Lung Cancer Flashcards
Incidence and prevalence of lung cancer
-Lung cancers arise from malignant epithelial cells in the lungs. Globally, lung cancer is the most common cancer (11.6% of new cancer diagnoses) and is the leading cause of cancer death (18.4% of total cancer deaths).
-In the UK, the incidence of lung cancer is 43,000. 3rd most common behind breast and prostate. On average, a full-time general practitioner diagnoses approximately one case of lung cancer every year.
-Despite its prevalence, lung cancer has a poor prognosis, with a 5-year survival rate of 17%
Classification of lung cancers
-Small cell 10-15%
=Located centrally, poorly differentiated
=More common in older smokers
=Metastasise early, more aggressive
=Secrete ATCH (Cushing’s) and ADH (SIADH), associated with Lambert-Eaton syndrome
=Chemo with or without radiation
-Non small cell 85-90%.
=Adenocarcinoma 40%: peripheral (in smaller airways), glandular differentiation. More common in non-smokers, Asian female. Met early. Responds well to immunotherapy
=Squamous cell carcinoma 20%: centrally in bronchi, squamous differentiation (keratinisation). Smokers. Secrete PTHrP causing hypercalcaemia, met ate (via lymph nodes). Paraneoplastic syndromes.
=Large cell carcinoma 10%: central and peripheral, large and poorly-differentiated, smokers, met early
-Mesothelioma: pleural based associated with Asbestos exposure. Latent presentation, poor prognosis
Overview of squamous cell cancer
=typically central
=associated with parathyroid hormone-related protein (PTHrP) secretion → hypercalcaemia
=strongly associated with finger clubbing
=cavitating lesions are more common than other types
=hypertrophic pulmonary osteoarthropathy (HPOA)
Overview of adenocarcinoma
=typically peripheral
=most common type of lung cancer in non-smokers, although the majority of patients who develop lung adenocarcinoma are smokers
Overview of large cell lung carcinoma
=typically peripheral
=anaplastic, poorly differentiated tumours with a poor prognosis
=may secrete β-hCG
Risk factors of lung cancer
-The main risk factor is tobacco smoking, which is associated with 80% of lung cancer cases.
-Other important risk factors include:
=Air pollution (indoor and outdoor)
=Family history of cancer, especially lung cancer
=Male sex
=Radon gas (typically affects miners)
=Asbestos exposure (In case of mesothelioma)
History of lung cancer
-Typical symptoms of lung cancer include:
=Unexplained cough for at least 3 weeks (with or without haemoptysis)
=Recurrent pneumonia
=Unintended weight loss (>5% in 6 months)
=New-onset dyspnoea
=Pleuritic chest pain (due to the tumour invading the pleura or the chest wall)
=Bone pain (due to metastases – commonly the spine, pelvis and long bones)
=Fatigue (due to anaemia of chronic disease)
=Note that up to 20% of patients present with non-respiratory symptoms (such as fatigue). Weight loss
-Family history: lung cancer in a first-degree relative is associated with a doubling in the risk of developing lung cancer.
-Smoking history: quantify in pack-years (1pack-year = smoking 20 cigarettes a day for a year). Also ask about passive smoking(second-hand smoking), as this can cause lung cancer.
-Occupation: may be exposed to indoor air pollution or radon gas (e.g. miners)
Physical examination of lung cancer
-A focused respiratory exam would be appropriate, with emphasis on palpation of lymph nodes, especially in the supraclavicular and cervical regions.
-Extra-respiratory physical findings should also be assessed such as weight loss or bony pain secondary to metastases.
-There may be unilateral pleural effusion or signs of consolidation or collapse of a lobe of the lung. Other findings may include cachexia, Horner’s syndrome, enlarged supraclavicular nodes, recurrent laryngeal nerve paralysis, SVC syndrome and HPOA. Finger clubbing and lymphadenopathy (supraclavicular)
-Absence of clinically significant findings does NOT rule out the diagnosis of lung cancer
Presentations of lung cancer
-Non-metastatic manifestations
-Horner’s syndrome (ptosis, anhidrosis, miosis: Pancoast tumour)
-Endocrine complications (SIADH, Cushing’s, hypercalcaemia)
-Paraneoplastic syndromes (limbic encephalitis: anti Hu antibodies)
-Neurological complications (recurrent laryngeal nerve palsy: hoarse voice/ phrenic nerve palsy: SOB as diaphragm weakness)
=Polyneuropathy (caused by antibodies formed against myelin sheath)
=Lambert-Eaton myasthenic syndrome (weakness in proximal muscles, diplopia, ptosis, slurred speech, dysphagia, autonomic dysfunction)
=Cerebellar degeneration
-Respiratory symptoms of persistent dry cough, haemoptysis, wheezing, “recurrent” pneumonia or dyspnoea.
=a. Worsening of pre-existing COPD
=b. Feeling of fullness in the chest or even severe pain
=c. Change in character of smoker’s cough and pattern of dyspnoea
=d. Occasionally stridor or wheeze
-Systemic symptoms of weight loss, fevers, clubbing or fatigue
-Symptoms from local compression: chest pain, bone pain, SVC obstruction, and dysphagia
Describe lung cancer endocrine complications
-Syndrome of inappropriate ADH secretion presents itself with hyponatraemia.
-Cushing’s syndrome is caused by ectopic ACTH secretion.
-The clinical features are similar to Cushing’s syndrome caused by other causes but in lung cancer often there is concomitant MSH production leading to skin pigmentation.
-Excessive secretion of parathormone related protein leads to hypercalcaemia. Hypercalcaemia may also occur as a consequence of lytic bone metastases. Almost all the endocrine and non-endocrine paraneoplastic syndromes are frequently seen in SCLC
Describe lung cancer paraneoplastic syndrome
-Paraneoplastic syndrome is a non-endocrine, non-metastatic complication of lung cancer.
-Paraneoplastic syndrome can present themselves years before, at the time of, or subsequent to the diagnosis of lung cancer
Describe Lambert-Eaton myasthenic syndrome
-Caused by an autoimmune reaction in which antibodies are formed against presynaptic voltage gated calcium channels in the neuromuscular junction.
-The most frequent consequence is muscle weakness of limbs
Describe cerebellar degeneration
-This is an autoimmune reaction targeted against Purkinje cells of cerebellum.
-Neurological symptoms present insidiously and progress rapidly to a severely disabled state.
-Clinical findings include cerebellar ataxia, dysarthria, vertigo, diplopia, nystagmus and emesis
Referral criteria lung cancer
The NICE guidelines on suspected cancer (updated December 2021) recommend offering a chest x-ray, carried out within 2 weeks, to patients over 40 with:
=Clubbing
=Lymphadenopathy (supraclavicular or persistent abnormal cervical nodes)
=Recurrent or persistent chest infections
=Raised platelet count (thrombocytosis)
=Chest signs of lung cancer
-Refer people using a suspected cancer pathway referral (for an appointment within 2 weeks) for lung cancer if they:
=have chest x-ray findings that suggest lung cancer
=are aged 40 and over with unexplained haemoptysis
Investiagtions of Lung Cancer
- CXR and if any abnormalities on chest x-ray then a CT scan of the chest. A normal CXR does not mean any further investigation in the presence of persistent symptoms in a smoker over the age of 40. CXR will only demonstrate approximately 60% of lung cancers, as the remainder are too central to be seen on lung fields. Hilar enlargement, peripheral opacity, pleural effusion (unilateral), collapse
- CT Scans of chest and upper abdomen: The soft tissue windows will demonstrate any hilar, mediastinal or subcarinal nodes. Also liver and adrenal metastases can be visualised. Lung windows may show other nodules, which may be metastases. Bone windows may show any possible bony metastases. Contrast-enhanced
- Sputum cytology if available.
- In all cases of haemoptysis and in most cases of “central” lung cancer a fibre-optic bronchoscopy with brushings, washings and biopsies as appropriate. Use of endobronchial ultrasound guided biopsy of central lymph nodes in experienced hands may be another method of obtaining cytological confirmation of lung cancer. Mediastinoscopy may still have a role in staging lung cancer but is nowadays being increasingly supplanted by PET/CT scans.
- CT guided percutaneous biopsy of peripheral lesions, not within reach of a bronchoscope.
- Once a diagnosis of lung cancer is made a PET/CT scan may give information about distant spread of lung cancer.
- Standard haematology and biochemistry particularly looking at serum calcium and sodium levels as well as any hepatic or renal dysfunction
