What is the role of MRI in the workup of small cell lung cancer (SCLC)?

Updated: Sep 12, 2019
  • Author: Abid Irshad, MD; Chief Editor: Eugene C Lin, MD  more...
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Answer

MRI is not routinely used for detecting the primary tumor or for staging. However, it may sometimes help in problematic cases because MRI offers improved tissue contrast resolution and a multiplanar imaging capability (see the image below). [36]  Brain MRI with IV contrast is recommended in all SCLC patients and has been shown to identify metastatic lesions in 10-15% of newly diagnosed SCLC patients without neurologic symptoms. Although most centers do not routinely use MRI to evaluate the primary lesion in the chest, it may provide useful information in problematic cases of mediastinal invasion. MRI does have a role in ruling out brain metastatic lesions and in differentiating questionable adrenal masses. In pregnant patients, MRI can also be used instead of CT scanning to avoid the potential effects of ionizing radiation. [26]  

MRI has a greater sensitivy than CT for intracranial metastases. In primary tumors, MRI can sometimes help differentiate tumor from surrounding atelectasis or pneumonitis, which has relatively high signal intensity on T2-weighted images, as opposed to the relatively low signal intensity of the tumor. [10, 11, 20, 24, 25]  Because of the relatively low spatial resolution of MRI compared with that of CT, a cluster of small lymph nodes may occasionally be mistaken for a single enlarged node. This observation can lead to a false-positive finding. Also, calcifications may be missed on MRIs.

Lung cancer, small cell. Contrast-enhanced MRI of Lung cancer, small cell. Contrast-enhanced MRI of the brain in a patient with known small-cell lung cancer (SCLC). Axial section at the level of lateral ventricles shows at least 2 ring-enhancing metastatic lesions in the periventricular region. The brain is one of the predominant sites for SCLC metastasis.

Gadolinium-enhanced MRI may also be helpful because the lung enhances rapidly, whereas the tumor usually enhances relatively slowly. MRI is also good for detecting nodes in the aortopulmonary window or for detecting subcarinal nodes, because it can provide images in the sagittal and coronal planes. With chemical shift imaging, MRI is reliable in differentiating adrenal adenomas from possible metastasis because it shows decreases in signal intensity on out-of-phase images as compared with in-phase images.

Gadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). NSF/NFD has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness.

In a study in which diffusion-weighted imaging (DWI) and short tau inversion recovery (STIR) turbo spin-echo imaging were compared in differentiating SCLC from NSCLC, DWI was found to be more useful than STIR. The specificity and accuracy were each 85.7% for DWI, whereas for STIR, specificity was 63.3% and accuracy was 66.1%. However, the accuracy was 94.6% when the 2 modalities were combined. [37]


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