Unit 1 - Screening and Imaging Flashcards
Why is it that non-melanoma skin cancers are often not included in cancer incidence and survival data?
This is because NMSC is the most common cause of the disease, accounting for around 20% of cases, yet the survival rates are incredibly high, usually, as the disease is detected early as tumours are often visible and subsequently it is responsible for a relatively low number of all cancer deaths (around 1%).
Discuss the way in which direct tumour cells can spread, using examples of different cancers, may cause issues for patients?
Direct spread, this is common in NMSC’s where there is no barrier to stop the tumour growing like bone or cartilage. This can generally be treated by either surgery or radiotherapy – however this ordeal way mean the patient suffers from anxiety, due to diagnosis or potentially that he may suffer from the disease again in the future or they may deal with self-confidence issues if the radiotherapy/Mohs Micrographic surgery leaves any potential damage to surrounding normal tissue – particularly if this is a visible area like the face.
Breast cancers also primarily spread directly before any lymphatic or haematological spread – these tumours can often become ulcerated as it will block the flow of blood/lymphatic vessels – preventing the wound from being healed.
Tumours can also spread via metastasis, this is via the lymph nodes or blood vessels, patients here are unlikely to undergo radical therapy, instead undergoing palliative therapy. What do these two terms mean?
Radical Therapy – focusses on preventing the tumour from growing to improve survival, rather than destroying the tumour.
Palliative therapy is not aimed to destroy the tumour or cure the cancer, but instead to relieve any symptoms or suffering the patient is experiencing.
Some tumours spread via lymph nodes, discuss how any lymph node spread is detected in a cancer of your choosing and explain what impact this has on the patient’s treatment.
Breast cancers primarily metastasise via the lymph nodes. Taking a sentinel lymph node biopsy can be used to determine if any spread has occurred. This is where a patient has Tc99m (radioactive) and a blue fluorescent dye injected near the tumour before surgery. The sentinel lymph node (the mostly likely to contain any tumour cells that have spread) is then identified based on the amount of gamma radiation and/or the fluorescence of the dye. This is then surgically removed and examined for any cancer cells. If there no are cancer cells present that treatment is likely to be local, but if these are cancer cells present treatment is likely required to be more aggressive and systemic.
Give examples of tumours that spread via blood vessels and transcoelomic spread?
Prostate cancer is often associated with haematological spread to the brain, pelvis and liver – the successful dissemination rate is relatively low due to stress during transport, however, this will likely lead to change in management from radical to palliative treatment.
Transcoelomic spread is when the tumour passes across a body cavity examples of this are the ovary to the peritoneum and the lung to the pleural space – this is because in these areas there is no barrier like cartilage or bone preventing tumour growth. Smaller micrometastasis here are known as peritoneal carcinomatosis.
Why is ‘cure’ a controversial word in cancer treatment and what terms are used instead to look at survival?
This is because the concept of curing/totally abolishing a cancer is incredibly rare at difficult as recurrence is very common – instead the aim is to reduce the risk of recurrence to as low as a value as possible – which is often coincided with the 5-year survival rates.
What are the 3 necessary components required for a screening system?
- The disease and its early manifestation must be known and well characterised (for a significant marker) with the early-stage treatment being associated with cheaper costs and better patient outcomes.
- The target population is identifiable and large enough for costs to be worthwhile (no point in some populations)e.g., age, gender, familial history etc
- The individual must have some personal risk if the condition is being screened for hence will commit to the process (give consent)
What are some potential problems patients might face during screening
- Anxiety relating to waiting for results or shock if results come back positive
- If the procedure is invasive or painful
- The threat of false negatives leading to unnecessary follow up treatments/screening associated with pain (as well as psychological effects and cost in general)!
- False negatives could put the patient at ease when they already have the disease and ignore any other symptoms of the disease
Because of some of these issues, the age of starting and how often the screening is used is datable (accuracy of tissue imaging and these other issues) – as well as cost as well, given that most of these programmes and subsequent treatment is funded in the UK by the NHS which is government funded.
What 10 Criteria do the WHO required for a screening programme to be considered beneficial?
I. The condition is an important health problem
II. Its natural history is well understood
III. It is recognisable at an early stage
IV. Treatment is better at an early stage
V. A suitable test exists
VI. An acceptable test exists
VII. Adequate facilities exist to cope with abnormalities detected
VIII. Screening is done at repeated intervals when the onset is insidious
IX. The chance of harm is less than the chance of benefit
X. The cost is balanced against benefit
Can be summarised into Easily identifiable, curable, and common (although cervical cancer is not common but is screened for).
What three factors must the screen itself be?
- Not too unpleasant/painful/distasteful
- Cheap
- Accurate (sensitivity and specificity)
Discuss some disadvantages of cancer screening?
- False negatives – a patient who has the disease, but the test comes back negative – symptoms could be ignored leading to disease progression and poorer prognosis – this may also put people close to that person less likely to be screened themselves due to lack of trust
- False positives – Where a patient does not have the disease but has a positive result – could lead to unwarranted stress and could be traumatic invasive testing and may make them less likely to undergo further screening tests in the future (distrust)
- Interval disease – Where breast cancer may occur between screening events – could become a shock to patients
- Compliance – will patients continue to come in subsequent screens or will they feel they are okay given the previous negative results (Education and advertisement campaigns as seen with prostate cancer in football league.
- Cost- these services must be cost effective by reducing the potential cost of subsequent treatment
- Person to patient – Some people may fear turning up in case of getting a positive result – that sudden transformation can be quite a shock to individuals
What Cancer Screening programmes are currently used in the UK?
Breast cancer
Helps identify those with either carcinoma in situ or stage T1, which can be removed quite easily using surgery. This consists of a two-view mography (X-rays in lateral-medial and top-bottom). In 50–70-year-olds, Some countries use a different age cut-off, but in those younger than 40 the exposure to radiation is actually associated with increased development of cancer. Additionally, for every death prevented 2-3 cancers will be over diagnosed - Only a proportion of Tis will develop into invasive breast cancer – but at this moment there is no way to identify who these patients are – overtreatment.
Despite this, it can be associated with discomfort as well as radiation hazards. Additionally, due to the ‘taboo’ nature of breasts, this could be a difficult process for some patients.
Cervical Cancer
Despite not being a common disease, cervical cancer is one of the only cancers screened for. Despite dramatically improving survival rates – compliance is quite low at only around 70% - which is dropping over time – this can be due to embarrassment, over-confidence due to lack of symptoms and worried about the procedure or possible results – because of this campaigns like smear for smear are helping educate young people and encourage them to comply.
CRC
This used a high sensitivity faecal occult blood test looking for blood – but this can often put off patients – if the disease can be diagnosed early then the disease is very curable – but because symptoms don’t become apparent until late in disease. Because of this, compliance is only at around 65% - which needs to be increased to around 80% if it is to be effective!!
There are some issues as in some cases false positives can be caused by other problems like ulcers or polyps – hence a colonoscopy is required as a validatory follow up.
Discuss why despite prostate and ovarian cancer being very common in the UK do not have a screening programme?
Prostate cancer can be either be indolent or aggressive, with those with the indolent disease often living with the disease rather than dying with it – hence this population would gain no benefit from this, whilst having to deal with anxiety related to diagnosis unnecessarily. But as PSA-test is offered if the patients wish to have one.
- It is a significant issue and one of the biggest causes of cancer death
- The impact on patients is variable, in some cases the disease is indolent requiring minimal intervention
- Is recognisable at an early stage
- Indolent – unnecessary, active surveillance better, repeat PSA
- Isn’t specific in prostate cancer, benign hyperplasia
- ^ this is common in older patients
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- Screening when it is done early can increase patient survival rates IN SOME CASES (indolent)
- Overdiagnosis, stress caused with diagnosis with limited impact of cancer itself on patient health.
- Expensive, especially in an ageing population
Ovarian cancer screening was trialed using either ultrasound or CA-125 levels, but due to false positives (Can be used by other conditions like endometriosis) it was decided that it wasn’t financially beneficial or significantly improved patient survival.
List the five generally types of imaging used in cancer with a brief description
- Plain/Contrast agent Radiography – used X-rays to detect bone fractures and mammography with high energy photons used to look at density of tissue. Not so good for soft tissue. Generally, 1st used and can help identify what other modalities should be used next!
- Computed Tomography – Great anatomical detail and can be enhanced using contrast agents -> used in radiotherapy planning.
- Magnetic resonance imaging – Great anatomic detail (especially in head/neck) – often used with CT in radiotherapy
- Radionuclide imaging (like PET) – gives physiological activity but poor anatomical information as images are hard to interpret
- Ultrasound – great anatomical detail for soft tissues like pelvic soft tissue
What is image registration and give an example?
Imagine registration is where different imaging modalities are used in combination and aligned/overlayed to improve our knowledge/understanding of the patients situation, as each will have their own advantages/disadvantages. This can include using radionuclide (PET) alongside CT to combine both the anatomical and physiological information. CT and MRI can be used together to improve anatomical information and minimise any off-target effects in radiotherapy!
Why is image registration so important in cancer?
Joins anatomical and physiological information so can be used for:
- Follow up-studies
- Detection
- Staging of the disease (will affect treatment)
- Radiotherapy planning – different imaging techniques will identify different target areas to minimise off-target effects of treatment even using MRI and CT
Why might overlaying images sometimes not be enough?
There might be differences in patient position or the magnification of images
What does NICE stand for?
National institute for health and clinical excellence
What are guidelines and what is their purpose in radiology? (IREFER)
A set of statements to assist the practitioner and patients about healthcare options in specific circumstances – which is evidence based and constantly updated!
- To determine the most appropriate imaging examination
- Reduce the number of unnecessary referrals and radiation dose
- Overall improving clinical efficiency
- Based on research
What questions should a radiologist ask before imaging has been carried out?
- Has the investigation been done before?
- Do you need to image the patient now?
- What will the results mean to changes in patient management (should be a change otherwise pointless)?
- What is the most appropriate technique?
- What information is given from the referrer? Is there enough information to suggest the correct examination is taken place