Lung Cancer

Snapshot

• A 69-year-old male with a 50 pack-year smoking history presents to his physician with complaint of worsening cough. He describes frequently coughing up blood in the past few weeks. He has unintentionally lost about 10 pounds of weight in the past month and has felt more fatigued than usual. On physical examination, he has ptosis and a constricted pupil in his left eye. His right eye is normal. A chest radiograph is obtained and is shown in the image. 

Introduction

• Overview lung cancer is a malignancy that affects the lung parenchyma or airways
  • most lung cancers can be divided into
    • small cell lung cancer 
    • non-small cell lung cancer
• Epidemiology
  • incidence
    • second most common cancer
    • leading cause of cancer-related death
  • risk factors
    • cigarette smoking
      • most important risk factor
      • second-hand smoke exposure is also a risk factor
    • asbestos
    • radon
    • family history of lung cancer
• Prognosis
  • depends on cancer type and severity
• Screening
  • performed with a low-dose computerized tomography (CT) scan of the chest
    • indicated in patients 55-80 years of age who have a 30 pack-year smoking history and either of the following
      • currently smoke
• has quit smoking within the past 15 years

Classification

Small Cell Lung Cancer (SCLC)
Type	Location	Associated Findings
Small cell (oat cell) lung cancer	Central	MYC gene amplicationMay produceadrenocorticotropic hormone (ACTH)leads to Cushing syndromeexcessive anti-diuretic hormone (ADH)leads to syndrome of inappropriate ADH (SIADH)presynaptic calcium channel antibodiesleads to Lambert Eaton syndrome

Non-Small Cell Lung Cancer (NSCLC)
Type	Location	Associated Findings	Histology
Adenocarcinoma	Peripheral	Most common  cause of lung cancer in non-smokerscause of lung cancer (excluding metastasis)Adenocarcinoma in situtumor growth along alveolar structureslepidic growth patternPatients may have hypertrophic osteoarthropathyCommon gene mutations includeKRASEGFRALK	Typically mucin positive and has a glandular appearance
Large cell carcinoma	Peripheral	Associated with a poor prognosisHighly associated with smoking	Pleomorphic giant cells
Squamous cell carcinoma of the lung	Central	Can arise from the bronchus	Keratin pearls  Intracellular bridges
Bronchial carcinoid tumor	Central or peripheral	Carcinoid syndromeBetter prognosis	Neuroendocrine cellsChromogranin A positive

Presentation

• Symptoms
  • cough
  • wheezing
  • unintentional weight loss
  • hemoptysis
  • chest pain
  • dyspnea
  • hoarseness
    • suggests involvement of the recurrent laryngeal nerve
• Physical exam
• finger clubbing 

Imaging

• Radiography 
  • indication
    • initial imaging modality when evaluating a patient with symptoms concerning for lung cancer
      • very important to review previous chest imaging to assess for lesion properties and changes 
• Computerized tomography (CT) scan
  • indication
    • perform with low-doses to screen for lung cancer (review “screening” in the introduction)
    • further evaluate pulmonary nodule found on radiography
• chest CT should be obtained for all patients with an unclearly characterized solitary pulmonary nodule seen on radiography

Studies

• Laboratory testing
  • complete blood count
  • liver function tests (e.g., alanine aminotransferase, aspartate aminotransferase, and total bilirubin)
    • abnormalities may suggest liver metastasis
  • alkaline phosphatase
    • abnormalities may suggest liver or bone metastasis
      • a gamma-glutamyl transpeptidase (GGT) should be obtained to differentiate between liver or bone involvement
  • calcium
    • abnormalities may suggest bone metastasis or paraneoplastic syndromes 
• Pulmonary function tests
• Evaluation of an incidental solitary pulmonary nodule
  • introduction
    • benign features
      • diffuse
      • central
      • popcorn
      • concentric
    • malignant features
      • ground-glass
      • eccentric
  • solitary pulmonary nodule < 8mm
    • if there are or are not risk factors, one typically does surveillance with a chest CT in a few months depending on the size of the lesion
  • solitary pulmonary nodule > 8mm
    • very low probability of malignancy
      • CT surveillance 
    • low/moderate probability of malignancy
      • positron emission tomography (PET) scan
        • if absent or mild uptake
          • CT surveillance
        • if moderate or intense uptake
          • biopsy or video-assisted thoracoscopic surgery
    • high probability of malignancy
• staging evaluation with or without PET scan

Differential

• Tuberculosis
  • differentiating factors
    • abnormal quantiferon or purified protein derivative (PPD) test
• history of ↑ risk of exposure (e.g., household contact with someone with diagnosed tuberculosis or travel to tuberculosis-endemic area)

Treatment

• Small cell lung cancer
  • most cases are non-resectable and thus require chemotherapy (e.g., carboplatin and etoposide) 
• Non-small cell lung cancer
  • treatment includes surgical removal, lymph node sampling or dissection, radiation, and chemotherapy
• depends on the staging

Complications

• Superior vena cava syndrome 
• Pancoast tumor 
  • may cause Horner syndrome
• Metastasis 
• Pericardial effusion
• Pleural effusion
• Paraneoplastic syndromes 
  • hypercalcemia of malignancy  
    • ectopic secretion of PTH-related protein (PTHrP)
  • Lambert-Eaton syndrome
  • SIADH
  • Cushing syndrome

Read Also: Ultimate USMLE Step 1 Study Notes