Dynamic Metabolic Changes during the First 3 Months after 90Y-Ibritumomab Tiuxetan Radioimmunotherapy

Abstract EN

Objective.

To elucidate the time course of tumor metabolism during the first 3 months after 90Y-ibritumomab tiuxetan radioimmunotherapy (RIT) in patients with refractory malignant lymphoma.

Materials and Methods.

Seven patients with recurrent follicular lymphoma underwent FDG-PET imaging before and after 1-, 4-, and 12-week RIT with 90Y-ibritumomab tiuxetan.

Tumor metabolic activity on FDG-PET scans was assessed as the maximum standard uptake value (SUVmax).

Results.

Decrease in metabolism was detected 1 week after RIT.

In the most decreased lesion, SUVmax decreased to 20% of the baseline value during the first week.

Most lesions continued to decrease for up to 4 weeks.

Some lesions showed increased metabolism from 4 to 12 weeks, while the level of FDG accumulations at 12 weeks was still lower than the baseline.

Conclusions.

Tumor response to RIT could be observed as early as 1 week after the administration of RIT.

After tumor activity decreases, the metabolism may increase at least between 4 and 12 weeks.

It suggests that the metabolic changes should be carefully evaluated during this period.