Week 7 - TB and Lung Cancer Flashcards
1
Q
Describe a primary TB infection
A
- Occurs on first exposure
- Primary focus = development of sub-pleural focus of tubercles following deposition of TB bacilli in the alveoli
- TB bacilli drain from the primary focus into the hilar lymph nodes
- Primary focus + draining hilar lymph nodes = primary complex
- Primary complex does not heal, but continues to progress and causes disease
- Most infections resolve with local scarring
- Most primary infections will heal with or without calcification of the primary complex
2
Q
Describe a post-primary TB infection
A
- Development of TB beyond the first few weeks
- Infection may progress throughout the body (Miliary spread)
- – May resolve spontaneously or develop into localised infection
- Due to reactivation of latent TB
3
Q
Describe latent TB infection
A
- In the majority of cases, before healing occurs in primary infection, some TB bacilli enter the blood stream
- Haematogenous spread occurs, resulting in the seeding of tubercle bacilli to other parts of the lung as well as other organs (extra-pulmonary sites)
- With the development of cell-mediated immunity the infection is contained
- Primary complex heals, but a small number of organisms remain viable in the lungs/other organs, such as:
- – Larynx
- – Lymph nodes
- – Pleura
- – Brain
- – Kidneys
- – Bones and joints
- This state, where TB bacilli can persist within the human host, without causing disease, for years or until death due to other causes, is known as latent TB
- The person remains well, but the potential for reactivation at any site is always present
- – Reactivation usually occurs when the patient’s immune mechanisms wane or fail
- Characterised by a positive tuberculin skin test
- – Demonstrates a type IV hypersensitivity reaction to proteins derived from mycobacteria
4
Q
Describe the host response to TB infection
A
- Mycobacterium TB is ingested by macrophages
- It escapes from the phagolysosome to multiply in the cytoplasm
- At the same time it provokes an immune response, stimulating the release of of IL-12
- – This in turn drives the release of IFN-γ and TNF-α from NK and CD4 cells
- – These cytokines activate and recruit more macrophages to the site of infection, resulting in the formation of granulomas
5
Q
What are the primary changes in TB?
A
- Few symptoms
- Lymph nodes may become enlarged in young people
6
Q
What are the post-primary changes in TB?
A
Classical presentation:
- Cough
- Fevers
- Weight loss and general debility
7
Q
How do you diagnose TB?
A
- Usually suggested by findings of compatible x-ray changes during investigation of patients with:
— Persistent cough
— Haemoptysis
— Unresolved pneumonia
— Nonspecific symptoms
• E.g. fever, weight loss - Plus the identification of the tubercle bacillus in the appropriate body fluid by direct smear and subsequent culture
— Important to isolate the organism and determine its susceptibility to drugs
8
Q
What is the classical presentation of TB?
A
- Cough – not always productive
- Often with fevers towards the end of the day
- Weight loss and general debility
9
Q
What would you expect to see on a chest x-ray for TB?
A
- Shadowing
- Cavities
- Consolidation
- Calcification
- Cardiomegaly
- Miliary seeds
10
Q
What are some symptoms and signs of TB?
A
Symptoms: - Fever - Night sweats - Weight loss and anorexia - Tiredness and malaise - Cough - Haemoptysis occasionally - Breathlessness if pleural effusion Signs: - Non-specific --- Fever --- Weight loss - Often no chest signs, despite a chest x-ray abnormality - Maybe crackles in affected area - In extensive disease: --- Signs of cavitation --- Fibrosis - If pleural involvement, there are typical signs of effusion
11
Q
Describe pleural TB
A
- More common in males, there are 2 mechanisms of pleural involvement
- There is almost always some pulmonary disease present:
— Hypersensitivity response in primary infection
— TB empyema with ruptured cavity
• Has a tendency to burrow through the chest wall
12
Q
Describe lymph node TB
A
- More common in children, women and Asians
- It is often painless and occurs most commonly in the neck
13
Q
Describe osteo-articular disease
A
TB burrows into bone
- Tuberculous spondylitis
- – Most common form of osteoarticular TB
- – Starts in sub-chondral bone and spread to vertebral bodies and joint space, before following the longitudinal ligaments, anterior and posterior to the spine
- – Mainly occurs in the lower thoracic and lumbar spine, but can be very high
- – Paraplegia and quadriplegia occurs in 25% of cases
- Poncet’s disease:
- – Aseptic polyarthritis
- – Knees, ankles and elbows
14
Q
Describe miliary TB
A
- Bacilli spreading through the bloodstream
- Either during primary infection or as reactivation
- Lungs are always involved
- – Even spread throughout both lungs, as it is in the blood
- – Many visible through the lungs on an X-ray
- Headaches suggest meningeal involvement
- Few respiratory symptoms
- Ascites may be present
- Retinal involvement in children
15
Q
How do you manage TB?
A
- Multi-drug therapy for 2 months:
- – Rifampicin
- – Isoniazid
- – Pyrazinamide
- – Ethambutol
- After 2 months, 2 of them are dropped
- – RIfampicin and isoniazid are continued for another 4 months
- Multiple drugs are used in an attempt to combat resistance
- Vitamin D
- Surgery
- – Rare
- Can be problems with compliance since there are lots of different pills to take for quite a long time
- – Can monitor it
- Need to do a follow up culture
16
Q
What is the role of the BCG vaccine?
A
- A vaccination against tuberculosis
- Prepared from a strain of the Attenuated Live Bovine TB bacillus
- The vaccine has a variable efficacy
- – Depends on the genetic variation of populations and BCG strains
- – Only lasts 15 years at most
- In the UK, it is only given to high-risk groups
17
Q
What are some high risk groups for TB?
A
- HIV
- Silicosis
- Malnutrition
- Overcrowding
- – Prisons, homeless shelters
- IV drug abusers
- Chronic lung disease (smokers)
- Ethnicity
- – Asians more likely
- Diabetes
- Corticosteroids/anti α-TNF antibody
18
Q
What happens (in public health terms) if a case of TB is suspected?
A
- If TB is suspected, contact is immediately made with TB radiology
- The patient goes straight into a TB clinic, with no waiting times
- – Given a questionnaire
- – Sputum samples are taken
- Treatment begins within 7 days
19
Q
Describe the incidence of lung cancer
A
- Males:
- – Most common male cancer
- – Mortality rate is around 100 per 100,000
- – Incidence slowly falling due to reduction in smoking
- Females:
- – Exceeds breast cancer as a cause of death in women
- – Mortality rate is around 40 per 100,000
- – Incidence is steadily rising
- Socio-economic groups:
- – Wide variation
- – Rate 3 times high in lowest SE group compared with highest
20
Q
What are the risk factors for lung cancer?
A
- Smoking (main risk factor)
- – Risk is proportional to the duration of habit and the number of cigarettes smoked
- Asbestos
- Radon
- Other “occupational carcinogens”
- – Chromium, nickel, arsenic
- Genetic/familial factors
21
Q
What are some symptoms of a primary lung tumour?
A
- Cough
- Dyspnoea
- Wheezing
- Haemoptysis
- Lung infection
- Chest/shoulder pain
- Weight loss
- Lethargy/malaise
22
Q
What are some symptoms of regional metastases in lung cancer?
A
- Bloated face
- Hoarseness
- Dyspnoea
- Dysphagia
- Chest pain
23
Q
What are some symptoms of distant metastases in lung cancer?
A
- Bone pain/fractures
- CNS symptoms
- – Headache
- – Double vision
- – Confusion
- – Etc.
24
Q
What is paraneoplastic symptoms?
A
The presence of a symptom or disease due to the presence of cancer in the body, but not due to the local presence of cancer cells
- Mediated by humoral factors (cytokines and hormones) secreted by tumour cells, or the immune response against tumour cells
25
Q
What imaging techniques would you use to diagnose or stage cancer?
A
- First clinical suspicion = chest x-ray
- Diagnosis and staging =
- – Staging chest CT
- – PET scan
- – Isotope bone scan
26
Q
What are the different types of lung cancer?
A
- Non-small cell:
- – Squamous cell carcinoma
- – Adenocarcinoma
- – Large cell carcinoma
- Small cell carcinoma:
- Rare tumours
27
Q
What does the prognosis of lung cancer depend on?
A
- Cell type
- – Small cell is worse than non-small cell
- Stage of disease
- Performance status
- Biochemical markers
- Co-morbidities
- – E.g. cardiac or chronic respiratory disease
28
Q
What are the different treatments for lung cancer?
A
- Surgery
— Mostly for non-small cell
— Best chance for cure - Radiotherapy
— Radical – with curative intent
— Palliative – for symptom control - Combination chemotherapy
— Small cell – potentially curative in a minority
— Non-small cell - modest survival increase, symptom control - Combination therapy
— Combination chemo-radiotherapy – potentially curative - Biological therapies
— Based on mutational analysis - Palliative care
— Active symptom control, e.g.:
• Analgesia
• Radiotherapy
• Airway stents
29
Q
How do you manage non-small cell cancer?
A
- Palliative radiotherapy for local symptoms
- Chemotherapy
- Combination therapy
- Targeted agents
30
Q
How do you manage small cell cancer?
A
- Rarely operable
- Combination therapy
- Palliative chemotherapy
- – For symptoms
- Death from cerebral metastases common
