Prevention of cancer
Consultant Palliative Medicine Northern Ireland Hospice, Belfast, UK
E-mail: alimaxuk{at}yahoo.com
 |
Abstract |
|---|
 TOP Abstract The GP curriculum and...Primary prevention strategiesSecondary preventionCervical cancer screeningBreast cancer screeningColorectal cancer screeningReferences |
|---|
In 2005 in the UK, there were 153 491 deaths from cancer—one in four of all deaths (29% of male and 24% of female deaths). Seventy-six percent of these deaths occur in people aged over 65. Death rates rise with increasing age. However, cancer causes a greater proportion of deaths in younger people, with cancer being responsible for 37% of deaths in those under 65 (47% of deaths of women; 31% of deaths of men). Lung cancer is the most common cause of cancer death in both men and women (Fig. 1).
Cancer is not caused by one factor but is multi-factorial. Causes include:
- Lifestyle exposures, such as obesity, alcohol, smoking and viruses
- Environmental exposures, such as asbestos, azo dyes, radiation exposure
- Inherited genetic susceptibility, such as BRCA1 and two genes (account for 2–5% of all breast cancers).
‘Primary prevention’ aims to modify factors that promote or protect against carcinogenesis. ‘Secondary prevention’ aims to detect pre-malignant disease or early malignant disease at a stage when it is still curable.
GPs have a crucial role to play in promoting health and preventing disease. Cancer is a clear concern for many patients who consult their doctor and it is a concern driven by common life experience. The role of the GP extends from primary prevention of cancer through early diagnosis to terminal care. Curriculum statement 12 ‘Care of People with Cancer and Palliative Care’, statement 5 ‘Healthy People’ and statement 6 ‘Genetics in Primary Care’ are relevant to the prevention of cancer. Individual cancers are also covered in the relevant topic statements (for example bowel cancer screening is mentioned in statement 15.2 ‘Digestive problems’). In relation to cancer prevention, a GP should be able to:
|
|
Primary prevention strategies |
|---|
|
TOPAbstractThe GP curriculum and...Primary prevention strategiesSecondary preventionCervical cancer screeningBreast cancer screeningColorectal cancer screeningReferences |
|---|
Dietary modification
There is a substantial body of evidence that links diet to cancer risk. Obesity is associated with increased risk of breast, endometrial, colorectal and renal cancers. Colorectal cancer is more common in populations having a low fibre diet, and some food additives are known carcinogens and have been banned from use. On the other side, there is some evidence that diets rich in antioxidants may reduce cancer risk.
Smoking cessation
Cigarette smoking has been identified as the most important cause of preventable death in the UK with one out of three deaths from cancer and 88% of all lung cancer deaths being linked to smoking. Smoking is associated with increased rates of lung, lip and other mouth and throat cancers, stomach, colon and bladder cancer. Smoking cessation reduces risk of cancer.
Alcohol reduction
Excess alcohol intake is particularly associated with liver cancer and oropharyngeal cancers. It is also associated with breast cancer and oesophageal cancer.
Awareness and avoidance of occupational carcinogens
Mesothelioma can follow even light exposure to asbestos. There is a long time lag of 20–40 years between exposure and disease but the mean time to death following diagnosis is just 2 years. Workers exposed to asbestos also have increased risk of adenocarcinoma of the lung, particularly smokers who have five times the increased risk of non-smokers. Other cancers associated with occupation include:
- Woodworkers—nasal cancer
- PVC manufacturers—liver cancer
- Nickel refiners—lung and nasal cancer
- Azo dye manufacturers—bladder cancer
Reducing sun exposure
Sun exposure is a major risk factor to basal and squamous cell skin cancer, and malignant melanoma. Risk of skin cancer can be reduced by adhering to the sun safety code (Box 1).
Box 1. Prevention of skin cancer: The sun safety code:
Information for patients on preventing sunburn
|
Vaccinating against virus-related cancers
Several viral infections are known to cause cancer. These include:
- Hepatitis B and C—associated with liver cancer
- Human immunodeficiency virus (HIV)—associated with Kaposi's sarcoma and lymphoma
- Epstein-Barr virus—associated with Burkitt's lymphoma, nasopharyngeal carcinoma and lymphoma
- Human papilloma virus (HPV)—associated with cervical cancer.
Avoiding high-risk sexual activity
Avoidance of high-risk sexual activity reduces the risk of HPV infection, Hepatitis B infection and HIV infection (see above).
Surgical prevention
Certain cancers associated with congential or genetic abnormalities (such as undescended testes, familial adenomatous polyposis (FAP), ulcerative colitis, hereditary colorectal cancer, ovarian cancer or breast cancer) may be prevented by prophylactic surgery.
Genetic screening
In 2003, The Human Genome Project revealed the DNA sequence for 30 000 genes. Despite these advances, the impact of lifestyle and environmental factors, which lead to genetic mutations, make determining an individual's risk of cancer from a ‘genetic blueprint’ extremely difficult. However, genes predicting some forms of cancer have been identified—particularly genes predicting breast and ovarian cancer. Trials of primary prevention for women at high genetic risk of breast or ovarian cancer are underway. Consider referral if there is a high genetic risk of breast, ovarian or bowel cancer.
|
Secondary prevention |
|---|
|
TOPAbstractThe GP curriculum and...Primary prevention strategiesSecondary preventionCervical cancer screeningBreast cancer screeningColorectal cancer screeningReferences |
|---|
The idea of cancer screening is attractive—the ability to diagnose and treat a potentially serious condition at an early stage when it is still treatable. An ideal screening test should pick up all those who have the disease (have high sensitivity) and must exclude those who do not (high specificity). It must detect only those who have a disease (high positive predictive value) and should exclude only those who do not have the disease (high negative predictive value) (Table 1).
|
The World Health Organization recommends that screening should only be introduced to the target population if the following (Wilson-Jungner) criteria are met:
- The condition being screened for is an important health problem
- The natural history of the condition is well understood
- There is a detectable early stage
- Treatment at early stage is of more benefit than at late stage
- There is a suitable test to detect early stage disease
- The test is acceptable to the target population
- Intervals for repeating the test have been determined
- Adequate health service provision has been made for the extra clinical workload resulting from screening
- Risks, both physical and psychological, are less than the benefits of screening
- The costs of screening are worthwhile in relation to the benefits gained
|
There is ‘no’ ideal screening test. For any screening test, always explain:
|
|
Cervical cancer screening |
|---|
|
TOPAbstractThe GP curriculum and...Primary prevention strategiesSecondary preventionCervical cancer screeningBreast cancer screeningColorectal cancer screeningReferences |
|---|
Screening prevents 1000–4000 deaths per year in the UK from squamous cell cancer of the cervix (Fig. 2). Cervical cancer almost exclusively occurs in women who are or have been sexually active.
|
|
The screening test
A smear test is routinely offered to all women age between 25 and 64 years who are sexually active. There is no upper age limit for the first smear. Frequency of screening depends on age:
|
In the UK, the traditional Papanicolou smear (Pap smear) used for cervical screening is being replaced by liquid-based cytology. The sample is collected in a similar way to the Pap smear but, rather than smearing the sample from the spatula onto a slide, the head of the spatula, where the cells are lodged, is broken off into a small glass vial containing preservative fluid or rinsed directly into the preservative fluid. This method of cell collection reduces the number of inadequate smears taken, as cervical cells can be examined even if the sample is contaminated with blood, pus or mucus.
Ideally, smears should be taken mid-cycle. Avoid menstruation if possible but note on the form that the patient is menstruating if taking the smear during menstruation is unavoidable. Routine bimanual examination is unnecessary. Only do a pelvic examination if clinically indicated (for example painful or heavy periods).
It is important to have adequate training to take smears. Poor smear taking misses 20% of abnormalities. Courses are available and skills should be updated every 3 years.
Practices undertaking cervical screening can gain Quality and Outcome Framework points through their cervical screening programmes (Table 3). Practices must:
- Provide information to eligible women to allow them to make an informed decision about taking part in the programme. Include in this information about the test, the condition being sought, the possible results of screening and their implications.
- Ensure that staff are properly trained and equipped to perform the test and perform the cervical screening test.
- Arrange for women to be informed about the results of their tests.
- Ensure that results are followed up appropriately (Table 4).
- Maintain records of tests carried out, results and any clinical follow up requirements.
|
|
|
The role of human papilloma virus testing
Infection with HPV 16, 18, 31 and 33 is associated with cervical intra-epithelial neoplasia and cervical cancer, 99.7% of cervical cancers contain HPV DNA and women with HPV infection are 70 times more likely to develop high-grade cervical abnormalities. A pilot of HPV testing is being conducted within the UK cervical screening programme. Women with borderline or mild dyskaryosis are tested for high-risk HPV using the sample collected for cytology. If HPV is found, the woman is referred to colposcopy; if HPV is not found, the woman is invited for a repeat smear and further HPV test after 6 months.
|
Breast cancer screening |
|---|
|
TOPAbstractThe GP curriculum and...Primary prevention strategiesSecondary preventionCervical cancer screeningBreast cancer screeningColorectal cancer screeningReferences |
|---|
In the UK, there has been a national screening programme for breast cancer since 1988. The aim of the programme is to detect breast cancer at an early stage in order to increase survival chances (Fig. 3). Statistics show that although breast cancer diagnosis is increasing, mortality has decreased since screening has been introduced (Fig. 4).
|
|
The screening test
Two-view mammographic screening for breast cancer is available every 3 years to women aged between 50 and 70 years. Older women can also request screening every 3 years but will not be automatically called. The organization of breast cancer screening in the UK is summarized in Fig. 5.
|
Screening detects 85% of cancers in women aged over 50, 60% of which are impalpable and 70–80% of screening-detected cancers have good prognosis. Cancer occurring in the interval between screens (interval cancer) can occur through failure to detect a cancer at screening or as a result of a new event after screening took place. In the first year after screening, 20% of breast cancers are interval cancers. This increases to around 60% in the third year. Reducing the screening interval to less than 3 years does not reduce mortality.
GPs have an important role in encouraging women to attend breast screening. Sending personalized invitations for screening to women from their GPs increases uptake rates. Eighty-one percent of women find mammography uncomfortable, but 90% return for subsequent screens. False-positive results as a result of screening cause anxiety as well as prompting further invasive investigations. Anxiety levels in women recalled and then found to be disease-free are higher in the year after the recall appointment, than in women who receive negative results at screening.
Women with family history of breast cancer
Women at raised risk of breast cancer who are under 50 years of age should be referred for annual two-view mammography between the ages of 40 and 49 years. In addition, high-risk women of under 50 years may benefit from genetic screening and/or magnetic resonance imaging (MRI) screening:
- Refer for genetic screening if breast cancer genes have been identified in the family
- Refer to secondary care if the woman has one or more high-risk criteria (Table 5)
- Refer to secondary care if the woman is aged 40–49 years and has one or more moderate-risk criteria (Table 5).
|
Women known to have a genetic mutation should be offered annual MRI from 20 years of age if they have the TP53 mutation, or from 30 years of age if they carry the BRCA1 or 2 mutation. MRI surveillance should also be offered to women aged 30–39 years with a 10-year risk of breast cancer in excess of 8%, to those aged 40–49 years with a 10-year risk of breast cancer in excess of 20% and to women with increased risk of breast cancer aged 40–49 years who have a dense breast pattern on mammography. Percentage risk of breast cancer is determined by specialist assessment.
|
Colorectal cancer screening |
|---|
|
TOPAbstractThe GP curriculum and...Primary prevention strategiesSecondary preventionCervical cancer screeningBreast cancer screeningColorectal cancer screeningReferences |
|---|
Screening for colorectal cancer will be available throughout the UK by 2009. More than 90% of patients presenting with tumour confined to the bowel wall have long-term survival. However, without screening, most tumours are detected at advanced stages and overall 5-year survival is only 40%. The aim of the programme is to detect colorectal cancer at an early stage to increase survival chances. If 60% of those aged between 60 and 69 are screened, 1200 deaths will be prevented each year.
The screening test
Faecal occult blood testing kits are sent every 2 years to all patients aged 60–69 years with instructions for completion at home and return. Patients over 70 years may also request testing kits. The test kit has three flaps, each with two windows underneath. Two samples are taken from a bowel motion and spread onto the two windows under the first flap using the cardboard sticks provided. The flap is then sealed and the process repeated using the remaining two flaps for the subsequent two bowel motions. Once all six windows have been used, the kit is returned. Kits must be returned within 2 weeks of the first sample being taken. A result is then sent to the patient within 2 weeks.
Possible outcomes are summarized in Table 6. It is estimated that 72% of those tested will be referred on for colonoscopy. Possible colonoscopic outcomes and the resulting action taken are summarized in Table 7.
|
Family history of colorectal cancer
If a patient has one first-degree relative (mother, father, sister, brother, daughter or son) with colorectal cancer, his or her risk of developing colorectal cancer is increased two to three times. Refer for colonoscopy at presentation or aged 35–40 years (whichever is later) and repeat colonoscopy aged 55 years if the patient has:
- Two first-degree relatives with a history of colorectal cancer or
- One first-degree relative with a history of colorectal cancer aged under 45 years.
Refer for specialist follow-up and genetic counselling if:
- More than two first-degree relatives with a history of colorectal cancer or
- Family history of:
- FAP
- Juvenile polyposis
- Peutz-Jehger's syndrome
- FAP
- Hereditary non-polyposis colorectal cancer
- MMR oncogene
Ulcerative colitis
Patients with ulcerative colitis have increased risk of colorectal cancer. Offer all patients a follow up plan agreed with their specialist. In some cases, prophylactic colectomy is appropriate.
Previous colorectal cancer
Patients with a history of previous colorectal cancer are at increased risk of developing a second colorectal primary. After successful treatment, younger patients are routinely followed up with colonoscopy every 5 years until the age of 70. In primary care, even if secondary care monitoring is in progress, remain vigilant for recurrences and re-refer urgently if suspected.
Key points
|
| Questions frequently asked by patients about cervical screening Should I have cervical screening if I’m pregnant or trying to get pregnant?
Ideally, women should not have cervical screening when pregnant or possibly pregnant. However, this will depend on your own individual circumstances. If you have had abnormal smears in the past, for example, or if you have not accepted your past invitations for screening, then you should consult your doctor or practice nurse to ask for advice. If you have a normal smear history, then it is better to wait until When is the best time in the menstrual cycle to have cervical screening? Mid-cycle (usually between 10 and 16 days after your last period) is the best time because a clearer sample can be obtained around this time. But it is not a strict rule, so do take advice from your doctor or practice nurse if you cannot make an appointment at that time. Will cervical screening pick up any other infections? It might, but that is not really the aim of the programme which is to detect and treat early abnormalities which, if left untreated, could lead to cervical cancer. Incidental findings of infections may be reported. Your doctor will then act on them as needed. I’ve had a hysterectomy—do I still need cervical screening? If your cervix is still present after your hysterectomy, then you will still need cervical smears. Sometimes, another sort of smear (a vault smear) is needed after hysterectomy even if you do not have a cervix. Normally, if you do not have a cervix, then you do not need cervical screening. The surgical team who performed the operation will decide on what kind of follow-up is appropriate. My cervical screening test showed borderline changes. Why do I have to wait 6 months for a repeat test—won’t they get worse? The reason we repeat the test in 6 months is to give minor changes a chance to get better without any treatment, which is what usually happens. If the repeat test is normal, you will be asked to have two more tests in 6 and 12 months’ time to check that the cells are still healthy. You can then go back to receiving routine invitations as before. If your repeat test still shows borderline changes (also called mild dyskaryosis), you may be referred for a colposcopy.
Further information for women
|
3 months after the delivery before you go for cervical screening.
| Questions about bowel cancer screening frequently asked by patients What is the purpose of bowel cancer screening? Bowel cancer screening aims to detect cancer of the colon or rectum at an early stage, before there are any symptoms, when treatment is more likely to be effective. Is screening for bowel cancer important? About 1 in 20 people in the UK will develop colorectal cancer during their lifetime. It is the third most common cancer in the UK and causes 16 000 deaths each year in the UK. Regular screening has been shown to reduce the risk of dying from colorectal cancer by 16%. What does the NHS Bowel Cancer Screening Programme do? It offers screening every 2 years to all men and women between the ages of 60 and 69 in the UK. Invitations are automatically sent to everyone in this age group and a screening kit is sent so that they can do the test at home. The test involves taking a small amount of your bowel motion and putting it on a card. Although some might find this test unpleasant, it can be done in the privacy of your own home. If you are aged 70 or over, you can ask for a screening kit by calling freephone number: 0800 707 60 60 What happens if I have an abnormal result? Depending on the result of your test, you may be asked to repeat the test, and/or be referred for a colonoscopy. A colonoscopy is an investigation that involves looking at your bowel directly with an endoscope. Most people who are offered colonoscopy will not have cancer, but in the unlikely event that colonoscopy shows that you do have bowel cancer, you will be referred immediately for specialist treatment. If bowel cancer is picked up at the earliest stage, you have a 90% chance of survival. Does screening pick up all colorectal cancers? No test is 100% accurate. There is a small possibility that you can have a negative screening test and still have bowel cancer. Stay alert to symptoms of bowel cancer and see your GP if you are worried. Symptoms to look out for are:
Further information for patients Frequently asked questions are reproduced with permission in modified format from website: http://www.cancerscreening.org.uk
|
| Questions frequently asked by patients about breast cancer screening I haven’t been called for breast screening even though I’m over 50 - do I need to contact anyone? The NHS Breast Screening Programme is a rolling one which calls women from doctors’ practices in turn. This means that not every woman receives her invitation as soon as she is 50. It will be some time between the ages of 49 and 52. If you are registered with a GP and the practice has your correct details, then you will automatically receive an invitation. You do not need to contact anyone but you might like to check your surgery has your correct contact details and ask them when the women on their list are next due for screening. I’m worried that I might have breast cancer. Can I walk into the mobile breast screening unit and request a mammogram? The NHS Breast Screening Programme is a population screening programme which invites all women aged 50–70 as a matter of routine. It is not aimed at women who already have symptoms. So if you have found something that worries you or are concerned about your breast health, you should see your GP in the usual way. He or she will decide whether or not you need to be referred for further investigations or treatment. Why doesn’t the NHS screen younger women? Mammograms are not as effective in younger women because the density of the breast tissue makes it more difficult to detect problems and also because the incidence of breast cancer is lower. The average age of the menopause in the UK is 50 and so this is the age when women join the NHS Breast Screening Programme. As women go past the menopause, the glandular tissue in their breast reduces and the breast tissue is increasingly made up of only fat. This is clearer on the mammogram and makes interpretation more reliable. Why does breast screening stop at 70? It does not. Although women over 70 are not routinely invited for breast screening, they are encouraged to call the local unit to request breast screening every 3 years. Cards have been produced to help them remember and these are handed out at their last routine breast screening appointment. Women abroad get more frequent breast screening. Why doesn’t this happen in the UK? A large research trial in 2002 concluded that the NHS Breast Screening Programme has got the interval between screening and invitations about right at 3 years, compared with more frequent screening.
Further information for women Over 70? You are still entitled to breast screening—available from website: http://www.cancerscreening.org.uk
|
|
References |
|---|
|
TOPAbstractThe GP curriculum and...Primary prevention strategiesSecondary preventionCervical cancer screeningBreast cancer screeningColorectal cancer screeningReferences |
|---|
-
Bandolier Cancer. Available from: www.jr2.ox.ac.uk/bandolier/booth/booths/cancer.html [date last accessed 6.12.2007].
Cancer Research UK Cancer statistics. Available from: info.cancerresearchuk.org/cancerstats/ [date last accessed 6.12.2007].
Classification and care of women at high risk of familial breast cancer in primary, secondary and tertiary care. (2006) Available from: www.nice.org.uk/guidance/index.jsp?action=byID&;o=10994 [date last accessed 6.12.2007].
National Electronic Library for Screening. Available from: www.library.nhs.uk/screening [date last accessed 6.12.2007].
NHS Cancer Screening Programme. Available from: www.cancerscreening.org.uk/ [date last accessed 6.12.2007].
NICE. Oxford GP Library: Cancer Care (In press). Oxford: Oxford University Press.
Referral guidelines for suspected cancer. (2005) Available from: www.nice.org.uk/guidance/index.jsp?action=byID&;r=true&o=10968 [date last accessed 6.12.2007].
Watson M, Fenton A, Drake A, McLoughlin C, Simon C. Oxford GP Library: Cancer Care (In press). Oxford: Oxford University Press.
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||