Historically, radioimmunotherapy has been an imperfect fit for treating solid tumors, but a new study published in The Journal of Nuclear Medicine suggests that may be changing.

In a preclinical experiment, a new theranostic approach for treating colorectal cancer achieved a 100 percent cure rate with no toxic side effects.

A research team from Memorial Sloan Kettering Cancer Center and Massachusetts Institute of Technology tested the three-step approach on a mouse model. They focused on an antigen present in over 95 percent of primary and metastatic colorectal cancers in humans called glycoprotein A33.
They targeted GPA33 with a bispecific antibody for A33 tumor antigen and a second antibody for a small-molecule radioactive hapten, which is a complex of lutetium-177 and S-2-(4-aminobenzyl)1,4,7,10-tetraazacyclododecane tetra-acetic acid (177Lu-DOTA-Bn).

Nine mice were randomly selected to undergo the DOTA-pretargeted radioimmunotherapy (PRIT) treatment. SPECT/CT imaging was used to monitor treatment response and measure the amount of radiation absorbed by the tumors.

All of the mice tolerated the treatment well and microscopic exams revealed there was no remaining trace of cancer. There was also no detectable radiation damage to critical organs such as bone marrow and kidneys.

Based on these preliminary findings, the team believes that the anti-GPA33-DOTA-PRIT approach will also be an effective treatment for GPA33-positive colorectal cancer tumors in humans as well as other cancers.

The approach was designed to enable the use of many fine antibodies that target human tumor antigens and it’s applicable to practically every solid and liquid tumor that presents in humans. This has the potential to meet the need for curative treatments for advanced diseases like colon, breast, pancreas, melanoma, lung and esophageal cancer.

Theranostics was a major topic of discussion at this year’s SNMMI annual meeting. A team of Canadian researchers presented their work at the symposium on the use of theranostics to personalized neuroendocrine cancer treatment.

“When we administer treatments in nuclear medicine, contrary to other drugs including chemotherapy and pills, we can see exactly where and how much of our treatment actually goes into organs and tumors by doing a few scans after the administration,” Dr. Jean-Mathieu Beauregard of the Université Laval in Quebec, told HCB News at the meeting.

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