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AMSTERDAM -- PET imaging with flurpiridaz F 18, an investigational tracer, provided better image quality and improved diagnostic certainty in coronary artery disease compared with SPECT myocardial perfusion imaging, a phase II trial showed.

The diagnostic performance of PET imaging was also better, as indicated by a greater area under the receiver operating characteristic (ROC) curve (0.82 versus 0.70, P<0.05), according to Jamshid Maddahi, MD, of the University of California at Los Angeles.

There were no serious adverse events reported during the study, he reported at the International Conference of Non-Invasive Cardiovascular Imaging here.

Lantheus Medical Imaging, the sponsor of the study and developer of flurpiridaz F 18, said in a press release that the FDA granted Special Protocol Assessment approval for the agent to move into phase III studies earlier this year.

The phase III program will include two open-label, multicenter trials with a target enrollment of 1,350 patients at about 100 international sites. Coronary angiography will be the gold standard for all patients.

The phase II study was conducted at 21 U.S. sites and included 143 patients who underwent both rest-stress flurpiridaz F 18 PET imaging and technetium-99m-labeled SPECT myocardial perfusion imaging. Stress was induced with either pharmacologic agents or treadmill exercise testing.

For the SPECT images, there was no attenuation correction or processing by ordered subset expectation maximization (OSEM) which is consistent with practice at the majority of U.S. centers, according to Maddahi.

All images were interpreted by three blinded observers.

The subgroup of 86 patients who also underwent conventional coronary angiography served as the basis for data presented by Maddahi, although all of the patients enrolled in the trial contributed safety data.

The mean age of the patients who underwent coronary angiography was 65. Most (60.5%) had significant coronary artery disease (at least 50% stenosis).

A significantly higher percentage of images were rated as good or excellent in the PET group compared with the SPECT group for both stress images (98.8% versus 84.9%) and rest images (95.3% versus 69.8%). Both differences were significant at P<0.01.

In addition, the percentage of images that resulted in an interpretation of definitely normal or definitely abnormal, a measure of diagnostic certainty, was significantly higher with PET (90.7% versus 75.6%, P<0.01).

For the diagnosis of coronary artery disease, sensitivity was significantly higher with PET (78.8% versus 61.5%, P=0.02), but specificity did not differ between PET and SPECT (76.5% versus 73.5%, P>0.05).

Diagnostic performance according to the area under the ROC curve was better with PET.

In terms of safety, there were 100 adverse events in 61 patients, only seven of which were deemed to be possibly related to the study drug. None was serious.

Six of those possibly related to the study drug occurred in one patient, who developed nausea, diarrhea, chest pressure, ST depression, intermittent bradycardia, and cough. Another patient developed hypertension.

There were no clinical laboratory changes from baseline that were reported as adverse events or that were considered clinically significant. Electrocardiographic data at rest showed no evidence of clinically relevant effects on heart rate, PR interval, QRS duration, or repolarization, according to Maddahi.

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