PET-CT Theranostic Agent Could Help Detect Pancreatic Tumors

A monoclonal antibody-based improved positron emission tomography/computed tomography (PET/CT) agent could prove useful for diagnosing and treating patients with pancreatic cancer, according to a new study.

Researchers at Memorial Sloan-Kettering Cancer Center (MSKCC; New York, NY, USA) conducted a study to investigate the human monoclonal antibody HuMab-5B1, which targets the cancer antigen CA 19-9. The antigen is expressed on tumors of the pancreas and other malignancies, including small cell lung cancer (SCLC) and tumors of the gastrointestinal (GI) system. For the study, nine patients with metastatic malignancies that were positive for CA 19-9 received four whole-body PET/CT scans, both with and without radiolabeling with zirconium-89. CT scans were performed before the baseline PET/CT to verify the results of the radiotracer.

The first PET/CT scan was performed on the first day of injection with the imaging agent, and again on day two and around days four and seven. The results showed significant tracer uptake in local tumor recurrences, as well as in metastases, with the highest uptake seen on day seven in the lymph nodes. PET/CT scans of HuMab-5B1 radiolabeled with zirconium-89 led to the detection of very small tumors in the peritoneum and mesenteric lymph nodes not seen by CT alone. The study was presented at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) annual meeting, held during June 2017 in Denver (CO, USA).

“This new agent is intensely accumulated in pancreatic cancer and finds very small metastases with PET/CT imaging. What's more, the antibody's high uptake suggests it could be used either by itself or coupled with another molecular compound to treat,” said lead author and study presenter Christian Lohrmann, MD. “There are promising data that HuMab-5B1 could become a theranostic drug used in both targeted imaging and therapy, which could eventually improve the prognosis for pancreatic cancer patients.”

Theranostics use specific biological pathways to acquire diagnostic images and deliver a therapeutic dose of radiation. Once a specific diagnostic test shows a particular molecular target on a tumor, the therapy agent can be specifically targeted to that receptor, providing a more targeted and efficient form of pharmacotherapy.

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Memorial Sloan-Kettering Cancer Center