There are many different strands of cancer research we can be sure are being conducted simultaneously. Some members of the public may imagine cancer research to be all about creating a myriad of new therapies in the hopes that one will prove to be able to effectively “cure” cancer. However, there is a type of cancer research that receives less attention: the appraisal of current imaging guidelines and updating them according to the best and latest evidence.
In this article, we will be reviewing common imaging modalities used in patients with medullary thyroid carcinoma (MTC) and discussing their merits and limitations.
Many Ways Of Seeing
One of the cheapest imaging modalities (across multiple disciplines) is the humble ultrasound scan. Its main advantages are that it is noninvasive and can be done in a bedside setting, which can be useful for triage purposes in the emergency department. In the case of MTC, neck ultrasound scans can give physicians an overview of what they are dealing with: the size of the tumor, its location, any local metastases, and so on.
“Neck ultrasound is the golden imaging modality for evaluation, localization and characterization of thyroid nodules and neck lesions,” Klain et al wrote in their study on medical imaging for MTC patients.
Because it allows physicians to visualize the extent of the tumor in the neck, as well as identify any recurrence of neck lesions, it is immensely useful in guiding sound clinical decision-making. In addition, neck ultrasounds are indispensable when performing fine needle aspirations of thyroid nodules or suspicious lymph nodes.
From the neck, the physician performing the ultrasound can quickly move to the abdomen to perform an ultrasound scan of the liver. This may be useful for detecting any metastases of the primary tumor to the liver. Oftentimes, tiny liver lesions may present in a manner similar to hepatic hemangiomas.
In a study looking at imaging modalities for neuroendocrine neoplasms (of which MTC is a type), Refardt and colleagues spent a section substantially discussing the merits of CT scans.
“CT shows a high-detection sensitivity for the majority of neuroendocrine neoplasms and is the recommended morphological imaging technique,” they wrote. “CT is the main modality used for the evaluation of neuroendocrine neoplasms due to its wide availability, speed, and low cost.”
Read more about MTC diagnosis
Contrast-enhanced chest CT scans can yield important information regarding thoracic tumors. For example, they are excellent for visualizing cervical and mediastinal lymph nodes that have a diameter larger than 1 cm. In addition, they can be used to detect lung metastases, including lesions that are relatively small in size (which is frequently the case for lung metastases).
The other imaging modality that has become indispensable in cancer imaging is MRI. MRI has always been superior to CT for soft tissue visualization, especially for organs such as the bone, liver, pancreas, and brain. Klain and colleagues wrote that in MTC patients, MRI can be particularly useful in defining the extent of the disease in the neck and mediastinum. However, MRI scans do typically take longer than CT scans, which can be a disadvantage in certain circumstances.
Both sets of authors recognized the important role that MRI plays in imaging the liver. “MRI of the liver is particularly useful during the treatment of liver metastases with tyrosine kinase inhibitors because these metastases may become difficult to visualize on multiphase contrast-enhanced CT scan,” Klain et al wrote.
Refardt and colleagues noted that “MRI has the additional advantage of an available hepatocyte-specific contrast medium” and that “it does not expose patients to radiation, which makes it an especially attractive imaging tool for regular surveillance in younger patients.”
Since MRI of the neck, mediastinum, and the liver is typically carried out in MTC patients, some physicians prefer to conduct whole-body MRI scans to avoid missing anything.
Refardt et al devoted much of their paper to the imaging possibilities for the different types of neuroendocrine tumors, while Klain and colleagues focused on imaging modalities useful specifically for MTC, such as somatostatin receptor imaging, PET scans, and the use of artificial intelligence.
Read more about MTC patient education
Regardless of the imaging modality under discussion, 2 parameters are constantly being used to evaluate their clinical usefulness: their specificity and sensitivity. Specificity is the ability of a test to identify true positives of a disease under investigation; sensitivity is the ability of a test to identify true negatives of the same disease. Any novel imaging modality must demonstrate its reliability through these 2 important measures.
Both research teams ended their studies emphasizing that imaging modalities should be tested in real-world clinical settings, with clearly defined patient-relevant outcomes. Prospective trials should be designed in such a way as to prove statistically significant clinical benefit; before that threshold is reached, much can be said to be speculative in nature.
Klain M, Hadoux J, Nappi C, et al. Imaging medullary thyroid cancer patients with detectable serum markers: state of the art and future perspectives. Endocrine. Published online November 8, 2021. doi:10.1007/s12020-021-02930-8
Refardt J, Hofland J, Wild D, Christ E. New directions in imaging neuroendocrine neoplasms. Curr Oncol Rep. Published online November 4, 2021. doi:10.1007/s11912-021-01139-2