Initial Evaluation
Lung cancer may be suspected either because the patient presents with symptoms suggestive of cancer (e.g., cough, hemoptysis, dyspnea, weight loss), or because an abnormality was discovered incidentally (e.g., chest CT obtained in an asymptomatic patient for another reason) or through lung cancer screening.
During clinical evaluation, we maintain a high index of suspicion for nodal or metastatic disease. In patients suspected of having lung cancer, we typically obtain a complete blood count, electrolytes, calcium, alkaline phosphatase, alanine aminotransferase, creatinine, and albumin.
Radiological Imaging of Lung Cancer
The imaging approach for patients suspected of having lung cancer varies from center to center. Acceptable approaches should establish the highest radiological stage and identify the optimal biopsy site. Once imaging is completed, we proceed to choose an optimal biopsy site or surgical approach, details of which are discussed separately.
- Chest CT – Every patient suspected of having lung cancer should undergo a chest CT with contrast. The chest CT provides useful preliminary information on the stage of nodal tumor metastases (TNM), associated lung conditions, and potential biopsy targets.
Clinical Approach
This approach involves using thoracic computed tomography and clinical evaluation to determine if additional imaging should be performed to determine potential sites of metastases.
- The initial chest CT with contrast is evaluated to assess the extent of the primary tumor and its potential spread to the mediastinum, liver, thoracic skeleton, and adrenal glands.
- Additional imaging is performed in patients with focal symptoms, signs, or laboratory tests suggestive of metastatic disease and/or in patients with a high likelihood of having brain metastases (e.g., stage III or IV disease).
- Repeated or additional imaging is performed in patients when new symptoms appear (e.g., bone pain or headaches), rapid progression is suspected, or when there is a significant delay in the initiation of treatment of eight weeks or more.
The advantages of this approach include minimizing low-value testing. The limitations include the low sensitivity of chest CT for detecting nodal metastases, the need for confirmation by tissue sampling, and the possibility of missing occult disease.
Comprehensive Imaging Approach
This approach uses whole-body F18-fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT) with or without brain magnetic resonance imaging (MRI) to determine the most likely radiographic stage and optimal biopsy site.
- For patients in whom lung cancer is considered highly probable and in whom mediastinal or distant metastases are suspected (e.g., suspicion of stage III or IV disease) or in whom a diagnosis of lung cancer has already been made, an FDG-PET/CT is performed, even if a chest CT has already been obtained. When PET or integrated PET/CT is not available, conventional staging with abdominal CT and bone scintigraphy is sufficient, although less sensitive. This approach provides a comprehensive image-based lymph node analysis and is supported by data indicating that integrated PET/CT is superior to either modality alone for detecting occult disease.
- Patients with stage III or IV CT disease also generally undergo routine brain imaging with an MRI with gadolinium injection, or a CT with contrast if MRI is unavailable. This strategy also allows for early detection and treatment of brain metastases before the development of neurological deficits or seizures.
- For patients suspected of having localized stage lung cancer (e.g., stage I/II), imaging with whole-body FDG-PET/CT is controversial and depends on several factors, including radiographic stage, lesion size, and resectability. Many experts perform a PET/CT in this group of patients in the hope that PET/CT will further reduce the risk of unnecessary surgery and guide the optimal biopsy site. Other experts first perform a PET/CT selectively in certain patients (e.g., patients with signs of hilar nodes) or first perform tissue biopsy without PET/CT (e.g., patients with small lesions amenable to curative resection)
This approach is supported by the superior ability of PET/CT to detect occult disease compared to either modality alone and by conflicting data suggesting a possible reduction in potentially avoidable thoracotomies by detecting stage IV occult disease. The limitations of PET or PET/CT are the relatively high false-positive rate, the lack of standardized criteria regarding what constitutes a positive result, the low sensitivity for detecting brain metastases, the need for confirmation on tissue sampling, and issues related to third-party payer costs.
Diagnosis and Staging of Lung Cancer
A diagnosis of lung cancer is made based on the pathological evaluation of cytological (e.g., pleural fluid) or histopathological (e.g., tissue biopsy) samples. Consideration should be given to obtaining a sample large enough to allow for additional immunohistochemical (IHC) and genetic analysis.
Adenocarcinoma, squamous cell carcinoma, adenosquamous carcinoma, and large cell carcinoma are the four main histological subtypes of non-small cell lung cancer (NSCLC). The main entity in the differential diagnosis of NSCLC is small cell lung cancer (SCLC). Although clinical and imaging features may help the clinician distinguish NSCLC from SCLC, histopathological features and IHC markers are necessary to make this distinction.
Using radiological and pathological findings, lung cancer is staged using the eighth edition of the tumor, node, and metastasis system.
Source: UpToDate