Applied Radiology

The Society of Nuclear Medicine (SNM) held its annual meeting from June 1st to June 5th in San Antonio, Texas, where leading clinical investigators presented evidence to support the expanding role of nuclear medicine in oncology and cardiology. In addition, several cost-effectiveness studies showed that tests once considered "too expensive," such as positron emission tomography (PET), can actually save money.

Four new radiopharmaceuticals, launched in 1997, show that the commercial sector supports the growing field of nuclear oncology.

1. Technetium-99m sestamibi (Miraluma™, DuPont Merck) is now available for radionuclide breast imaging, or scintimammography. This is the same radiopharmaceutical kit that is marketed under the brand name Cardiolite® for myocardial perfusion imaging.

2. Samarium-153 lexidronam (Quadramet®, Cytogen/

DuPont Merck), a radionuclide therapy for bone pain, concentrates in regions of bone invaded by metastatic tumors. Because samarium-153 emits both beta particles (therapeutic) and gamma rays (diagnostic), its uptake can be imaged with gamma cameras.

3. Technetium-99m nofetumomab (Verluma™, DuPont Merck) is a new radiopharmaceutical for disease staging in patients with biopsy-confirmed, previously untreated small-cell lung cancer.

4. Indium-111 capromab (ProstaScint®, Cytogen/Bard) is a new kit for imaging patients with prostate cancer.

Scintimammography multicenter trial

A multicenter clinical trial in Europe, which enrolled 246 patients with suspicious breast lumps or mammograms, found that scintimammography was able to diagnose malignant breast tumors in 60% of patients who had false-negative x-ray mammograms (abstract #67). [Abstracts are published in J Nucl Med 39:3P-311P, May 1997.] Scintimammography "can contribute significantly to the clinical workup of patients with suspected breast cancer," according to researchers from the University of Bonn, Germany, who presented the European data here.

"I do not see any situation where scintimammography would replace mammography," said Holger Palmedo, MD, of the Department of Nuclear Medicine at the University of Bonn. Younger women (under age 50) with dense glandular breast tissue could benefit most from scintimammography, particularly a patient with a palpable mass and a normal mammogram. "ln this group of patients, mammographically dense breast tissue can result in delayed diagnosis of breast cancer. Scintimammography can help to detect additional cancers in this group of symptomatic patients," said Dr. Palmedo. In addition, scintimammography is useful for women with breast implants, who cannot have their breasts compressed in mammography imaging equipment.

Staging lung cancer

Technetium-99m nofetumomab, the new radiopharmaceutical kit for staging lung cancer, could eliminate the need for an entire battery of traditional tests now used to stage these patients. PET imaging with fluorine-18 fluorodeoxyglucose (FDG) is also proving itself as a clinical lung-cancer staging tool. Fluorine-18 FDG is now available in several areas of the country through P.E.T.Net™ Pharmaceutical Services™, a network of positron distribution centers with headquarters in Norcross, Georgia.

"When there is histological proof of lung cancer, PET is helpful for staging patients," said Dr. Yeung. PET often "upstages" patients, showing metastatic cancer that went undetected by CT or other imaging tests, thereby eliminating surgery as a practical treatment option. Sometimes, PET "downstages" patients. "When CT identifies enlarged lymph nodes, it's usually cancer. But sometimes, the lymph node is enlarged for other reasons, such as scar tissue from a previous fungal infection," noted Dr. Yeung. In such cases, the PET scan would be negative, and the patient's cancer staging might go down enough to make surgery a reasonable option (abstract #292).

Nuclear medicine physicians at the Saint Louis University Health Sciences Center measured how often PET would have correctly altered staging, when compared with CT, in patients with non-small cell lung cancer (abstract #293). They retrospectively compared PET and CT results with the surgical pathology reports of 52 patients. PET and CT were similar in sensitivity (88%), the ability to detect disease when it is present. However, PET was much better than CT in specificity (75% vs 54%, respectively), the ability to rule out disease accurately when it is not there. Overall, the accuracy of PET in predicting which patients had resectable lung cancer was 78%, compared with a 63% accuracy for CT.

Detecting metastatic prostate cancer

Nuclear medicine departments that want to offer indium-111 capromab tests must be certified by the American College of Nuclear Physicians (ACNP). Cytogen established this certification program to ensure that nuclear medicine departments are thoroughly educated in how to use indium-111 capromab and interpret the images. So far, the ACNP has certified more than 120 sites in the United States.

So that the SPECT image from patients with prostate cancer can be fused with x-ray computed tomography (CT) studies, investigators at the University of Illinois have developed a dual-isotope imaging procedure using indium-111 capromab and technetium-99m-labeled red blood cells (abstracts #509 and #986). This method for three-dimensional registration of SPECT and CT increased lesion detection by 59% in 23 patients, and most unsuspected lesions were found in the pelvis, according to Michael J. Blend, MD, head of nuclear medicine.

Cost savings with PET: $4,300 per patient

A retrospective comparison of 64 patients with suspected recurrent colorectal cancer indicated that whole-body FDG-PET provides a more cost-effective staging tool than CT (abstract #334). These patients were thought to have resectable tumors, based on CT results, before they were evaluated with PET. Results of FDG-PET studies indicated that 22 (34%) of these patients actually had nonresectable tumors. Avoiding surgery in these patients would reduce health care costs by a substantial amount. When the cost impact of PET ($1,800 per scan) was calculated, the research team determined a net savings-to-cost ratio of more than 4 to 1, and a cost savings of approximately $4,300 per patient.

The SNM recently published a booklet, "Clinical Nuclear Oncology," which included five cost-effectiveness studies. In addition to whole-body FDG-PET for staging lung and colorectal cancers, these studies covered the pharmacoeconomic benefits of strontium-89 therapy, a cost-effective imaging work-up for hepatic hemangiomas, and a report on somatostatin receptor scintigraphy.

Myocardial perfusion SPECT in ER saves $3.5 million/year, $1,900/patient

To study the cost impact of myocardial perfusion single-photon emission computed tomography (SPECT) in patients with chest pain, researchers from the Chest Pain Center at Baptist Hospital of Miami and the Miami Cardiac & Vascular Institute decided to offer this nuclear medicine test 24 hours/day, 7 days/week, on an emergency basis (abstract #492).

"Myocardial perfusion imaging, coupled with stress testing when indicated, can provide rapid and decisive data to effectively triage patients with chest pain, whether the pain is ongoing or resolved," said Jack A. Ziffer, PhD, MD, director of cardiac imaging at the Miami Cardiac & Vascular Institute, and director of nuclear medicine and PET at Baptist Hospital.

The estimated cost savings from avoiding hospital admission in patients who were unlikely to have future cardiac events amounted to $3.5 million/year, or $1,900/patient. Estimates were based on patients' charges for routine evaluation in the chest-pain center compared with inpatient charges for comparable evaluation.

Over an 18-month period, Dr. Ziffer and colleagues evaluated 4,820 patients at their chest-pain center, a dedicated 8-bed facility. A subset of 2,737 patients underwent myocardial perfusion imaging, and 77% of these patients were discharged without hospital admission. The mean length-of-stay in the chest-pain center was 12.2 hours (0.5 days), compared with 45.6 hours (1.9 days) when patients were admitted. Myocardial perfusion SPECT results were made available quickly, about 1.5 hours after the patient was injected with the radiotracer. Among the 2,086 patients discharged as outpatients, there are only 2 known myocardial infarctions (one 2 days after discharge, and one 3 months after discharge).

Computer-controlled drug-delivery myocardial perfusion stress tests

A new drug-delivery device for myocardial perfusion stress imaging, the GenESA® System (Gensia Sicor Inc.), will soon be available in the United States (abstract #266). The system holds a syringe of arbutamine, a drug that stresses the heart for patients unable to exercise, and continuously controls and adjusts the infusion of the drug according to how fast the physician wants the patient's heart beat to accelerate, and also according to how the patient's heart rate and blood pressure change in response to arbutamine (figure 1).

"Because of arbutamine's mechanism of action, simulating the cardiac effects of exercise, and the convenient control features provided by the GenESA infusion device, I expect this drug to have significant use in the diagnosis of coronary artery disease using radionuclide perfusion imaging," said Daniel S. Berman, MD, director of nuclear cardiology at Cedars-Sinai Medical Center in Los Angeles. The GenESA System is also designed for stress echocardiography.

Unlike dipyridamole and adenosine, pharmacologic stressors that dilate coronary arteries, drugs such as arbutamine and dobutamine, more closely simulate the hemodynamic response to exercise by increasing heart rate, cardiac contractility, and systolic blood pressure. The patient is connected to the GenESA System with electrocardiographic (ECG) and blood-pressure devices, which monitor the patient during infusion. The computer uses ECG and blood-pressure data to control the rate of arbutamine infusion.

Myocardial perfusion imaging: A sophisticated prognostic tool

Myocardial perfusion imaging is becoming a highly sophisticated tool for predicting future events in various types of cardiac patients. Cardiovascular nuclear medicine physicians at Cedars-Sinai Medical Center in Los Angeles presented data from several large-scale studies showing that myocardial perfusion imaging can predict:

• Which diabetic patients with coronary artery disease are most likely to experience future myocardial infarction (MI) or cardiac death (abstract #142)

• Which patients are most at risk for revascularization, MI, and cardiac death following percutaneous transluminal angioplasty (PTCA) (abstract #487)

• Which patients are at risk of cardiac death at five or more years after coronary artery bypass graft (CABG) surgery (abstract #143)

Led by Dr. Berman, the Cedars-Sinai group uses a special scoring method to categorize radiotracer activity in myocardial perfusion scans. Scores for 20 myocardial segments are used to calculate the "summed stress score," or SSS. SPECT scans with an SSS greater than 8 are considered to be moderately to severely abnormal, and those patients may be candidates for more aggressive work-up and treatment.

Determining a patient's risk for MI or cardiac death can help determine treatment strategies. For example, revascularization only lowers the risk of cardiac death, not MI. Therefore, patients at lower risk for cardiac death and higher risk for MI may benefit more from medical therapies than from angioplasty or bypass surgery.

Interactive CD-ROM accredited

for CME and VOICE

UNM, Ltd., an Illinois corporation that produces continuing medical education (CME) materials, exhibited a new interactive CD-ROM, "Technical Challenges in Nuclear Medicine." It's the first computer-based program to be awarded CME credit by the SNM, and one of the few programs that offers both CME and VOICE (for nuclear medicine technologists) credits. Volume 1, available now, covers standard gamma camera evaluation.

Future volumes will cover quality control, radiopharmaceuticals, and high-energy imaging.

"In the face of pressures from managed care and other agencies, quality may fall by the wayside," said Robert E. Henkin, MD, president of UNM, Ltd. "Continuing medical education is vital to the maintenance of good patient outcomes. It is UNM's intention to continue to make available to the community programs that permit practitioners to maintain and enhance their skills by utilizing modern technology for education," said Dr. Henkin. The CD-ROM operates on Windows 3.11, 95, and NT.

Equipment manufacturers:

Partners or competitors?

Some odd business relationships have developed among major equipment manufacturers, blurring the lines between competing product groups.

The Siemens E.CAM™, a dual-detector, variable-angle gamma camera, now "rounds-out Toshiba's nuclear medicine product line," according to Toshiba. Siemens and Toshiba signed an agreement that allows Toshiba, on a nonexclusive basis, to supply and service the E.CAM worldwide.

GE Medical Systems and Elscint Ltd. have formed a joint venture, named ELGEMS Ltd., which plans to start operating in Haifa, Israel, this month. ELGEMS will develop and manufacture nuclear medicine equipment that both GE and EIscint will sell under their own brand names in the United States.