In patients with newly diagnosed non-small cell lung cancer (NSCLC), approximately 30-50% of patients will develop brain metastases, which is associated with a worse prognosis.1 Early detection followed by aggressive treatment of both intracranial and systemic disease affords a survival benefit compared to delayed detection with the best medical therapy.2 Therefore, accurate staging of NSCLC patients is vital in order to achieve optimal outcomes. A recent comparison study evaluated the diagnostic performance of PET (positron emission tomography) -CT and whole body (WB) MRI in the staging of newly diagnosed NSCLC, and found them to be comparable. However, in the detection of metastases, each imaging modality had their individual merits and inherent limitations. One alternative option to overcome these limitations is co-registered WB MRI-PET imaging. This technique combines the functional evaluation of traditional PET scans with the anatomic resolution of MRI, making it an attractive option for metastatic surveillance.3
In a recent study, Yi et al evaluated the clinical effectiveness of integrated PET-CT plus a dedicated brain MRI with that of co-registered WB MRI-PET in the staging of clinically resectable NSCLC. They hypothesized that the incorporation of PET information into WB-MRI findings would increase the proportion of patients with correct upstaging compared with findings based on PET-CT or WB MRI alone.4 In this prospective study, 300 patients with newly diagnosed stage I, II, or IIIa NSCLC were randomized to receive either PET-CT plus brain MRI or co-registered WB MRI-PET (Figure 1). The primary outcome measure was correct upstaging of disease, which would lead to appropriate diagnosis and management, and avoid unnecessary thoracotomy.
Patients were considered to be over upstaged when WB imaging helped identify lesions with higher TNM classification, resulting in higher stage assignment, but the lesions proved to be benign on biopsy or other imaging modality studies. On the other hand, patients were defined as under staged when WB imaging failed to detect lymph node metastases that later had malignant cells identified with biopsy or imaging.
Thirty-seven of 143 (25.9%) patients randomized to coregistered WB MRI-PET were correctly upstaged, whereas 26 of 120 patients (21.7%) were correctly upstaged in the PET-CT plus brain MRI group. The upstaged difference between the two groups (4.2%) did not reach statistical significance. In the MRI-PET group, the cancer was under staged in 18 of 143 patients (12.6%) and overstaged in 26 of 143 patients (18.2%). In the PET-CT plus brain MRI group, the cancer was understaged in 28 of 120 patients (23.3%) and overstaged in 7 of 20 patients (5.8%).
Overall, the researchers were able to demonstrate that these staging tools, coregistered WB MRI-PET and PET-CT plus brain MRI, provide greater than 20% upstaging compared to conventional staging. However, preoperative staging with coregistered MRI-PET did not identify significantly more patients with NSCLC who have advanced-stage tumors, lymph nodes, or extrathoracic metastasis (correct upstaging) compared with PET-CT plus brain MRI. Additionally, their data demonstrate that the over staging of NSCLC observed in WB MRI-PET may lead to unnecessary and invasive staging workups. This study provides support for the use of PET-CT plus brain MRI for early detection of metastatic NSCLC with an acceptably low error rate.
1. Arrieta O, Villarreal-Garza C, Zamora J, Blake-Cerda M, et al.. Long-term survival in patients with non-small cell lung cancer and synchronous brain metastasis treated with whole-brain radiotherapy and thoracic chemoradiation Radiat Oncol. 2011;6:166.
2. Sheehan JP, Sun MH, Kondziolka D, Flickinger J, et al.. Radiosurgery for non-small cell lung carcinoma metastatic to the brain: long-term outcomes and prognostic factors influencing patient survival time and local tumor control. J Neurosurg. 2002 97(6):1276–1281.
3. Yi CA, Shin KM, Lee KS, et al.. Non-small cell lung cancer staging: efficacy comparison of integrated PET/CT versus 3.0-T whole-body MR imaging. Radiology. 2008;248(2):632–642.
4. Yi CA, Lee KS, Lee HY, Kim S, et al.. Coregistered whole body magnetic resonance imaging-positron emission tomography (MRI-PET) Versus PET-Computed Tomography Plus Brain MRI in Staging Resectable Lung Cancer. Cancer. 2013;119:1784–1791.