Asbestos-related lung disease (incl. asbestosis and mesothelioma)

Question 1

What is asbestos-related lung disease?

Answer 1

disorders of the lung and pleura caused by the inhalation of asbestos fibres.

Asbestos-related diseases include:

non-malignant disorders such as:

• asbestosis (pulmonary fibrosis due to asbestos)
• diffuse pleural thickening
• pleural plaques
• pleural effusion
• rounded atelectasis

malignancies such as:

• lung cancer
• malignant mesothelioma

Question 2

What is asbestosis?

Answer 2

diffuse interstitial fibrosis of the lung as a consequence of exposure to asbestos fibres.

Pleural abnormalities, which are also caused by the inhalation of asbestos fibres, include:

• plaques that may or may not be calcified
• diffuse pleural thickening
• benign pleural effusions
• rounded atelectasis.

These pleural abnormalities may occur either in concordance with or in the absence of parenchymal fibrosis

Question 3

What is the aetiology of asbestosis?

Answer 3

inhalation of asbestos fibres.

(asbestos = fibrous silicate)

Question 4

Name some risk factors for asbestosis

Answer 4

• cumulative dose of inhaled asbestos (maintenance & repair workers)
• smoking
  
  • inhibits ability of lung to clear asbestos fibres
  • is not associated with pleural changes

Question 5

Summarise the epidemiology of asbestosis

Answer 5

• no of deaths = 1500 per year
• 10,000 to 20,000 hospitalisations per year.

Both have been increasing over the last 30 years

Diagnosis is typically seen in individuals who began working with asbestos prior to the 1980s and are now usually more than 50 years of age

Question 6

What kind of work increases a patient’s risk of asbestosis?

Answer 6

shipyard, construction, maintenance, vehicle brake mechanic, asbestos cement, insulation or production of tiles, shingles, gaskets, brakes or textiles

Question 7

What are the presenting symptoms of asbestosis?

Answer 7

• dyspnoea on exertion
  
  • ​1st sign of asbestosis
  • increases with progression of disease
  • absent in those with just pleural changes
• cough
  
  • ​Dry, non-productive cough; frequency increases with progression
  • productive cough if pt also developed COPD
• chest pain
  
  • Not typically seen in patients with asbestosis or pleural changes.
  • Symptoms of chest tightness from shortness of breath may be confused with chest pain.

Question 8

In pts with exposure to asbestos, what symptom would raise the suspicion of mesothelioma?

Answer 8

Severe unremitting chest raises concern

Question 9

What are the signs of asbestosis O/E?

Answer 9

• crackles O/A
  
  • Initially heard at bases and increases with progression of disease.
  • It can be absent in patients with early asbestosis
  • is absent in patients with pleural changes alone.
• clubbing

Question 10

What are some primary investigations for ?asbestosis

Answer 10

• CXR PA & lateral
  
  • It is less sensitive than a CT scan and more specific than pulmonary function testing
  • should show:
    
    • lower zone linear interstitial fibrosis;
    • progressively involves the entire lung;
    • pleural thickening
• Lung function tests
  
  • should show
    • restrictive changes;
    • may have obstructive picture (especially if history of asbestos exposure and smoking)

Question 11

What do the flow volume loops derived from lung function testing look like in

a) restrictive disease
b) obstructive disease

Answer 11

Question 12

How does

a) FEV1
b) FEV1/FVC ratio

look in obstructive disease and restrictive disease?

Answer 12

Restrictive:

• reduced FVC
• normal FEV1/FVC ratio
• reduced slow vital capacity (SVC)
• reduced TLC
• reduced lung diffusion capacity testing (DLCO).

Obstructive changes:

• reduced FEV1,
• reduced FEV1/FVC ratio,
• increased RV/TLC ratio,
• reduced DLCO.

Question 13

Which parameter that changes in restrictive disease is the most sensitive?

Answer 13

reduced lung diffusion capacity testing (DLCO).

Question 14

What are some possible secondary investigations for ?asbestosis

Answer 14

• High-resolution CT chest
  
  • ​more sensitive than CXR
  • should show lower zone linear interstitial fibrosis; progressively involves the entire lung; pleural thickening
• lung biopsy
  
  • ​Open lung biopsy is rarely needed for diagnosis
  • used only when cancer is suspected/diagnosis is uncertain
  • Bronchoscopic biopsy generally provides insufficient tissue to rule out asbestosis and is limited to evaluation for cancer, or if other clinical conditions are suspected.
  • Quantification of the mineral content is the most sensitive procedure.
• bronchial lavage
  
  • presence of asbestos bodies in lavage fluid
  • but absence does not rule out asbestosis

Question 15

What is mesothelioma?

Answer 15

Malignant mesothelioma is an aggressive epithelial neoplasm arising from the lining of: (mesothelium)

• lung
• abdomen
• pericardium
• tunica vaginalis.

It is one of the few cancers related directly to an environmental exposure; asbestos is the chief causative agent

Question 16

What is the aetiology of mesothelioma?

Answer 16

• Exposure to asbestos is the principal risk factor; about 80% of patients have a history of asbestos exposure
  
  • As of 2013 approximately 125 million people have been exposed to asbestos at work.
  • Moreover, 50,000 people had malignant mesothelioma and 34,000 died from the disease
• prior exposure to radiotherapy (a known carcinogen);
• genetic predisposition e.g., mutation of the BAP1 gene
• simian virus 40 (SV-40)
• Germline mutations in the gene encoding BRCA1 associated protein-1 (BAP1) can predispose carriers to mesothelioma.
  
  • Other cancers, in particular uveal and cutaneous melanomas, basal cell carcinomas, and renal cell carcinomas, have been described in these individuals

Question 17

Name some risk factors for mesothelioma

Answer 17

• asbestos exposure
• age 60 to 85 years
  
  • due to 20-40yr latency period

weak:

• asbestos exposure during home maintenance and renovation
• male sex
• radiation exposure
• genetic predisposition
• simian virus 40 (SV-40)

Question 18

Summarise the epidemiology of mesothelioma

Answer 18

• The disease is more common:
  
  • men
  • white people,
  • older adults (sixth to ninth decade of life)
• In the UK, the incidence has been increasing rapidly since the 1960s, when the mesothelioma register was established to record cases.
• Currently it is projected that the annual number of deaths in the UK will peak some time between the years 2011 and 2015, with 1950 to 2450 deaths

Question 19

Fx of which cancers suggests a germline BAP-1 mutation?

Answer 19

• uveal melanoma
• renal cell carcinoma
• cutaneous melanoma

Question 20

What are the presenting symptoms of mesothelioma?

Answer 20

• shortness of breath
• chest pain
  
  • 25% of patients
• cough
  
  • dry and non-productive
• constitutional symptoms
  • non-specific findings such as fatigue, fever, sweats, and weight loss.

Question 21

What are the signs of mesothelioma O/E?

Answer 21

• diminished breath sounds O/A
  
  • Usually a result of pleural effusion, trapped lung, or bronchial obstruction
• dullness to percussion
  
  • Suggests presence of a pleural effusion on the affected side
• rarely abdominal distension and/or pain
  
  • late presentation of mesothelioma
  • but common presentation of peritoneal mesothelioma

Question 22

What are some primary investigations for ?mesothelioma

Answer 22

• CXR
  
  • = unilateral pleural effusion and irregular pleural thickening
  • • reduced lung volumes, and/or parenchymal changes related to asbestos exposure (e.g., lower zone linear interstitial fibrosis)
  • but visualises the pleura poorly and will miss subtle abnormalities
• CT scan of the chest & upper abdomen w iv contrast
  • = pleural thickening and/or discrete pleural plaques, pleural and/or pericardial effusions;
  • • enlarged hilar and/or mediastinal lymph nodes;
  • • chest wall invasion and/or spread along needle tracts can occur
  • ​more sensitive, providing more detail of the pleura, lungs, and mediastinum.
  • but differentiating benign from malignant pleural processes with CT alone can be difficult

Question 23

What are some possible secondary investigations for ?mesothelioma

Answer 23

• thoracentesis
  
  • exudate; may show malignant cells within the pleural fluid
  • but sensitivity is low
• pleural biopsy​
  
  • specimen for pathological diagnosis
• video-assisted thoracoscopic surgery (VATS)
  
  • Pleural biopsies performed during VATS exploration is the most invasive but also the most accurate modality
  • = pleural thickening or discrete plaques; lymphadenopathy
• immunohistochemistry
  
  • ​This should use selected markers expected to be positive in mesothelioma (e.g., calretinin, keratins 5/6, and nuclear WT1)
  • and markers expected to be negative in mesothelioma (e.g., CEA, EPCAM, claudin 4, TTF-1).
• chest MRI
  
  • MRI has the potential to differentiate between benign fibrous mesothelioma (low signal intensity on T2-weighted images) and malignant mesothelioma (high signal intensity)
  • but it is not as reliable as biopsy and will seldom alter management.
  • = but it is not as reliable as biopsy and will seldom alter management.
• PET scan
  
  • ​distinguish benign pleural abnormalities from malignant processes
  • can help define the extent of intrathoracic and mediastinal disease and detect regional and distant metastases
  • = can help define the extent of intrathoracic and mediastinal disease and detect regional and distant metastases
• cervical mediastinoscopy
  
  • = spread to mediastinal lymph nodes
• pulmonary function tests
  
  • ​ Patients with marginal function can be further assessed with radionuclide studies as needed.
  • In general, postoperative FEV1 and DLCO should be >40% of predicted values.
  • Spirometry is a sensitive predictor of postoperative complications after thoracotomy.
• FBC
  
  • Baseline blood counts are necessary before treatment is initiated or invasive procedures are performed.
  • Chemotherapy, and to a lesser degree radiotherapy, can decrease haematopoiesis, necessitating baseline and periodic analysis of blood counts.
• basic metabolic panel
  
  • Some chemotherapy agents, cisplatin in particular, can affect electrolytes and kidney function.

Question 24

What does this CXR show?

Question 25

What does this CXR show?