Lung Cancer

Fast Facts:   

• Leading cause of cancer deaths in the United States (more than breast, colorectal and prostate cancers combined).  
• An estimated 90% overall association with smoking.

Types:

Non-Small Cell Lung Cancer (NSCLC): ≈ 80%

• Adenocarcinoma (includes adenocarcinoma-in-situ, formerly known as “brochoalveolar carcinoma”)
• Squamous Cell
• Large Cell

Small Cell Lung Cancer (SCLC): ≈ 20%

Pulmonary Carcinoid: ≈ 2-3%

Typical Presentation:

Peripheral Mass: (usually NSCLC).

• Adenocarcinoma 
• Large Cell

Central Mass:

• Squamous Cell (NSCLC)
• Small Cell

Indications for PET/CT:

SPN: Characterization of a solitary pulmonary nodule (discussed here).

Lung Cancer (most commonly NSCLC):

• Initial Staging & Prognosis
• Radiation Treatment Planning
• Surgical Planning
• Assessing Response to Therapy (Early & Late)
• Evaluating Recurrence & Restaging

Evaluating Pleural Disease (discussed here)

• Thickening
• Effusions

Criteria for “Active Malignancy”:

• Any soft tissue density (well-defined or not) with metabolic activity above mediastinal blood pool should raise a suspicion for malignancy.
• The more focal the lesion and the more intense its uptake, the more likely the lesion is to be malignant.
• The presence of associated hypermetabolic nodes dramatically increases the likelihood of malignancy.

What We Report:  

The size, metabolic activity & location of the primary and representative metastatic lesions are reported.

Primary Lesion: Size, SUV & location – and its effects (e.g. obstructing bronchus, erosion through chest wall…).

Loco-Regional Disease: Hypermetabolic lymph nodes are the most common finding. 

Distant Disease: Most commonly metastasizes to the adrenal glands, liver, skeleton and brain.

Post-Therapeutic Inflammation/ Scarring: 

A significant percentage of NSCLC patients (and nearly all SCLC patients) will receive chemotherapy and/or radiation.  These treatments cause a significant (and fairly predictable) series of changes in both the primary tumor and surrounding pulmonary parenchyma (addressed in detail, here).  Familiarity with these changes is essential to accurately interpret these post-treatment scans.

False Positives:

Primary Lesion:

• Infection/Atelectasis/Pneumonia (covered here)
• Radiation Pneumonitis (covered here)
• Benign FDG-avid nodules (e.g. granulomas, hamartomas, infectious/inflammatory nodules) 

Nodes:

• Inflammatory nodes (covered here)

Pleura:

• Inflammatory pleural thickening (covered here)
• Pleurodesis (covered here)

False Negatives:

Lesions < 8.0 mm: Nodules less than 8.0 mm are “beneath the resolution of PET “ and are considered “indeterminate”, requiring follow up.

Weakly-Avid Tumors:  Adenocarcinoma-in-situ (formerly “bronchoalveolar carcinoma”) and carcinoid tumors often show only minimal FDG-uptake. Consequently, these two malignancies cannot be excluded for any mildly avid soft tissue density.  In such cases, we generally report:

 “…while its lack of significant metabolic activity suggests a benign finding, an indolent or low-grade malignancy such as an adenocarcinoma-in-situ cannot be excluded. Follow-up to resolution is recommended in this case.”