FDG-PET Scans of Lung Nodules Should Be Interpreted With Caution

MedicalResearch.com Interview with:

PET Scan Vanderbilt Health

PET Scan Vanderbilt Health

Amelia W. Maiga, MD MPH
Vanderbilt General Surgery Resident
VA Quality Scholar, TVHS

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: Positron emission tomography (PET) combined with fludeoxyglucose F18 (FDG) is currently recommended for the noninvasive diagnosis of lung nodules suspicious for lung cancer. Our investigation adds to growing evidence that FDG-PET scans should be interpreted with caution in the diagnosis of lung cancer. Misdiagnosis of lung lesions driven by FDG-PET avidity can lead to unnecessary tests and surgeries for patients, along with potentially additional complications and mortality.

To estimate FDG-PET diagnostic accuracy, we conducted a multi-center retrospective cohort study. The seven cohorts originating from Tennessee, Arizona, Massachusetts and Virginia together comprised 1188 nodules, 81 percent of which were malignant. Smaller nodules were missed by FDG-PET imaging. Surprisingly, negative PET scans were also not reliable indicators of the absence of disease, especially in patients with smaller nodules or who are known to have a high probability of lung cancer prior to the FDG-PET test.

Our study supports a previous meta-analyses that found FDG-PET to be less reliable in regions of the country where fungal lung diseases are endemic. The most common fungal lung diseases in the United States are histoplasmosis, coccidioidomycosis and blastomycosis. All three fungi reside in soils. Histoplasmosis and blastomycosis are common across much of the Mississippi, Ohio and Missouri river valleys and coccidioidomycosis is prevalent in the southwestern U.S. These infections generate inflamed nodules in the lungs (granulomas), which can be mistaken for cancerous lesions by imaging.

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ALS Amyotrophic Lateral Sclerosis: FDG-PET as Marker of Cerebral Involvement

Prof. Dr. Philip Van Damme, MD, PhD Neuromuscular Reference Center, Neurology Department, University Hospitals Leuven Vesalius Research Center, VIB, Leuven Leuven Institute of Neurodegenerative Disorders (LIND) KU Leuven, BelgiumMedicalResearch.com Interview with:
Prof. Dr. Philip Van Damme, MD, PhD
Neuromuscular Reference Center, Neurology Department, University Hospitals Leuven
Vesalius Research Center, VIB, Leuven
Leuven Institute of Neurodegenerative Disorders (LIND)
KU Leuven, Belgium

MedicalResearch.com: What are the main findings of the study?

Prof: Van Damme: Earlier FDG-PET studies carried out in the 80’ties already pointed out that patients with ALS had decrease glucose uptake in the brain that is more extended than the motor cortex, at least at the group level. Of course, this imaging technique has been improved since then.

We prospectively assessed the diagnostic and prognostic value of FDG-PET in patients that were referred to us because a diagnosis of ALS was suspected.

The most important finding of our study probably is that FDG-PET shows perirolandic and variable frontotemporal hypometabolism in most patients with ALS at the first presentation in our clinic. It suggests that FDG-PET is a very sensitive marker of cerebral involvement in ALS, which has a high sensitivity at the single patient level.

In addition our study revealed that the co-occurrence of extensive prefrontal or anterior temporal hypometabolism was present in about 10% of patients and had a negative effect on survival after disease onset.
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PET/MRI : A Feasible Modality for Cardiac Imaging

Hybrid PET/MR Imaging of the Heart: Feasibility and Initial Results
Felix Nensa, MD
Department of Diagnostic and Interventional Radiology and Neuroradiology
University Hospital Essen, University of Duisburg-Essen,
Hufelandstrasse 55, 45147 Essen, Germany;

MedicalResearch.com: What are the main findings of the study?

Dr. Nensa: Cardiac positron emission tomography (PET)/magnetic resonance imaging (MRI) with fluorine 18 fluorodeoxyglucose (FDG) turned out to be feasible with an integrated whole-body 3-Tesla PET/MRI system. Despite the presence of a PET detector in the magnetic field of the MR imaging unit, high-quality cardiac MR images were acquired. PET images originating from a PET/CT and the PET/MR scanner showed very good visual agreement and no statistical significant difference of the mean was found in standardized uptake values, however, variance was considerable. In patients with myocardial infarction, PET and MR images were in good concordance regarding both, cine imaging and late gadolinium-enhanced imaging.

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PET scans confirm effectiveness of estrogen-blocking drugs in breast cancer patients

SEATTLE – For the first time, researchers at Seattle Cancer Care Alliance have demonstrated the feasibility of using serial positron emission tomography (PET) scans, using a special estrogen-containing isotope, to confirm the relative effectiveness of estrogen-blocking and estrogen-depleting therapy in patients with metastatic breast cancer. The results of the research are published online in Clinical Cancer Research.

The PET scans, taken before, during and after hormonal therapy, confirmed the superior effectiveness of estrogen-receptor-blocking drugs such as tamoxifen and fulvestrant over estrogen-depleting therapies such as aromatase inhibitors in blocking the estrogen receptor in cancer cells. The study also confirmed that tamoxifen is superior to fulvestrant in blocking estrogen.

While the results were expected they had never before been proven, according to corresponding author Hannah Linden, M.D., a breast oncologist at SCCA and an associate professor of Medicine at the University of Washington School of Medicine.

Linden and colleagues measured regional estrogen-receptor blocking and binding by using PET scans with 18F-flouroestradiol (FES), a trace amount of estrogen in isotope form, prior to and during treatment with aromatase inhibitors, tamoxifen and fulvestrant in a series of 30 patients whose breast cancer had spread to the bones. Tumor FES uptake declined more markedly in patients who took estrogen-receptor blockers compared to those who took estrogen-depleting aromatase inhibitors (an average decline of 54 percent versus 15 percent, respectively). Among the two estrogen-blocking drugs studied, the rate of complete tumor blockade was highest following use of tamoxifen versus fulvestrant.

“What we’re suggesting in the paper — that we couldn’t fully test for before — is if estrogen is incompletely blocked you’re not getting a good outcome for the patient,” Linden said.

“Our findings support the ability of FES PET to visualize the in vivo activity of endocrine therapy,” the authors concluded. “This technology could be used early in drug development to measure effectiveness at the intended therapeutic targets, and to help refine selection and dosing for agents to move forward in drug development.”

Additionally, pharmacodynamic imaging could provide clinicians with a promising tool for therapeutic selection and for predicting and evaluating response to estrogen-receptor-targeted therapy, Linden said.

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The isotope was manufactured by the chemistry group at the UW as part of the UW Nuclear medicine program project grant. Key collaborators in the study include David Mankoff, M.D., Jeanne Link, M.D., and Kenneth Krohn, M.D., at the SCCA, and UW, and Brenda Kurland, a statistician at Fred Hutchinson Cancer Research Center. .

Grants to Linden, Mankoff and Krohn from The National Institutes of Health and the Mary Kay Ash Foundation funded the study.