Non-Small Cell Lung Cancer Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Stage Information for NSCLC
Evidence (CT/FDG-PET scan):
- If there is no evidence of distant metastatic disease on CT scan, FDG-PET scanning complements CT scan staging of the mediastinum. Numerous nonrandomized studies of FDG-PET scanning have evaluated mediastinal lymph nodes using surgery (i.e., mediastinoscopy and/or thoracotomy with mediastinal lymph node dissection) as the gold standard of comparison.
- In a meta-analysis evaluating the conditional test performance of FDG-PET scanning and CT scanning, the median sensitivity and specificity of FDG-PET scans were reported as 100% and 78%, respectively, in patients with enlarged lymph nodes. FDG-PET scanning is considered very accurate in identifying malignant nodal involvement when nodes are enlarged. However, FDG-PET scanning will falsely identify a malignancy in approximately one-fourth of patients with nodes that are enlarged for other reasons, usually as a result of inflammation or infection.[15,16]
- The median sensitivity and specificity of FDG-PET scanning in patients with normal-sized mediastinal lymph nodes were 82% and 93%, respectively. These data indicate that nearly 20% of patients with normal-sized nodes but with malignant involvement had falsely negative FDG-PET scan findings.
For patients with clinically operable NSCLC, the recommendation is for a biopsy of mediastinal lymph nodes that were found to be larger than 1 cm in shortest transverse axis on chest CT scan or were found to be positive on FDG-PET scan. Negative FDG-PET scanning does not preclude biopsy of radiographically enlarged mediastinal lymph nodes. Mediastinoscopy is necessary for the detection of cancer in mediastinal lymph nodes when the results of the CT scan and FDG-PET scan do not corroborate each other.
Evaluation of brain metastasis
Patients at risk for brain metastases may be staged with CT or MRI scans. One study randomly assigned 332 patients with potentially operable NSCLC and no neurological symptoms to brain CT or MRI imaging to detect occult brain metastasis before lung surgery. MRI showed a trend towards a higher preoperative detection rate than CT scan (P = .069), with an overall detection rate of approximately 7% from pretreatment to 12 months after surgery. Patients with stage I or stage II disease had a detection rate of 4% (i.e., eight detections out of 200 patients); however, individuals with stage III disease had a detection rate of 11.4% (i.e., 15 detections out of 132 patients). The mean maximal diameter of the brain metastases was significantly smaller in the MRI group. Whether the improved detection rate of MRI translates into improved outcome remains unknown. Not all patients are able to tolerate MRI, and for these patients contrast-enhanced CT scan is a reasonable substitute.
Evaluation of distant metastasis other than the brain
Numerous nonrandomized, prospective, and retrospective studies have demonstrated that FDG-PET scanning seems to offer diagnostic advantages over conventional imaging in staging distant metastatic disease; however, standard FDG-PET scans have limitations. FDG-PET scans may not extend below the pelvis and may not detect bone metastases in the long bones of the lower extremities. Because the metabolic tracer used in FDG-PET scanning accumulates in the brain and urinary tract, FDG-PET scanning is not reliable for detection of metastases in these sites.