Contrast-induced changes in chemical exchange saturation transfer MRI differentiate tumor progression from...

Area of Science:

• Oncology
• Medical Imaging
• Immunotherapy

Background:

• Tumor pseudo-progression (PsP) mimics true progression, often leading to premature treatment cessation.
• Distinguishing PsP from true progression is crucial for effective cancer treatment.
• Current imaging methods struggle to differentiate inflammatory infiltrates from viable tumor cells.

Purpose of the Study:

• To explore gadoterate meglumine (Gd-DOTA) and amine-CEST imaging for differentiating tumor from radiation necrosis.
• To assess Gd-DOTA uptake by infiltrating immune cells, like macrophages, using amine-CEST.
• To develop a non-invasive imaging biomarker for PsP and treatment response monitoring.

Main Methods:

• Incubation of F98 cancer cells and macrophages with Gd-DOTA.
• Amine-CEST imaging on a 9.4 Tesla preclinical scanner.
• In vivo amine-CEST imaging in F98 tumor-bearing and radiation necrotic rats post-Gd-DOTA injection.

Main Results:

• Macrophages showed a ~40% decrease in amine-CEST signal after Gd-DOTA uptake, indicating T1 shortening.
• Cancer cells did not show significant changes in amine-CEST signal, indicating no Gd-DOTA uptake.
• In vivo studies revealed decreased amine-CEST contrast in radiation necrotic rats (macrophage uptake) but not in tumor-bearing rats (no cancer cell uptake).

Conclusions:

• Amine-CEST imaging combined with Gd-DOTA can differentiate macrophages from cancer cells based on Gd-DOTA uptake.
• This method shows promise for non-invasively characterizing pseudo-progressive lesions.
• The approach could aid in monitoring treatment responses and optimizing cancer patient management.