Noninvasive clinical staging modalities for lung cancer

Lung cancer staging essentials: the new TNM staging system and potential imaging pitfalls

Lung cancer is the leading cause of cancer-related deaths worldwide, with a dismal 5-year survival rate of 15%. The TNM (tumor-node-metastasis) classification system for lung cancer is a vital guide for determining treatment and prognosis. Despite the importance of accuracy in lung cancer staging, however, correct staging remains a challenging task for many radiologists. The new 7th edition of the TNM classification system features a number of revisions, including subdivision of tumor categories on the basis of size, differentiation between local intrathoracic and distant metastatic disease, recategorization of malignant pleural or pericardial disease from stage III to stage IV, reclassification of separate tumor nodules in the same lung and lobe as the primary tumor from T4 to T3, and reclassification of separate tumor nodules in the same lung but not the same lobe as the primary tumor from M1 to T4. Radiologists must understand the details set forth in the TNM classification system and be familiar with the changes in the 7th edition, which attempts to better correlate disease with prognostic value and treatment strategy. By recognizing the relevant radiologic appearances of lung cancer, understanding the appropriateness of staging disease with the TNM classification system, and being familiar with potential imaging pitfalls, radiologists can make a significant contribution to treatment and outcome in patients with lung cancer.

Prevalence of noncardiac findings on low dose 64-slice computed tomography used for attenuation correction in myocardial perfusion imaging with SPECT

Electrocardiogram (ECG)-triggered, low dose computed tomography (CT) is increasingly used for attenuation correction in myocardial perfusion imaging (MPI) with SPECT. The purpose of the study was to assess the prevalence of relevant noncardiac findings in the field-of-view of such attenuation correction CT scans. Five hundred and eighty-two consecutive patients (211 female, 371 male; mean age: 64 +/- 11 years; BMI: 27.7 +/- 5.3 kg/m(2)) underwent 64-slice, ECG-triggered CT scanning for attenuation correction of MPI with SPECT. Relevant findings were defined as abnormalities that required clinical or radiological follow-up. Noncardiac findings were detected in 400 patients (68.7%). In 196 patients (33.7%) 226 relevant findings were detected. Findings included noncalcified pulmonary nodules (n = 156), interstitial lung disease (n = 6), pleural effusion (n = 20), pneumonia (n = 1), aortic aneurysm (n = 5), aortic dissection (n = 4), enlarged mediastinal lymph nodes (n = 5), mediastinal tumor (n = 3), breast abnormalities (n = 3), liver cirrhosis (n = 5), liver mass (n = 5), ascites (n = 5), splenomegaly (n = 2), renal mass (n = 1), hydronephrosis (n = 1), adrenal mass (n = 3), and bone metastasis (n = 1). As low dose 64-slice CT scans used for attenuation correction in MPI with SPECT reveal a high prevalence of noncardiac pathologic findings with potential clinical relevance, a systematic review of the CT scans appears mandatory.

Lymph node size and metastatic infiltration in non-small cell lung cancer

BACKGROUND

Preoperative lymph node staging of lung cancer by CT relies on the premise that malignant lymph nodes are larger than benign ones. Lymph nodes > 1 cm in size are regarded as metastatic nodes. The surgical approach and potential application of neoadjuvant therapy regimens are dependent on this evaluation.

PATIENTS AND METHODS

In a morphometric study, hilar and mediastinal lymph nodes from 256 patients with non-small cell lung cancer (NSCLC) were analyzed. The lymph nodes were counted, the largest diameter of each lymph node was measured, and each lymph node was analyzed for metastatic involvement by histopathologic examination. The frequency of metastatic involvement was calculated and correlated with lymph node size. Preoperative CT scans of 80 patients were retrospectively analyzed by a staff radiologist. Lymph node size was measured, and lymph nodes were evaluated due to radiologic criteria. The radiologic evaluation was compared to the histopathologic diagnosis.

RESULTS

A total of 2,891 lymph nodes were present in the 256 specimens examined for this study. One hundred thirty-nine patients had a pN0 status, whereas 117 patients had lymph nodes that were positive for cancer. Two thousand four hundred eighty-six lymph nodes (86%) were tumor-free, while 405 (14%) showed metastatic involvement on histopathologic examination. The mean (+/- SD) diameter of the nonmetastatic lymph nodes was 7.05 +/- 3.75 mm, whereas infiltrated nodes had a diameter of 10.7 +/- 4.7 mm (p = 0.005). One thousand nine hundred fifty-three of the tumor-free lymph nodes (79%) and 170 of the metastatic lymph nodes (44%) were < 10 mm in diameter. Of 139 patients with no metastatic lymph node involvement, 101 (77%) had at least one lymph node that was > 10 mm in diameter. Of 127 patients with metastatic lymph node involvement, 12% had no lymph node that was < 10 mm. The independent radiologic evaluation of the CT scans of 80 patients yielded a sensitivity of 57.1% and a specificity of 80.6%.

CONCLUSION

Lymph node size is not a reliable parameter for the evaluation of metastatic involvement in patients with NSCLC.