SPECT/CT Improves Thyroid Cancer Staging
A breakthrough in lymph node imaging in thyroid cancer using hybrid single photon emission CT and CT (SPECT/CT) has led to better assessment of recurrence risk and staging for treatment.
Using a SPECT/CT camera, researchers from the University of Erlangen-Nuremberg, Germany, were able to accurately distinguish malignant cells in regional lymph nodes from normal thyroid tissue in patients with differentiated thyroid carcinoma (DTC) treated with radioiodine. Researchers published their findings in the January issue of The Journal of Nuclear Medicine.
 Torsten Kuwert, M.D. University of Erlangen-Nuremberg, Germany |
DTC is the most common form of thyroid cancer, with more than 37,000 new cases forecast for 2009, according to the American Cancer Society. Because metastatic thyroid cancer has a high rate of recurrence, accurate confirmation of the spread of thyroid cancer cells to the regional lymph nodes is critical to disease treatment.
"Incorporated at first treatment, SPECT/CT allows us to better stratify patients into treatment groups," said senior author Torsten Kuwert, M.D., chair of clinical nuclear medicine at the university.
Researchers explored whether SPECT/CT would be more accurate than planar scintigraphy in the diagnosis of radioiodine-accumulating cervical lymph node metastases in a very early phase of management of patients with thyroid cancer, namely at radioablation of thyroid tissue usually performed several weeks after thyroidectomy.
The accuracy of planar imaging at that point is very low because radioiodine accumulation in the remnant is usually present and cannot be reliably distinguished from radioiodine-positive nodes with planar imaging, said Dr. Kuwert.
"We demonstrated that SPECT/CT fared significantly better than planar imaging to distinguish cancerous cells from residual thyroid tissue in a group of 57 patients," said Dr. Kuwert.
"Furthermore, our data show that SPECT/CT altered the risk classification conforming to the Union Internationale Contre le Cancer/American Joint Committee on Cancer (UICC/AJCC) in one out of four patients," he continued. "This in turn leads to a change in the strategy of follow up in these patients. With a better assessment of the individual patient's risk of recurrence, follow-up can be intensified in those upstaged and overtreatment avoided in those who get downstaged."
SPECT/CT Continues to Migrate into Clinical Practice
 54-year-old woman with differentiated papillary thyroid carcinoma (pT2N1a [6/21]Mx) after total thyroidectomy and lymph node dissection of centrocervical and left lateral compartment. (a) Planar scintigraphy shows two I-131-avid foci interpreted as thyroid remnant. (b) SPECT/CT (left column) and CT (right column) demonstrate that these foci correspond to lymph node metastases (LNMs) in superior mediastinum (level VII)—shown here for right focus. Image reprinted with permission of The Journal of Nuclear Medicine (JNM). Co-authors of "Impact of I-131-SPECT/Spiral-CT on Nodal Staging of Differentiated Thyroid Carcinoma at First Radioablation" include Daniela Schmidt, Attila Szikszai, Rainer Linke, Torsten Kuwert, Clinic of Nuclear Medicine; and Werner Bautz, Institute of Radiology, all from the University of Erlangen-Nürnberg in Erlangen, Germany. JNM, January 2009. |
"The SPECT/CT technology is not as glamorous as PET/CT, so its media coverage has so far been somewhat more limited," said Dr. Kuwert. "It is, however, a very efficient technology. The fusion images speak for themselves."
Dr. Kuwert and colleagues received one of the first SPECT-spiral CT scanners in Europe. After the machine was installed in 2005, the researchers quickly realized its potential and started work in the field of thyroid cancer.
"Now SPECT/CT is a routine tool in our clinic," he said. "Nearly every patient who previously was studied by SPECT now gets SPECT/CT. We experience its enormous advantages in our daily practice and are very enthusiastic about its potential."
Scientific work with SPECT/CT has only just begun, said Dr. Kuwert, with large studies needed to better define the modality's exact role in management of patients with thyroid cancer. He said it is important to recognize that SPECT/CT opens a new window on that disease, offering at least a 30 percent improvement in diagnostic accuracy of metastatic spread of thyroid tumors.
"I feel that some controversies recently raised on the management of thyroid cancer can be very nicely addressed using this technique," said Dr. Kuwert.
Molecular Imaging Viewed as Crucial Worldwide
Progress in molecular imaging has been slow, due in part to the challenges of the biology and also the lack of commercial interest, according to RSNA Science Advisor Daniel C. Sullivan, M.D., a professor of radiology at Duke University Medical Center. High revenue streams are not forecast for these diagnostic agents, especially if they are designed for specific molecular targets, he said.
That said, a number of groups in the U.S., Europe and Asia continue to develop their molecular imaging programs, said Dr. Sullivan. "The goal is to find things like radiopharmaceuticals that are specifically taken up by cancers or other disorders the way thyroid cancer takes up I-131," he said. "Researchers are working on discovering agents that are specific to other cancers.
"For prostate cancer they are working on variations of prostate specific antigen (PSA)," Dr. Sullivan continued. "For lung and breast cancers, they are working on a variety of different chemicals. Some of these are small fragments of antibodies to chemicals and others are compounds that are related to drugs that would be taken up by the cancer to identify where they are and localize them."
Dr. Sullivan, who moderated the Molecular Imaging Symposium at RSNA 2008, said that all major radiology departments worldwide view molecular imaging as a significant part of radiology's future. There won't be a quick change that revolutionizes radiology in just a couple of years, he said, but, gradually over the next five to 15 years, more and more molecular imaging techniques will be optimized and commercialized for use in humans.
"Radiologic and nuclear medical techniques will be moving closer together once again," commented Dr. Kuwert. "I also feel that the trend toward molecular imaging in the field will gain additional strength. Radiologists will experience the clinical attractiveness of molecular imaging, just as we in nuclear medicine have realized that we need the morphological substrate of disease to improve the accuracy of diagnosis."
