What is the role of imaging in the M classification of lung cancer staging?

Updated: Jan 28, 2019
  • Author: Omar Lababede, MD; Chief Editor: Eugene C Lin, MD  more...
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The detection of distant metastases is of crucial importance because it usually implies a poor prognosis. These patients are generally treated with chemotherapy and/or radiation, as curative surgical resection of the primary tumor is not a consideration.

Metastases occur in about 50% of patients with non–small cell lung cancer. The probability of metastases is highest forsmall cell lung cancer, which is 60-80% on presentation, and lowest for squamous cell cancers; the incidence increases with advancing stage. No such trend exists for cancer involving the other cell types.

Adenocarcinoma tends to metastasize to the brain and adrenals early in its course. In patients with clinical or biochemical evidence of disease elsewhere, targeted imaging of those sites is performed. These sites include the brain, which can be examined with CT scanning or MRI, and the skeleton, which can be examined with scintigraphy. Usually, these sites are not imaged in asymptomatic patients with non–small cell lung cancer.

With recent advances in MRI, whole body MRI with DWI is emerging as a single, cost-affective imaging technique comparable to that PET/CT for staging patients with metastatic carcinoma. [16]

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