Epidemiology
Histologic Classification of Non-small Cell Lung Cancer 2
The major distinction in terms of both staging and therapy is between small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Our discussion focuses mainly on the NSCLC types.

FDG Uptake in Lung Cancer

Lung cancer is very FDG-avid. This uptake becomes even more conspicuous as there is relatively low uptake in the surrounding aerated lung as opposed to other soft tissues. Non-aerated lung may have about three times the activity of aerated lung. As lung tissue is less "dense", an area of atelectasis would have relatively higher uptake per volume of tissue compared to surrounding normal lung. This would hold true for a lung nodule as well. Therefore nodules should not be compared to surrounding aerated lung, but rather to other solid soft tissue to assess for relatively increased uptake. Comparison typically can be made with mediastinal soft tissues or blood pool.

Possible false negatives on FDG-PET:
1. Histologic types of lung cancer with variable uptake:
Should not be used to exclude these specific types


2. Necrosis 3. Size 4. Other lesions
SUV Criteria

Standardized Uptake Value takes into account the differences between normalizing for body weight, for lean body mass, or for surface area.

SUV calculation: SUV = [mCi/ml (decay corrected) in tissue] / [mCi of tracer injected/body weight (grams)]

Sensitivity and Specificity
Staging

TNM Staging in Non-Small Cell Lung Cancer

Tumor (T), node (N), metastasis (M) staging is used for non-small cell lung cancer 4.
Table 1: TNM Descriptors for Non-Small Cell Lung Cancer
Primary Tumor (T)
TX Primary tumor cannot be assessed, or tumor proven by the presence of malignant cells in sputum or bronchial washings but not visualized by imaging or bronchoscopy
T0 No evidence of primary tumor
Tis Carcinoma in situ
T1 Tumor = 3 cm in greatest dimension, surrounded by lung or visceral pleura, without bronchoscopic evidence of invasion more proximal than the lobar bronchus (i.e. not in the main bronchus)
T2 Tumor with any of the following features of size or extent:
  • 3 cm in greatest dimension
  • Involves main bronchus, = 2cm distal to the carina
  • Invades the visceral pleura
  • Associated with atelectasis or obstructive pneumonitis that extends to the hilar region but does not involve the entire lung.
T3 Tumor of any size that directly invades any of the following:
  • chest wall (including superior sulcus tumors), diaphragm, mediastinal pleura, parietal pericardium; or
  • tumor in the main bronchus < 2cm distal to the carina, but without involvement of the carina; or
  • associated atelectasis or obstructive pneumonitis of the entire lung
T4
  • Tumor of any size that invades any of the following: mediastinum, heart, great vessels, trachea, esophagus, vertebral body, carina; or
  • tumor with a malignant pleural or pericardial effusion, or with satellite tumor nodule(s) within the ipsilateral primary-tumor lobe of the lung
Regional Lymph Nodes (N)
NX Regional lymph nodes cannot be assessed
N0 No regional lymph node metastasis
N1 Metastasis to ipsilateral peribronchial and/or ipsilateral hilar lymph nodes, and intrapulmonary nodes involved by direct extension of the primary tumor
N2 Metastasis to ipsilateral mediastinal and/or subcarinal lymph node(s)
N3 Metastasis to contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular lymph node(s)
Distant Metastasis (M)
MX Presence of distant metastasis cannot be assessed
M0 No distant metastasis
M1 Distant metastasis present
Mountain et. al. 4

Table 2 - TNM Staging
Stage TNM 5-year Survival
0 Carcinoma in situ  
IA T1N0M0 67%
IB T2N0M0 57%
IIA T1N1M0 55%
IIB T2N1M0
T3N0M0
38%
IIIA T3N1M0
T1N2M0
T2-3N2M0
23%
IIIB T4N0-2
T1-4N3M0
5%
IV T1-4N0-3M1 1%


Table 3 - Staging-Tumor-Node Matrix6
The stages can also be shown as a tumor and node matrix.

N1 N2 N3 N4
T1 IA IIA IIIA IIIB
T1 IB IIB IIA IIIB
T1 IIB IIIA IIIA IIIB
T1 IIIB IIIB IIIB IIIB
T1 IA IIA IIIA IIIB

Therapy planning is determined by stage. Accurate staging is very important since it has such a major impact on both therapy and prognosis and FDG-PET plays an important role in selection of therapy.
Lymph Node Stations

Precise lymph node localization is useful for staging as well as for communication with the bronchoscopist or surgeon. A numbering system has been adopted to describe the various lymph node locations 5.

Table 4 - Lymph Node Stations
N1 Nodes
N1 nodes are designated with two digits.
N1 nodes must lie distal to the mediastinal pleural reflection
10 Hilar nodes Distal to the mediastinal pleural reflection, adjacent to the proximal lobar bronchi and the bronchus intermedius
11 Interlobar nodes Lying between lobar bronchi
12 Lobar nodes Adjacent to the distal lobar bronchi
13 Segmental nodes Adjacent to the segmental bronchi
14 Subsegmental nodes Around the subsegmental bronchi
N2 Nodes
N2 nodes stations are designated with a single digit.
N2 nodes must lie within the mediastinal pleural envelope
1 Highest mediastinal nodes Above the upper rim of the bracheocephalic (left innominate) vein where it ascends to the left, crossing in front of the trachea at its midline
2 Upper paratracheal nodes Below #1 and above the upper margin of the aortic arch
3 Prevascular and retrotracheal nodes 3A: prevascular;
3P: retrotracheal.
Midline nodes are ipsilateral for both sides
4 Lower paratracheal nodes Below #2 and above the upper margin of the upper lobe bronchus and on the left, medial to the ligamentum arteriosum.
5 Subaortic (aorto-pulmonary window) Lateral to the ligamentum arteriosum or the aorta or the left pulmonary artery, and proximal to the first branch of the left pulmonary artery
6 Para-aortic (ascending aorta or phrenic) Anterior and lateral to the ascending aorta and the aortic arch or the innominate artery beneath a line tangential to the upper margin of the aortic arch
7 Subcarinal nodes Caudal to the carina of the trachea, but not associated with the lower lobe bronchi or arteries within the lung
8 Paraesophageal nodes (below carina) Adjacent to the wall of the esophagus, excluding subcarinal nodes
9 Pulmonary ligament nodes Within the pulmonary ligament, including those in the posterior wall and lower part of the inferior pulmonary vein


Advantages of FDG-PET in Lymph Node Staging
Staging - Distant metastases
Radiation Therapy
Post Therapy
Post Operative Changes Post Radiation Changes Radiation Pneumonitis
Other Aspects
Conclusions