Hybrid PET/CT enhanced with intravenous CT contrast deserves wider acceptance and adoption, as diagnostically optimized CT can complement PET—and vice versa—for a variety of potential indications.
Not so fast. In too many clinical contexts, the literature to date has shown PET/CT with IV contrast wanting for enough benefits to justify the risks.
That’s the gist of a point/counterpoint debate published as two opinion pieces in the American Journal of Roentgenology May 25.
Point: Contrast-Enhanced Computed Tomography Can Provide Valuable Information in Combination With Positron Emission Tomography
Making the case in favor of IV contrast material for PET/CT, Duke University radiologists Colm Kelleher, MD and Terence Wong, MD, PhD, note the integrated modality’s primary clinical application—oncology [1].
Contrast-enhanced CT, they point out, adds much value to radiologists and oncologists when using PET/CT to characterize primary tumors, evaluate metastatic disease and assess therapy responses.
And that’s only the start. Among other indications Kelleher and Wong name as calling for PET/CT with IV contrast, citing studies to back up each, include detecting and characterizing metastatic lymph nodes, identifying imaging biomarker for predicting lesion-specific therapy response, and finding all disease sites that may be receptor-positive or receptor-negative on concurrent PET scans.
“While IV contrast material is not needed for every PET/CT examination, fully diagnostic CT can provide valuable information in combination with PET and should be used when indicated,” the authors comment. “Patients and physicians benefit from the improved accuracy and confidence provided by a comprehensive PET/CT examination that fully harnesses the synergistic diagnostic capabilities of the CT and PET components.”
Looking ahead, they add, the diagnostic CT component of PET/CT will have “even greater importance” thanks to the arrival of new targeted PET tracers.
Kelleher and Wong conclude:
As we move into an era of personalized medicine, it is crucial that we obtain the most accurate anatomic and functional information possible so that we can make informed treatment decisions for each patient. It is time for us to put the full diagnostic power of CT into PET/CT.”
Counterpoint: Critical Concerns Remain Over IV Contrast Material for PET/CT
In framing their counterpoint [2], radiologists Merissa Zeman, MD, and Esma Akin, MD, of George Washington University Hospital in Washington, D.C., acknowledge that contrast-enhanced CT offers undeniable benefits over unenhanced CT.
But do these benefits carry over into integrated PET/CT studies? And if so, “what must inevitably be sacrificed” to achieve these benefits?
Looking at the prevailing methods for administering IV contrast material for PET/CT, Zeman and Akin state the current approach “inherently contains and propagates errors in attenuation correction and thus metabolic activity.”
Whether these errors are significant is probably the most critical question hanging over the use of IV contrast material for PET/CT.
Further contributing to the downsides, the authors write, are the lack of standardized breathing protocols, the small but real risk of contrast-related adverse events, and the dearth of evidence for clinical benefits to patients in several clinical categories.
The latter subgroup includes patients with lymphoma (particularly those who are post-treatment), patients undergoing active oncologic surveillance with a low index of suspicion for recurrence, patients presenting for a solitary lung nodule, patients with a recent diagnostic CT, and certain patient populations with head and neck malignancies, Zeman and Akin note.
“Recognizing the tradeoffs,” they write, “we now return to the question of whether the benefits of contrast material administration for standalone diagnostic CT extend to integrated PET/CT in a clinically meaningful manner. The answer is: not necessarily.”
Zeman and Akin conclude:
Without a net clinical benefit for the patient, performing a costlier study with increased risks, ranging from increased radiation dose to possible contrast reactions, is not fully justified. As the debate continues over use of IV contrast material for PET/CT, we must first and foremost keep the patient in mind and acknowledge that more is not always better.”
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References:
- Colm Kelleher, Terence Wong, “IV Contrast Material for PET/CT: Point—Putting the CT Into PET/CT.” American Journal of Roentgenology, May 25, 2022. DOI: https://doi.org/10.2214/AJR.22.27793
- Merissa Zeman, Esma Akin, “IV Contrast Material for PET/CT: Counterpoint—Critical Concerns Remain.” American Journal of Roentgenology, May 25, 2022. DOI: https://doi.org/10.2214/AJR.22.27841
Dave P. has worked in journalism, marketing and public relations for more than 30 years, frequently concentrating on hospitals, healthcare technology and Catholic communications. He has also specialized in fundraising communications, ghostwriting for CEOs of local, national and global charities, nonprofits and foundations.