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CANCER DETECTION AND ASSESSMENT: COMBINED PET-CT IMPROVES ACCURACY IN DIAGNOSIS
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Submitted By: Information, News and Press Releases
Newly combined positron emission tomography (PET) and computed tomography (CT) technology may play a significant role in cancer diagnostics and follow-up, according to studies from three institutions being presented at the 88th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).
PET-CT fusion is a new technology that combines CT’s structural information with PET’s metabolic information into one set of images. Essentially, small lesions are detected with PET and precisely located using CT.
Increasingly, PET is used to detect cancer, assess disease spread and evaluate treatment response. Occasionally, with a PET scan alone the radiologist cannot pinpoint exact tumor location, locate the most active tumor section, or clearly determine tumor status, ranging from malignant to benign. In this instance, follow-up work might include ultrasound, magnetic resonance imaging, biopsy or additional PET. The detailed images that PET-CT fusion provides may decrease the need for additional imaging procedures.
Memorial Sloan-Kettering Study on PET-CT for Head and Neck Malignancies
Combined PET-CT used in head and neck imaging leads to increased confidence in image interpretation, according to a study from Memorial Sloan-Kettering Cancer Center (MSKCC) in New York City.
The study evaluated the clinical usefulness of PET-CT technology in 68 patients with head and neck cancer (156 lesions) by comparing the PET images with PET-CT fusion images.
“We found that combined PET-CT more precisely defined the lesion’s anatomical location in 42 percent (65) of all lesions seen in the regular PET images. Additionally, diagnostic accuracy was improved,” said Heiko Schöder, M.D., assistant attending physician at MSKCC and lead author of the study. “In 56 percent of equivocal PET findings (22 of 39), the additional information from PET-CT fusion images enabled reclassification as either benign or malignant,” Dr. Schöder said.
Dr. Schöder suggested that in the future, combined PET-CT will be the method of choice when PET is performed for staging and follow-up of patients with cancers in the head and neck.
“While it is possible with software programs to attempt fusion of CT and PET images that were obtained at different times, the patient's position is usually not the same in both studies, and changes in tumor size may have occurred in the interval,” Dr. Schöder noted. “Using the PET-CT technology, the physician can navigate through the body and precisely identify abnormalities that were not clearly identifiable by CT or PET imaging alone,” he said.
In a second study, Dr. Schöder and colleagues found PET-CT superior to PET alone when evaluating patients with malignant tumors of the abdomen and pelvis.
Dr. Schöder’s co-authors on the studies are Henry W. Yeung, M.D., and Steven M. Larson, M.D.
Johns Hopkins Study Finds PET-CT Detects Ovarian Cancer Metastases
PET-CT is also highly effective in diagnosing ovarian cancer, according to a study from the Johns Hopkins Medical Institutions (JHMI) in Baltimore. The study investigated the sensitivity and specificity of PET and PET-CT for abdominal spread of ovarian cancer.
“PET-CT is adding to our diagnostic certainty, as well as our certainty in locating the lesions and separating them from normal tissue,” said the study’s co-author, Richard L. Wahl, M.D., the Henry N. Wagner Jr. professor of nuclear medicine, director of the division of nuclear medicine and vice-chairman of radiology at JHMI.
For the study, 10 PET and 33 PET-CT examinations were performed on 28 patients. The study found that PET alone had a sensitivity of 100 percent and a specificity of 50 percent, while combined PET-CT studies had sensitivity of 73.6 percent and a specificity of 100 percent. In 25 of the 33 PET-CT scans, the PET and CT portions were congruent. The findings indicated that PET-CT appeared to increase the specificity for detecting peritoneal metastases from ovarian cancer over PET alone, and that PET-CT had high overall diagnostic accuracy.
“The best imaging study we can do for the detection of ovarian cancer is PET-CT, which has a very high sensitivity for detecting disease and is very specific,” said co-author Elliot K. Fishman, M.D., professor of radiology and oncology and director of diagnostic imaging and body CT at the Sidney Kimmel Comprehensive Cancer Center at JHMI. “However, physicians should not solely rely on PET-CT to detect metastases,” he said, adding that some lesions may be seen only with contrast-enhanced CT.
Drs. Wahl and Fishman contributed to a second JHMI study being presented at the RSNA meeting that found combined PET-CT imaging more accurate than PET alone in the
detection of suspected recurrence of colorectal cancer.
Co-authoring the ovarian cancer study with Drs. Wahl and Fishman are lead author Harpreet K. Pannu, M.D., Robert Bristow, M.D., and Fredrick J. Montz, M.D.
Co-authoring the colorectal cancer study with Drs. Wahl and Fishman are lead author
Ihab R. Kamel, M.D., Ph.D., Christian Cohade, M.D., Medhat M. Osman, M.D., Ph.D., and Edward G. Neyman, M.D.
University Hospital—Zurich Study Uses PET-CT to Detect Lung Cancer
Integrated PET-CT imaging is superior to all other imaging methods in the detection of tumors in patients with lung cancer, according to a study from University Hospital in Zurich, Switzerland.
“Combined PET-CT precisely identifies and localizes even small metastases, thus avoiding further examinations,” said lead author Hans C. Steinert, M.D., assistant director of nuclear medicine at University Hospital. “Additionally, PET-CT’s precise results help physicians plan more exact treatment.”
The study evaluated integrated PET-CT compared to conventional imaging to determine if there were additional findings in preoperative staging of non-small-cell lung cancer (NSCLC). The study found that combined PET-CT improves preoperative staging of lung cancer, resulting in a change in therapy for 1 in 4 patients.
PET looks for “hot spots,” which can represent abnormal cell growth. Combined PET-CT precisely locates the PET hot spot anatomically on CT. “In patients with a newly diagnosed NSCLC, we strongly recommend combined PET-CT for preoperative staging,” Dr. Steinert said. “Due to the exact localization of the hot spots, oncologists can better plan efficient treatment.”
Dr. Steinert believes that in the near future, when integrated PET-CT systems are more readily available, it will become the new standard imaging modality in oncology.
Media Contacts: Maureen Morley or Doug Dusik (312) 791-6667
Before 11/30/02 or after 12/6/02: Maureen Morley Doug Dusik
(630) 590-7754 (630) 571-7845
mmorley@rsna.org ddusik@rsna.org
Dr. Steinert’s co-authors are Didier Lardinois, M.D., Thomas F. Hany, M.D., Burkhardt Seifert, Ph.D., Walter Weder, M.D., and Gustav K. Von Schulthess, M.D., Ph.D.
H. William Strauss, M.D., clinical director, nuclear medicine service at Memorial Sloan-Kettering Cancer Center in New York will moderate the PET-CT press conference.
The RSNA is an association of more than 33,000 radiologists, radiation oncologists and physicists in medicine dedicated to education and research in the science of radiology. The Society’s headquarters are located at 820 Jorie Blvd., Oak Brook, Ill. 60523-2251.
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