Staging lung cancer

In non-small cell lung cancer (NSCLC), radical surgical resection is considered to represent therapy most likely to offer cure. This is usually only possible if there is no involvement of unresectable structures and no distant metastases. In advanced disease, particularly in the presence of distant metastases, cure is usually not possible and palliative chemotherapy and radiotherapy is considered the most appropriate therapeutic strategy. In small cell lung cancer (SCLC) treatment consists of chemotherapy with or without additional radiotherapy. In selected cases of disease limited to one hemithorax: radical surgery in combination with chemoand/or radiotherapy may provide curative treatment. The aim of staging procedures is to determine the extent of the disease and, thus, select the most appropriate treatment. For this purpose it is important to reliably detect local tumor extent (T stage: Tl-T4) as well as the presence or absence of lymphatic (N stage: NO-N3) and hematogeneous (M stage: MO, Ml) metastases (Table 1). Staging system


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In non-small cell lung cancer (NSCLC), radical surgical resection is considered to represent therapy most likely to offer cure. This is usually only possible if there is no involvement of unresectable structures and no distant metastases. In advanced disease, particularly in the presence of distant metastases, cure is usually not possible and palliative chemotherapy and radiotherapy is considered the most appropriate therapeutic strategy.
In small cell lung cancer (SCLC) treatment consists of chemotherapy with or without additional radiotherapy. In selected cases of disease limited to one hemithorax: radical surgery in combination with chemo-and/or radiotherapy may provide curative treatment.
The aim of staging procedures is to determine the extent of the disease and, thus, select the most appropriate treatment. For this purpose it is important to reliably detect local tumor extent (T stage: Tl-T4) as well as the presence or absence of lymphatic (N stage: NO-N3) and hematogeneous (M stage: MO, Ml) metastases (Table 1).

Staging system
Revisions in stage grouping of the TNM subsets in the international system for staging lung cancer were made 1997, to provide greater specificity for identifying patient groups with similar prognoses and treatment options. Patients who are likely to benefit from surgical resection are those with localized disease. Only stages I, II and IlIA can be considered as technically resectable (Table 2). Patients considered as definitely unresectable are those having distant metastases (Ml), controlateral or subclavian lymph node metastases (N3) or tumor classified T4.
The local extent of tumor affects the extent of surgery required for radical resection. Generally, a tumor sur- Owing to its superior contrast resolution, MR may demonstrate subtle chest wall invasion and be superior to CT in this regard. MR is also thought to be more accurate that CT in depicting chest wall invasion from superior sulcus tumor that commonly involves the vertebra posteriorly, and the subclavian vessels and brachial plexus anteriorly. On the other hand, using helical scanning with thin collimation, bolus injection of contrast medium, and sagittal and coronal reconstructions, the anatomical environment of the plexus may also be accurately assessed with CT. MR remains an alternative only in cases in which the CT findings are inconclusive and in those in which extension into the neural foramina and epidural space is suspected.
Both CT and MR! cannot reliably differentiate between benign and malignant pleural and pericardial effusions. Presence of malignant pleural or pericardial effusion is best diagnosed by demonstration of malignant cells at aspiration.

Nodal extent
CT is very valuable in detecting mediastinal lymph node enlargement. Low sensitivity of CT is due to its inability to detect microscopic metas-tases within normal-sized lymph nodes. Low specificity arises from the frequent occurrence of enlarged hyperplastic nodes. Consequently, all patients with abnormal mediastinal lymph nodes on CT scans need lymph node resection or biopsy. MR has no superiority over CT and is not indicated in this regard. Positron emission tomography (PET) with F-18 2 fluoro-2-deoxy-D-glucose (FDG) is more sensitive and specific than CT for nodal staging in lung cancer.
Mediastinoscopy has proven to be unnecessary in patients with CT evidence for stage I disease and a negative PET of the regional nodes. Increased FDG uptake in hilar and mediastinal lymph nodes can be used to direct surgical nodal sampling. The combined use of CT and PET to stage intrathoracic nodal metastases is not only clinically useful but also costeffective. PET reduces the probability that a patient with unresectable mediastinal nodal metastases will undergo an attempt at curative resection.

Distant metastases
In most institutions lung cancer patients undergo routine staging procedures including chest radiographs, CT of the chest, abdomen and brain, bone scintigraphy and ultrasound examination of the abdomen. Because the adrenal glands are the most common site for extrathoraeie metastases, CT examination should include the upper abdomen. An adrenal mass however may represent an incidental adenoma. Most incidental nonhyperfunctioning adrenal adenomas are less than 3 cm in diameter and of uniform low attenuation « 10 HU), because of their fat content. Routine unenhanced CT of the adrenal glands allows accurate prospective characterization of many adrenal masses in patients with lung carcinoma.
In institutions in which PET is readily available, this may be performed as the only additional examination after CT, as it is the most accurate non-invasive imaging technique to confirm or exclude both lymph node and distant metastases (except for brain metastases) in a single examination. Whole-Body FDG-PET improves the detection of extrathoracic disease and alters management in up to 40% of cases.

Conclusion
CT remains the imaging technique of choice in staging lung cancer. Despite its limitation, CT is indicated in order to determine the extent of the primary tumor, to evaluate the mediastinal space for the presence of nodal enlargement, and to screen metastatic disease in the adrenal glands. MR is only indicated as an additional examination in patients with superior sulcus tumor. Whole body PET is the best technique for screening both lymph node and distant metastases.