Preliminary Diagnosis: Small Cell Lung Cancer

I. What imaging technique is first-line for this diagnosis?

CT of the chest with IV contrast.

II. Describe the advantages and disadvantages of this technique for diagnosing small cell lung cancer.

Advantages
  • Can adequately assess the T stage of the tumor.
  • Useful for identifying pleural nodules, pleural plaques, pleural/ pericardial effusions, or metastasis.
  • Higher sensitivity than PET/CT at visualizing brain metastases.
  • CT of the chest should include upper abdomen to assess for adrenal metastasis.
  • Easily accessible at most medical facilities.
  • Better tolerated in obese or claustrophobic patients.
Disadvantages
  • Low sensitivity (40-84%) and specificity (57-94%) for identifying mediastinal and lymph node involvement.
  • Limited in detecting chest wall or parietal pleural invasion.
  • Requires the use of IV contrast.
  • Exposure to ionizing radiation.

III. What are the contraindications for the first-line imaging technique?

  • Contraindicated in pregnant patients, especially during the first and second trimesters.
  • Relative contraindication in patients with iodine allergies.
  • Relative contraindication in patients with renal failure.

IV. What alternative imaging techniques are available?

  • PET/CT (commonly used as adjunct to chest CT for full staging)
  • MRI of chest
  • Chest X-ray

V. Describe the advantages and disadvantages of the alternative techniques for diagnosing small cell lung cancer.

PET/CT
Advantages
  • Delineates anatomy and also determines metabolic activity of lesions.
  • Improved sensitivity (98%) versus CT alone at identifying mediastinal invasion and lymph node metastases.
  • Improved sensitivity and specificity versus CT alone for detecting extrathoracic metastatic disease.
  • Can drastically alter management by correctly staging patients as limited or extensive stage, which ultimately dictates treatment course.
  • Helps with radiation treatment planning and assessing disease response after definitive therapy.
Disadvantages
  • Expensive and not easily accessible at certain medical centers.
  • Good positive predictive value, but poor negative predictive value.
  • High false positive rate, which may require further pathologic confirmation.
  • Sensitivity not as high in visualizing brain metastases.
MRI of chest/abdomen/brain with IV contrast
Advantages
  • Can help better assess extrathoracic and chest wall invasion.
  • Does not expose patient to ionizing radiation.
  • Can help delineate brain, adrenal, or spinal metastases.
  • Higher sensitivity than PET/CT at visualizing brain metastases
  • MRI of the brain with contrast should be obtained in all patients with suspected or confirmed diagnosis of small cell lung cancer prior to starting therapy
Disadvantages
  • Expensive.
  • Time consuming.
  • Requires significant patient cooperation to minimize motion artifact.
  • Loss of signal from physiologic lung movement.
  • Not as well tolerated in patients that are obese, claustrophobic, or unable to hold their breath.
Chest X-ray
Advantages
  • Cheap, easily accessible, and easy to administer.
  • Requires lower doses of radiation exposure.
  • Is helpful to compare with previous films to determine if further workup is necessary.
Disadvantages
  • Unable to determine full staging of disease.
  • Insufficient to assess mediastinal and lymph node metastases.
  • Cannot determine extrathoracic metastases.

VI. What are the contraindications for the alternative imaging techniques?

PET/CT
  • Contraindicated in pregnant women.
MRI chest/abdomen/brain with IV contrast
  • Contraindicated in patients with pacemakers and other implantable, MRI-incompatible devices.
  • Gadolinium contrast is contraindicated in patients with a GFR ≤ 30
CXR
  • There are no major contraindications for this imaging modality. Some institutions may require consent for pregnant patients.

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