CD38 immuno-PET found active myeloma that FDG PET missed in some patients

Design

Prospective phase 2 diagnostic trial

Population

60 people with multiple myeloma

Primary outcome

Disease detection versus FDG PET/CT

Effect

43% vs 47% positive (P = .81); immuno-PET-only active myeloma in 13%

This prospective phase 2 trial enrolled 60 people with multiple myeloma. All had standard FDG PET/CT and bone marrow biopsy, plus research PET/CT with zirconium-89-labelled daratumumab, an antibody targeting CD38. Discordant lesions were biopsied where possible.

Overall detection was similar: immuno-PET was positive in 43% and FDG PET in 47% (P = .81). But in 8 of 60 participants (13%), immuno-PET alone showed disease, and biopsy confirmed active myeloma.

FDG PET can be negative in myeloma with low glycolytic activity. A CD38 tracer may fill part of that gap, but it is a research agent with long-lived zirconium-89 and a multi-day imaging schedule. For now, FDG PET and whole-body MRI remain the clinical tools.

• Remember that a negative FDG PET does not exclude active myeloma
• Consider whole-body MRI where FDG PET is negative but suspicion remains
• Note recent daratumumab therapy when interpreting CD38-directed imaging in trials
• CD38 immuno-PET is investigational and not clinically available

Why it matters

Points to a way of imaging myeloma that does not depend on glucose uptake.

Don't overread it

Phase 2 with 60 participants; it does not show the tracer changes management or outcomes.

The statistics, in plain English

The two scans detected disease in similar proportions overall, so the headline is not that one is better. The finding is that they disagree in some patients, and in eight of sixty the extra disease seen on immuno-PET was real.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.