Cancer is a disease where the normal cellular regulators malfunction and instead of the cells dying off as programmed they continually divide without their normal control, accumulating into a mass (tumour). As the tumour grows, it promotes the formation of blood vessels to bring in oxygen and nutrients, however these vessels are ‘leaky’ and can allow the cancer cells to leave the tumour site and travel through the blood stream and lymphatic system to other parts of the body. This process is called metastasis. It is thought that the majority of breast cancers develop as the end result of a continuum of change within the breast tissue as depicted below. These changes usually take many years to progress to invasive carcinoma, and many never progress that far.
• Pre-Invasive Breast Cancer (ductal carcinoma in situ)
The major difference between DCIS and invasive breast cancer is that the cancer cells have not yet developed the ability to invade and are thus contained within the breast duct in which they arise and, as such, cannot spread or metastasise. DCIS is almost always impalpable and is detected primarily through mammography which allows us to detect breast cancer at the earliest rather than more advanced stage.
• Invasive Breast Cancer
The majority of these arise in the breast ducts (70%) and are therefore known as ductal cancers (or NOS). About 20% of cancers develop in the glands at the ends of the ducts and are called lobular cancers. The remaining 10% are called special type cancers and are discussed later. These two main types of breast cancer tend to behave in a similar fashion although lobular cancers are more often multifocal (more widespread throughout the breast rather than causing an obvious mass - thus accounting for the increased difficult in detection mammographically) and bilateral (in both breasts). The most important factors in determining how well the cancer will behave is thus not the tumour type but its prognostic features.
• Prognostic features
There are 3 major prognostic features, which can be combined into an index to give an indication of disease severity (the Nottingham Prognostic Index -NPI) although this must be interpreted with some caution as the index is a statistical value that cannot tell you how you will fare (only the average outcome for 100 women with identical disease). The pathology report will contain information on all of features:
1. lymph node involvement
2. histological grade: I, II, III
3. tumour size
There are also several other prognostic features which include:
1. oestrogen/progesterone receptor status (ER /PR)
2. herceptin receptor status (HER2)
3. proliferation markers, (eg Ki67)
4. basal phenotype
5. tumour subtype (ductal, lobular, etc)
6. lymphovascular invasion -- LVI (presence of tumour cells in the small vessels around the tumour, in transit to the lymphnodes)
• Special Type Cancers
As mentioned previously, these account for about 10% of cancers. The majority are less aggressive than ductal cancers per se, with the exception of inflammatory carcinomas:
5. adenoid cystic
Whilst these tend to present as breast lumps, with the final diagnosis often only confirmed on histology, inflammatory carcinomas deserve special mention. Blockage of the skin lymphatic channels leads to swelling and redness and thus it can be mistaken for a breast infection.
Paget’s disease, whilst not a special type of cancer, also presents in an unusual way with nipple crusting and bleeding and can be mistaken for eczema of the nipple. The underlying cause is either DCIS or an invasive carcinoma affecting the ducts behind the nipple.
• Clinical Staging
There are 2 main clinical staging systems:
(1) TNM: (where T is for Tumour size, N is for lymph Node involvement and M is for Metastasis) which can be both a clinical & histological staging system. It is important as a way of accurately describing the tumour and, for example, allowing similar groups to be analysed to assess outcomes in treatment trials.
(2) Manchester system: which is a clinical staging method describing whether or not the tumour is confined to the breast.
Surgery is still the mainstay of treatment. Whever possible breast conserving surgery rather than mastectomy is preferred Modern oncoplastic techniques aim to maintain quality of life and an acceptable breast appearance whilst at the same time being uncompromising in oncological effectiveness. In more recent years this has been aided with the use of neoadjuvant chemotherapy (prior to surgery) to shrink the tumour.
• Breast Conserving Surgery
In this procedure, variously known as lumpectomy, wide local excision, quadrantectomy or partial mastectomy, the pre-cancer or cancer is removed together with a surrounding margin of normal breast tissue. This can often be accomplished through a discrete incision placed around the areola. By mobilising the breast tissue under the skin the appearance from the resultant volume deficit can be minimised. An uninvolved (clear) margin is important to prevent recurrent disease in the future. Because of this it is sometimes necessary to recommend further surgery once the histology report is available. Radiotherapy is almost always recommended afterwards to the breast.
A mastectomy means that much of the breast skin and all the breast tissue is removed. If appropriate a new breast can be reconstructed, ideally at the time of surgery. If reconstruction is not performed a flat scar overlying the chest wall will be the result and an external prosthesis can be worn inside the bra. Radiotherapy is usually not a requirement postoperatively, although this is assessed on an individual basis.
• Lymph nodes
This is a standard part of breast cancer surgery unless the diagnosis is pre-cancer (DCIS). As a rule if breast cancer spreads beyond the breast it is trapped in the axillary (armpit) lymph nodes first. In the majority of people a sentinel node biopsy is performed, with the removal of one or two nodes, rather than all of them. This is undertaken both to determine (stage) whether the breast cancer has spread to the lymph nodes and to remove any affected nodes.
• Recovery Time
Everyone recovers from an operation at different rates but the majority of women feel essentially back to normal after a couple of weeks. Gentle exercise during convalescence is encouraged and as long as it does not hurt you will not do any damage.
Following surgery your results should be discussed by the multidisciplinary team (MDT), which comprises of specialists in surgery, radiology, pathology, oncology, radiotherapy, etc. This allows for a full review of your preoperative and operative course and determination of your optimal postoperative treatment. This MAY comprise of ANY OR ALL of the following:
The majority of breast cancers respond to oestrogen (ER+). Aromatase inhibitors such as Letrozole & Femara prevent the production of oestogen in post menopausal women. Another option is Tamoxifen which blocks the action of oestrogen.
If your cancer was ER+ taking hormonal therapy can reduce both the chance of cancer returning and of cancer in the other breast. Treatment is for 5-10 years.
Radiotherapy is well tolerated without significant side effects, in particular it will not cause hair loss or sickness. The radiotherapy treatment lasts for up to five weeks requiring you to attend every weekday, although only for a matter of minutes. The radiotherapy 'sterilises' the remaining breast tissue reducing the chance of future cancer in this breast to about 5% at five years.
Chemotherapy drugs interfere with the process of cell division/multiplication so the cells can't divide and as a result die off. The idea is to decrease the total number of cancer cells enough for your immune system to be able to deal with.
Different drugs interfere in this process at different points, so often more than one kind of drug is used at a time. Unfortunately this effect is not very selective. It acts on all cells, not just cancer cells, that are rapidly dividing - including hair follicles, bone marrow, ovaries and stomach. The bone marrow produces red blood cells, white blood cells and platelets and chemotherapy slows this down. Chemotherapy is given in cycles to allow the bone marrow to recover as well as to target different populations of cancer cells.
A minority of cancers are called Herceptin positive (HER2+). For these there is a newer drug (a monoclonal antibody) that is usually given after chemoptherapy. It does not have the same side effects as chemotherapy. Treatment is usually for 12 months.