New radiopharmaceuticals have been shown to non-invasively identify nearly 30 types of malignant tumors. Called 68Ga-FAPI positron emission tomography/computed tomography (PET/CT), the novel technique was able to indicate a wide variety of cancers with very high image contrast.
Targeting cancer-associated fibroblasts
The 68Ga-FAPI radiotracer works by targeting cancer-associated fibroblasts. These fibroblasts are different from normal fibroblasts and contribute up to 90% of a tumor's mass.
They can be identified by their specific expression of the fibroblast activation protein (FAP). For the study, PET/CTs were used to image 80 patients with unmet diagnoses for 28 different kinds of cancer.
The study found that the tumor-to-background ratios from the 68Ga-FAPI tests resulted in high image contrast and clear tumor delineation. In what is further good news, all patients reported tolerating the examination well.
"The remarkably high uptake of 68Ga-FAPI makes it useful for many cancer types, especially in cases where traditional 18F-FDG PET/CT faces limitations," said Uwe Haberkorn, MD, professor of nuclear medicine at the University Hospital of Heidelberg and the German Cancer Research Center in Heidelberg, Germany.
"For example, low-grade sarcomas generally have a low uptake of 18F-FDG, causing an overlap between benign and malignant lesions. In breast cancer, 18F-FDG PET/CT is commonly used in recurrence, but not generally recommended for initial staging. And for esophageal cancer, 18F-FDG PET/CT often has only a low to moderate sensitivity for lymph node staging."
Better for patients
The test can also be performed without the usual patient preparation required for such examinations such as fasting or recline during uptake time, improving patient comfort. Better yet, the researchers say the approach may even have therapeutic applications some day.
"Cancer associated fibroblasts have been described as immunosuppressive and as conferring resistance to chemotherapy, which makes them attractive targets for combination therapies," Haberkorn said.
"Because the 68Ga-FAPI tracers contain the universal DOTA-chelator, it is possible to label them with therapeutic radionuclides whose half-life fits to the tumor retention time of the carrier molecule. Since the tracer has been observed to accumulate in several important tumor entities, there may be a huge field of therapeutic application to be evaluated in the future."
The research is published in the June issue of The Journal of Nuclear Medicine.