PET can help guide treatment decisions for neuroblastoma

Children's hospitals in Cincinnati and Memphis have established the value of FDG-PET for depicting the extent of neuroblastoma in some patients, particularly for those in the early stages of the disease.

Findings from the Cincinnati Children's Hospital Medical Center and St. Jude's Children's Research Hospital in Memphis expand the options available for determining optimal therapy for neuroblastoma. The condition accounts for 6% to 10% of all childhood cancers in the U.S. and 15% of cancer deaths in children.

Iodine-123I-metaiodobenzylguanidine (MIBG) SPECT has been the physiological imaging option of choice for assessing the disease. FDG-PET imaging of neuroblastoma is increasing, but questions remain regarding when and in which patients FDG-PET imaging is most useful.

Accurately identifying where in the body the disease is located and whether it is spreading is critical for choosing appropriate treatments, which can include surgery, chemotherapy, radiation, and -- in the most advanced cases -- a combination of all of these along with a bone marrow transplant or investigational therapies.

"Functional imaging plays an important role in assessing neuroblastoma, from initially diagnosing and staging the disease to determining whether patients are responding to treatment or whether the disease has recurred," said Dr. Susan E. Sharp, an assistant professor of clinical radiology at Cincinnati Children's Hospital Medical Center and lead author of the study. "Our study found that while MIBG remains the frontline imaging tool for neuroblastoma, FDG-PET imaging can benefit some patients, especially those with early-stage disease."

The study, published in the August issue of the Journal of Nuclear Medicine (2009;50:1237-1243), also found that FDG-PET may be useful in imaging neuroblastoma tumors that do not readily absorb MIBG. In these cases, imaging with MIBG alone may not reveal some malignant lesions in the body.

Neuroblastoma, a form of cancer that starts in certain types of very primitive developing nerve cells found in an embryo or fetus, occurs most frequently in infants and young children. There are about 650 new cases of the cancer reported in the U.S. each year, according to the National Cancer Institute. The cancer most often originates on the adrenal glands and often spreads to other parts of the body before any symptoms are apparent.

Patients with the disease are classified as low-, medium- or high-risk based on of clinical staging of the disease and certain biologic and genetic characteristics, such as the age of the patient, extent of disease spread, microscopic appearance, and genetic factors.

Treatment varies based on the risk categories. If the cancer is limited to one part of the body, it is often curable with surgery, sometimes with the addition of chemotherapy. But long-term survival for children older than 18 months with advanced disease is poor, despite the various available treatments and combinations of treatments.

The study reviewed a total of 113 paired MIBG scans and FDG-PET scans in 60 patients with neuroblastoma at the two major pediatric cancer institutions.

PET was used in conjunction with localization CT scans, and MIBG planar and SPECT imaging were combined. For stage 1 and stage 2 neuroblastoma patients, FDG-PET depicted more primary or residual neuroblastoma, although MIBG imaging may be needed to exclude higher stage disease that has spread to the bone or bone marrow. MIBG is superior for evaluating stage 4 neuroblastoma, mainly because it can detect and follow the response to treatment of tumor in the bone or bone marrow more accurately.