Current uses of CT and MR imaging in the staging of lung cancer.

In 1986, Pearson reported on the lung cancer experience in Toronto over the past 25 years. The number of unresectable operations had decreased from 25 to 5%. Operative mortality was down from 10 to 3% and 5-year survival increased from 23 to 40%. The reason for these statistics, he stated, was not better surgery but better selection of surgical candidates, due to invasive and noninvasive techniques. CT and MR imaging are part of those noninvasive techniques and also play an important role in guiding the invasive techniques. Although controversy exists regarding the proper size criteria and axis length in nodal assessment, and the use of imaging in staging T1N0M0 lung cancer, most clinicians rely on CT scans to evaluate the patient with lung cancer. No other imaging test is as comprehensive in evaluating the patient with lung cancer. The main role of MR imaging at this time is as a problem-solving tool. Focused MR imaging examinations should be used to evaluate or to resolve specific questions related to invasion of the chest wall, vascular structures, or brachial plexus, and adrenal mass characterization. MR imaging is also useful in evaluating the hilum and mediastinum in patients who cannot receive intravenous contrast for CT evaluation. The overall accuracy of CT and MR imaging is disappointing, particularly in crucial areas of determining operability such as distinguishing between patients with Stage IIIA or IIIB disease. It is unlikely that CT diagnosis can significantly improve; however, there is substantial potential for improved diagnostic accuracy with MR imaging as continued research moves this technology forward. The future may bring improved tissue characterization and vascular evaluation. At present, CT remains the procedure of choice in the initial assessment of the patient with lung cancer. The radiologist must be prepared to interpret these imaging studies in light of the specific findings that determine the stage and thus potential resectability of lung cancer.