 226 237)
Email: [email protected]
Look Good Feel Better
This registered charity offers free community-based programmes to help cancer patients connect and restore appearance and self-image when coping with the side effects of cancer treatment. Group workshops are held nationwide.
Freephone: 0800 865 432
Email: [email protected]
Provides support and information to help improve the quality of life for women with incurable breast cancer.
Freephone: 0800 11 22 77
Email: [email protected]
Breast Cancer Foundation NZ
This organisation aims to educate women and the wider community about breast cancer. It also stages fundraising and awareness events.
Freephone: 0800 902 732
Email: [email protected]
Cancer Council Australia (2018). Understanding breast cancer (Booklet). Sydney: Cancer Council Australia. https://www.cancer.org.au/content/about_cancer/ebooks/cancertypes/Understanding_Breast_Cancer_booklet_July_2018.pdf
Cancer Society of New Zealand (2012). A Guide for women with breast cancer (Information Sheet). Wellington: Cancer Society NZ. https://auckland-northland.cancernz.org.nz/assets/Cancer-information-2/IS-Guide4WomenwithBreastCancer-13Feb2012.pdf
Ministry of Health (2016). Cancer: New registrations and deaths 2013 (Report). Wellington: New Zealand Ministry of Health. https://www.health.govt.nz/system/files/documents/publications/cancer-new-registrations-deaths-2013-nov16.pdf
Ministry of Health (2019). Breast Cancer (Web Page). https://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/breast-cancer [Accessed 20 August 2019]
National Cancer Institute (2018). BRACA mutations: Cancer risk and genetic testing (Web Page). Bethesda, MD: National Cancer Institute at the National Institutes of Health. https://www.cancer.gov/about-cancer/causes-prevention/genetics/brca-fact-sheet [Accessed: 23/07/19]
Breast Cancer Foundation NZ (2019). Risk factors (Web Page). Auckland: Breast Cancer Foundation NZ. http://www.nzbcf.org.nz/BREASTCANCER/RiskFactors.aspx [Accessed: 23/07/19]
Breast Cancer Foundation NZ (2019). Breast cancer in NZ (Web Page). Auckland: Breast Cancer Foundation NZ. http://www.nzbcf.org.nz/BREASTCANCER/Overview/BreastCancerinNZ.aspx [Accessed: 23/07/19]
Breast Cancer Foundation NZ (2019). Treatment options (Web Page). Auckland: Breast Cancer Foundation NZ. https://www.breastcancerfoundation.org.nz/breast-cancer/treatment-options [Accessed: 23/07/19]
Breast Cancer Network Australia (2019). Myths about breast cancer (Web Page). https://www.bcna.org.au/breast-health-awareness/myths-about-breast-cancer/ [Accessed 23/8/19]
Last Reviewed – December 2022
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