TREATMENT OF REFRACTORY MULTIPLE MYELOMA WITH PSMA-177LU: A CASE REPORT

Introduction/Justification

Triple-refractory multiple myeloma (MM) has a poor prognosis. It is a neoplasm with marked genomic heterogeneity, and recently, our group demonstrated marked uptake of 68Ga-PSMA-11 in some patients, suggesting the potential theranostic use of PSMA in selected cases (1). Herein, we report the initial treatment with 177Lu-PSMA in a patient with refractory MM.

Report

A 76-year-old male patient with IgA/Kappa MM refractory to 6 therapeutic lines, including daratumumab, lenalidomide, and bortezomib, underwent PET/CT with 18F-PSMA-1007, showing marked tracer uptake in multiple osteolytic lesions, several with extensive soft tissue components. A PET/CT with 18F-FDG was also performed, revealing similar findings. A first dose of 7,400 MBq (200 mCi) of 177Lu-PSMA-I&T was administered. The procedure was well tolerated, with slight clinical improvement observed in the week following the infusion. Visual analysis of whole-body scans performed at 21h, 30h, and 7 days demonstrated moderate tracer uptake, lower than that observed with 18F-PSMA-1007. There was slight washout between images at 21h and 30h and moderate/significant washout after 7 days. After 4 weeks, PET/CTs with 18F-PSMA and 18F-FDG were repeated, showing similar findings to the initial scans, with a slight reduction in tracer uptake in some lesions. There was also an increase in the volume of some soft tissue lesions, attributed to post-treatment inflammation. The patient received a second dose of 7,400 MBq (200 mCi) of 177Lu-PSMA-I&T after 6 weeks, and whole-body scans were performed at 2h and 24h, also showing visually lower uptake compared to 18F-PSMA-1007. The patient experienced an intercurrent femoral fracture, limiting mobility for clinical evaluation and subsequent procedures, ultimately leading to their passing after a few days.

Conclusion

This preliminary report suggests that treatment of MM with 177Lu-PSMA is feasible and well tolerated after 2 initial doses. The uptake of 177Lu-PSMA-I&T was visually lower than that of 18F-PSMA-1007, which does not seem to be solely explained by the different resolution of images obtained from different tracers and equipment. There was a slight clinical and imaging response after the first dose, out of a total of 6 planned. A fracture complication and the severity of the case prevented imaging evaluation after the 2nd dose and further treatment continuation. PSMA-177Lu therapy in MM treatment appears to be safe with an initial favorable response, albeit slight. Studies with complete treatments (6 cycles) and in clinically less severe patients are needed to assess the effectiveness of the procedure.