• 6/29/2005
  • Toronto, Ontario, Canada
  • Pippa Wysong
  • Medscape (/www.medscape.com)

The routinely used whole body (WB) positron emission tomography (PET)/computed tomography (CT) scans, also known as limited whole body (LWB), can miss more than 5% of metastatic cancer lesions, according to researchers from Saint Louis University (SLU) who presented their findings here at the Society of Nuclear Medicine 52nd Annual Meeting.

Researchers suggest true whole body (TWB) scans would provide better staging and restaging. That is, scans from head to toe, as opposed to from the base of the skull to about midthigh.

The term “whole body” is somewhat misleading, according to the poster, coauthored by Medhat Osman, MD, from SLU. These scans are done with the patients’ arms up, and the most commonly used field of view does not cover the entire body.

WB scans do not include the brain or the skull, plus it leaves out portions of the upper and lower extremities.

A study was done to see whether performing TWB scans revealed additional lesions above and beyond the traditional approach.

A total of 500 consecutive cancer patients underwent F-18 fluorodeoxyglucose-PET (FDG-PET)/CT scans that extended from the top of the skull to the bottom of their feet. Scans were done 60 minutes after patients received an injection of 0.14 mCi per kg of FDG.

Patients in whom it was already known that malignancies were present outside of the normal LWB area were excluded from the study.

The images were evaluated and newly suspected metastases outside the normal LWB areas were recorded. These newly found lesions in the brain skull and upper or lower extremities were followed up to confirm that they were indeed cancerous.

New lesions were found in 35 (7%) patients, but what the lesions were in two of patients was not confirmed because of a problem with follow-up.

In the remaining 33 patients, five of the lesions yielded false-positive results, whereas metastatic involvement was confirmed in the remaining 28 patients. This gave an overall rate of 5.6% of patients who had metastatic lesions that would have been missed with the traditional WB field of view.

“Of importance, two of the 28 patients had their only metastatic lesion outside the typical WB,” according to the poster.

Doing TWB takes a few minutes longer than the traditional field of view. The researchers are now investigating how the detection of lesions outside the LWB may affect patient treatment.

Patients in the study had a variety of cancers, including lung, melanoma, lymphoma, head and neck, hepatocellular, colon, and more.

It would have been interesting to see more details regarding which new lesions were found in which type of cancer, said Ghassan El-Haddad, MD, a senior nuclear medicine resident at the University of Pennsylvania, Philadelphia. Dr. El-Haddad was not involved in the study.

Dr. El-Haddad points out that TWB is already done in certain types of cancer such as melanoma. He said that “skin metastasis can occur anywhere.” Generally, TWB is not done for cancers such as lung or breast because it is rare that there would be metastases to the toes or hands.

“That is why people do not do it,” Dr. El-Haddad said. He agreed that further studies could elucidate whether TWB would change how physicians manage patients with specific cancers.

There was no commercial support reported for this study.