Breast cancer is the most common cancer in women, and second most common cause of death from cancer.
There are more published studies (on PubMed) on breast cancer, than on any other disease.
Breast cancer is broadly classified as:
- Ductal – tumours arising from the epithelial lining of the ducts
- This is by far the most common type
- Lobular – tumours arising from the epithelial lining of the terminal ducts of the lobules
In the UK, a woman has a 1/9 chance of developing breast cancer
- Incidence about 95 per 100 000
- Mortality of about 23 per 100 000
- Gives a mortality rate of about 25%
- Mortality rate is decreasing due to earlier diagnosis (from screening) and improved treatments
- About 5% are metastatic at the time of diagnosis
It is the most common cause of death in women aged 35-55
- The most common cancer in females
- In other developed countries (e.g. Australia) it is the most common cancer in women
- Incidence increases with age
- <5% of cases in women <35
- 25% in women <50
It is responsible for 20% of all cancer in women
- Gynaecomastia +/- cirrhosis
- Family history
- Hormonal disorders
Increased risk with age
Oestrogen exposure – long, uninterrupted periods
Large gap between menarche and menopause
- Early first period
- Late menopause
- Women with 40 years of active menstruation have 2x the risk of those with 30 years
- First pregnancy at age >30 years
- HRT with oestrogen only – little to no increased risk
- HRT with oestrogen and progestogen increases the risk of breast cancer
- Increased risk is related to the period of use of HRT. Risk reduces after HRT is stopped. Risk if <5 years of HRT is thought to be minimal.
- The Pill
- Risk thought to be very low
- Correlated to the age at which the pill is ceased (older age = greater risk) rather than the duration of use of the pill
- 10 years after ceasing the pill the risk has returned to baseline
- Not breast-feeding
- Radiation to the chest
- Obesity / high fat diet / alcohol
- Increases the risk particularly in those over 60
- Breast augmentation is NOT correlated with an increased risk of breast cancer
- BRCA1 and BRCA2 genes
- Account for about 5% of breast cancers
- Mutation on chromosome 17
- Lifetime risk of breast cancer is about 75%
- Lifetime risk of ovarian cancer is about 50%
- Men with the gene also at increased risk
- Mutation on chromosome 13
- Lifetime risk of breast cancer 40-85%
- Lifetime risk of ovarian cancer <25%
- Lifetime risk of breast cancer for men is about 6%
Atypical epithelial hyperplasia
- Highest incidence in the ‘Western World’ i.e. North America, Europe, Australia, NZ. Incidence is lowest in Africa and South-East Asia
- These variation are probably the result of the other above risk factors, e.g. in these western countries, menarche is likely to be earlier, first pregnancy likely to be later, diets high in processed foods, alcohol intake and post menopausal weight likely to be greater.
BRCA1 – on chromosome 17, accounts for around 50% of familial cases that appear to be inherited in an autosomal dominant fashion.
- 60-85% lifetime risk of breast cancer.
- Also increased risk of bowel cancer, ovarian cancer (50% lifetime risk) and prostatic cancer (men)
BRCA2 – on chromosome 13 – less common than BRCA1, accounts for 30-40% of familial cases.
- Similar lifetime risk to BRCA1
- Increased risk of ovarian cancer (25% lifetime risk), but risk of other cancers compared to risk of other cancers from BRCA1
- Men with BRCA2 have a 6% chance of developing breast cancer (100x greater than the normal population)
Both BRCA1 and BRCA2 are tumour suppressor genes, responsible for the production of proteins which help repair damaged DNA during cell reproduction. In the mutated forms of these genes, the protein produced is ineffective, allowing DNA defects to accumulate over time.
- Typically, mutated BRCA1 genes produce a protein that is too short, and is unable to perform the normal repair process.
- There are hundreds of different mutations – but all have the same result
- Most people only have one defective copy and one normal copy
- Those who have two copies of BRCA2 will also have:
- There is also an increased risk of ovarian cancer in women with BRCA1 and BRCA2, but the risk is less with BRCA2.
- HER2 mutation occurs in about 20% of breast cancers
- It is associated with a worse prognostic outcome
- Has specific treatment in the form of the monoclonal antibody Trastuzumab (Herceptin). This will bind to the receptor, and cause the production of p27 within the cell, which reduces cell proliferation
- As a result of this specific treatment, breast cancers are routinely tested for HER2/neu presence.
- HER2 expression is reduced by the presence of oestrogen. In some tumours treated with tamoxifen, HER2 expression can increase.
- Nipple changes
- Skin tethering
- Tethering to underlying tissues, e.g. muscle
- Ulceration (late sign)
- Oedema / erythema
Originally set up in 1988. Costs £75m per year (roughly £45 per woman screened, or £37 per woman invited).
The programme is run on a three yearly rotation basis depending on the GP practice, which means the first invitation for screening will be received any time after the woman’s 50th birthday, but before the 53rd.
After a woman reaches the upper age limit (70), then invitations are not routinely sent, but women are still encouraged to and entitled to make their own NHS appointments if they wish.
It is estimated that the screening program saves around 1400 lives per year (or 1 in every 500 women screened). This is roughly a 35% reduction in mortality when compared to a non-screened population.
Screening is also available for women under 50 who:
- Have had a previous cancer
- Have had a first degree relative with cancer <50 years
- Have a known BRCA1, BRCA2 or TP53 gene
- Is typically performed every 2 years (unlike the UK which is every 3 years)
- Offered to all women aged 50-74
- Should be offered to women aged 40-49 with:
- Moderately increased risk (see below)
- Consider screening every year in people with moderately increased risk
Moderately increased risk
Affects about 4% of the population. Defined as:
- x1 first degree relative with a breast cancer diagnosis at age <50
- >1 first degree relative with breast cancer diagnosis at any age
Potentially High risk
Affects about 1% of the population. Defined as:
- Women with TWO 1st OR 2nd degree relative with BREAST or OVARIAN cancer PLUS at least one of the following:
- >2 relatives affected
- Breast cancer diagnosed at <40 years
- Bilateral breast cancer
- Breast and ovarian cancer in the same woman
- Jewish ancestry
- Breast cancer in a male relative
- One 1st or 2nd degree relative with breast cancer diagnosis at <45 years PLUS relative on same side of family with sarcoma at age <45
- Family member with known high risk breast cancer gene (BRCA1 or BRCA 2)
Mammography – an x-ray of the breast tissue. Usually front and lateral images of the breast are taken.
- It is not effective at detecting the early changes of breast cancer in women <35 years – as their breast tissue is more dense, and thus the subtle density changes of early dysplasia cannot be seen. USS is used in women <35
- Sensitivity – 75-95%
- Specificity –95%
- It is usually a bit uncomfortable, and in some women it may cause pain. One study suggests that good explanation of the procedure beforehand reduces the perception of pain. Taking aspirin or paracetomol before the procedure does not alter the perception of pain.
- Sometimes products on the skin (e.g. deodorant, talcum powder) may appear as calcifications.
- Results usually described to the patient within 1-2 weeks, but can take up to 4.
- 5% (1 in 20) screened women are called back for further review – but only about 13% of these (or, about 0.65% of the total) will actually have cancer. So, for every 8 women called back for review, only 1 of them will have cancer.
Digital Mammography – FFDM – Full field digital mammography – a newer technique, that provides higher resolution imaging, and in theory is more sensitive in younger women with more dense breast tissue. However, in trials, FFDM has not been shown to be any more effective at detecting cancer than traditional mammography, and it is not routinely used.
MRI – MRI scanning is recommended by NICE for some women with a very high risk (e.g. known gene defects), as it is more sensitive, but much more expensive.
- At the menopause, the breast tissue will involute. During this process, much of the glandular tissue becomes fat, and the general density of the breast reduces.
- The average age of the menopause in UK women is 50.
Tumour confined to the ducts, or the acini of the lobules, and there is no infiltration of the basement membrane. Although described as non-invasive, these tumours have the potential to become invasive, and all invasive carcinomas will have at some time been non-invasive.
Non-invasive carcinomas therefore, are a stage of pre-malignancy, although not all non-invasive carcinomas will become malignant.
Ductal carcinoma in situ
- Occur in both premenopausal and post-menopausal women. Usually patients are 40-60 years of age. May be extensive, and associated with fibrosis, in which case it will be a large palpable mass.
- If large ducts are involved, it is associated with nipple discharge
- May present as Paget’s Disease of the nipple
- Accounts for 5% of breast cancers at presentation – often breast cancer presents in the invasive phase.
- Typically 10-100mm in diameter and unilateral/unifocal
- Histologically typically occur in small and medium sized ducts
- Lesions may have a solid centre, or a necrotic centre, which can subsequently calcify, making the lesions visible on mammography
- Spread locally along the ducts
- Have a risk of 30-50% of becoming invasive
- If completely excised, prognosis is excellent
Lobular carcinoma in situ
- Usually occur in pre-menopausal women
- Very difficult to detect – as it does not present as a lump, or cause many other signs.
- Often multifocal and bilateral
- No specific features on mammography
- 25-30% of cases will become invasive (i.e. malignant)
Invasive ductal carcinomas
- Account for 75% of all invasive carcinomas
- Occur in both pre and post menopausal women
Invasive lobular carcinoma
- Account for about 10% of invasive carcinomas
- Account for 2-3% of invasive carcinomas
- Their borders are not well defined, and they do not cause inversion of the nipple, or tethering of the skin.
- Better prognosis than invasive ductal or lobular carcinomas
- Cells arrange as tubules
- 1-2% of invasive carcinomas
- Account for a higher proportion of breast cancers detected at screening
- Prognosis is very good
- Usually large and well circumscribed
- Histologically show lymphocytic infiltrate and macrophages
- Better prognosis than for invasive ductal carcinomas
Local – directly into surrounding tissue
Via lymph nodes – in this case typically to the axillary and peri-clavicular nodes
- Sentinel node biopsy is a technique used to asses lymph node spread, without the need for dissection and biopsy of many nodes of the axilla. The sentinel node is the first axillary node along the lymphatic chain – thus all lymph from the breast will drain here first, before moving on through the lymphatic system. However, it is not an anatomical location, as the number and distribution of nodes varies between individuals. To identify the sentinel node a solution containing the radioactive isotope technithium and a blue dye is injected around the nipple/areolar and around the breast cancer itself. Then, a few hours later, the women undergoes surgery of the axilla, and using a hand-held Geiger counter-counter, and by looking which node has turned the deepest shade of blue(!) the surgeon can identify the sentinel lymph node. It removed and sent for histology. Sometimes several nodes may be removed if the spread of dye/isotope is more evenly spread between a few nodes.
Via the blood – to distant sites, in this case, the lungs and bones are most often affected. Other common sites include liver, brain and adrenal glands. The contralateral breast is also often a site of spread.
Unusual characteristics – breast cancers can recur as metastatic disease with / without local disease many years after the removal of the primary tumour. The reason why this occurs in unknown. It could be that the cancerous cells lie dormant, or that there is an alteration in the host immune system many years down the line that results in active disease.
- This can occur up to 20 years after removal of the primary tumour.
- Fine need aspiration (Cytology)
- Imaging (can be Mammography, MRI or USS)
- E1 – Normal (no lump)
- E2 – Benign lump
- E3 – A lump
- E4 – A suspicious lump
- E5 – Probable cancer
- C1: Inadequate
- C2: Benign
- C3: Atypia, probably benign
- C4: Atypia, probably malignant
- C5: Malignant
- R1: Normal
- R2: Benign
- R3: Indeterminate
- R4: Suspicious
- R5: Malignant
Staging and Prognosis
- Young age / premenopausal
- Large primary tumour size
- High grade tumour
- Oestrogen and progesterone receptor negative
- Positive lymph nodes
- About 50% of tumours have progesterone receptors
- Those with receptor positivity have a greater chance of survival due to treatment methods that can target this mechanism. The fact that the tumour is receptor positive also indicates a higher-level of cell differentiation – which for cancer generally is a good prognostic sign
- i.e. it hasn’t differentiated to an extent as to become unrecognisable.
- Small (<1cm tumour) with no spread – 90% survival
- Large, high-grade tumour. With >3 nodes involved – 20% survival
Tumour <20mm, no tethering or nipple retraction
No Nodal involvement
No distant metastasis
Tumour either: <20mm with tethering, or, 20-50mm
Axillary nodes involved but mobile
Tumour either <50mm with infiltration, ulceration or fixation, or, 50-100mm
Axillary nodes fixed
Tumour >100mm, or with ulceration and infiltration wide of the border of the primary tumour
Supraclavicular nodal involvement with/without oedema of the arm
- May be a wide local excision or mastectomy. Usually also involve reconstructive surgery.
- Axillary node sampling at the very least (e.g. sentinel node biopsy – above), but usually, axillary node clearance is performed.
- Local excision + radiotherapy – this gives equal survival to surgery, but the risk of recurrence is greater.
- Adjuvant radiotherapy – is given to the chest wall after mastectomy for tumours with a high risk of recurrence
- Radiotherapy to the axilla – is usually performed if there are +ve nodes on sampling, and node clearance was not performed.
- Side effects of radiotherapy to the chest wall / axilla:
- Rib fracture
- Brachial plexus injury
Suitable for all tumours with oestrogen and/or progesterone receptors. The growth of these tumours is prevented by tamoxifen.
Oestrogen receptor positive tumours
Treatment aims to decrease oestrogen activity
Tamoxifen is the agent of choice
- Given to all women with Oestrogen receptor positive disease for 5 years post op.
- Mechanism – binds to oestrogen receptors, preventing oestrogen from doing so, and resulting in a lack of DNA synthesis. It is non-steroidal. It causes the affected cell to remain in the G0 /G1 phases of the cell cycle.
- Tamoxifen is actually a pro-drug – and metabolised into its active agent endoxifen.
- Side effects
- Bone – the action of tamoxifen as an antagonist depends upon the target tissue. In bone, tamoxifen acts as an oestrogen agonist – and thus is protective against osteoporosis.
- Drugs whose oestrogen activity is dependent upon the target tissue are known as selective oestrogen receptor modulators (SERMs).
- Endometrium – the SERM activity on the endometrium is that of an oestrogen agonist – and as such, it increases the risk of endometrial cancer
- This is rare, although you should warn all women prescribed tamoxifen to be watchful of vaginal bleeding and report symptoms immediately.
- Cardiovascular – Slight increase on the risk of DVT, Increased risk of fatty liver
- CNS – Some evidence to suggest reduced cognition
- Reduced libido
- Newer than tamoxifen, and sometimes better tolerated. Again, only suitable for women with oestrogen receptor positive disease.
- Only suitable in post-menopausal women
- Mechanism – aromatase is an enzyme involved in oestrogen synthesis.
- In pre-menopausal women, the majority of oestrogen production occurs in the ovary
- In post-menopausal women, the majority of oestrogen production occurs in the adrenal gland, from the conversion of androgens. Oestrogen is also produced by adipose tissue.
- Aromatse inhibitors inhibit the conversion of androgens to oestrogen in the adrenals – and thus are only suitable as treatment for BC in post-menopausal women.
- Women with breast cancer with HER levels at 3+ in who have had chemotherapy (including anthracycline ± tamoxifen [if appropriate]
- Women with breast cancer who cannot tolerate anthracycline
- RACGP - The Red Book - Breast Cancer
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Breast Cancer - Patient.info
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.