Preliminary Diagnosis: Non-Small Cell Lung Cancer
I. What imaging technique is first-line for this diagnosis?
- CT of the chest with intravenous contrast
II. Describe the advantages and disadvantages of this technique for diagnosis of non-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
- CT should include the 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
- Positive predictive value (PPV) of 50% and negative predictive value (NPV) of 85%
- Limited in detecting chest wall or parietal pleural invasion
- Limited in detecting extra-thoracic metastatic disease
- 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 trimester
- Contraindicated in patients with iodine allergies
- It should be used with caution in patients with acute renal insufficiency.
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 non-small cell lung cancer.
PET/CT
Advantages
- Delineates anatomy and also determines metabolic activity of suspicious lesions
- Improved sensitivity (98%) versus CT alone at identifying mediastinal invasion and lymph node metastases
- Improved sensitivity and specificity for detecting extrathoracic metastatic disease versus CT alone
- Can help determine locations for highest-yield biopsy, especially if considering invasive mediastinal lymph node staging
- Helpful when planning definitive courses of radiation and determining disease response to treatment
- Can drastically alter management by upstaging patients, making them inoperable, thus eliminating unnecessary surgery
Disadvantages
- Expensive and not easily accessible at certain medical centers
- High false positive rate (20%), which may require pathologic confirmation to rule out.
- PET scans alone (without CT hybrid) are not as sensitive in detecting mediastinal or extrathoracic metastases and often more difficult to elucidate anatomy
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
Disadvantages
- Loss of signal from physiologic lung movement
- Not as well tolerated in obese, claustrophobic, or patients with SOB or not able to hold breath
- More time consuming than CT
Chest X-ray
Advantages
- Cheap, easily accessible, easy to administer
- Requires lower dose of radiation exposure
- Helpful in comparing with previous films to determine if further workup is necessary
Disadvantages
- Unable to determine full staging
- Insufficient to assess mediastinal and lymph node metastases
- Cannot determine extrathoracic metastases
VI. What are the contraindications for the alternative imaging techniques?
PET/CT
- Because CT is a component of this imaging technique, it is contraindicated in pregnant women.
MRI
- Contraindicated in patients with pacemakers and other implantable, MRI-incompatible devices
- Since contrast is administered, caution should be used in patients with renal insufficiency
CXR
- There are no major contraindications for this imaging modality.
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