Fluorine-18 fluorodeoxyglucose positron emission tomography with computed tomography attenuation correction (PET-CT) in myeloma can detect and enumerate focal lesions by the quantitative characterization of the metabolic activity

A key strategy to improve outcomes in myeloma is to customize the treatment used based on the response to therapy. Such an approach is becoming increasingly feasible as the range of treatment options with different mechanisms of action increases.

The number of tools available to monitor response to therapy is also increasing, with minimal residual disease (MRD) assessment of the bone marrow (BM) using flow cytometry and next-generation sequencing being the most widely used.

The aim of this study was to determine the prognostic significance of the suppression of PET-CT activity at some time points post therapy initiation: day 7, post induction, post-transplant, and at maintenance therapy.

As part of the TT4-6 trial series, 596 patients underwent baseline PET-CT and were evaluated serially during their disease course using peak standardized uptake values above background red marrow signal.

Therapeutic goal

We demonstrate that the presence of more than three focal lesions at presentation identifies a group of patients with adverse progression-free survival and overall survival. At day 7 of therapy, patients with complete focal lesion signal suppression revert to the same prognosis as those with no lesions at diagnosis.

At later time points, the continued suppression of signal remains prognostically important. We conclude that for newly diagnosed patients with focal lesions, treatment until these lesions are suppressed, is an important therapeutic goal as the prognosis of these patients is the same as those without lesions at diagnosis. 

This study suggests that a risk-adapted approach based on serial PET-CT analysis would be appropriate for myeloma patients as it can reliably identify a group of patients with poor prognosis at different stages of their therapy who may benefit from alternative therapy.

On the basis of our results, serial PET-CT should be integrated into follow-up algorithms and risk-adapted clinical trials should be implemented.