Amino acid PET catches a spectrum of pediatric malignancies

Cancer screening with amino acid PET has already been validated for adults, but it has now been deemed a powerful tool for tumor localization in children and young adults, according to a study published Sept. 19 in the Journal of Nuclear Medicine.

Amino acid PET pinpoints areas of cellular proliferation and makes up for the limitations of mainstay biomarkers like FDG. Researchers including Sebastian M. Harris, MD, from the department of radiological sciences at St. Jude Children’s Research Hospital in Memphis, Tenn., tested the feasibility and biodistribution of C-11 Methionine in a young cohort of patients and found it to be potentially beneficial for imaging growths throughout the head, neck, torso and pelvis as well as in the arms and legs. There were a few limitations, including high background uptake in the upper abdomen especially in the pancreas and liver.

“The high uptake within the pancreas and liver suggests that their background activity may impair the search for neoplasms in the abdomen,” wrote Harris et al. “Relatively low uptake of this agent in brain tissue facilitates tumor localization in the brain. Low background in the neck, chest, and extremities will likely facilitate tumor localization in those regions.”

The methodology included a study group of 93 young patients, 55 male and 38 female, ranging from age 2 to 29 and a median age of 12 with known or suspected neoplasm malignancies. All patients were imaged with C-11 Methionine, and PET and CT and tracer uptake was analyzed for variability according to race, sex and age. Results showed that uptake of C-11 Methionine was especially high in the liver and pancreas, but also high, although less so, in the bone marrow, tonsils and salivary glands. The natural uptick in amino acid use may hinder imaging in these areas. Male subjects showed slightly higher uptake in these organs than females but no significant differences were seen according to race.

PET imaging with C-11 Methionine could be used to augment the screening capability of other biomarkers such as F-18 FDG, which is hampered by high background uptake in the brain and in situations where hypermetabolism could be misdiagnosed for malignancy, including cases of infection and inflammation. FDG is also limited in localizing cancers of the prostate and bladder as well as bronchioloalveolar carcinomas. With further study, pediatric C-11 Methionine PET stands to expand in all of these applications.