Making the Choice
With an increasing number of imaging modalities available, choosing the most appropriate one is dependent on several factors, including availability, local expertise, and cost, as well as national guidelines for reimbursement. Because of this, there is currently considerable heterogeneity in which imaging techniques have been incorporated into patient care. To further complicate matters, guidelines issued by international societies including the IMWG, the European Myeloma Network (EMN), the National Comprehensive Cancer Network (NCCN), and the European Society for Medical Oncology (ESMO) all have differences.
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The authors noted that WBLDCT is considered the standard technique for assessing myeloma bone disease because detecting lytic bone lesions is the mainstay for beginning treatment and determining the optimal treatment regimen. WBLDCT is recommended by most guidelines and is routinely implemented in clinical practice. Skeletal survey should be used only in cases when no other imaging modalities are available.
If no signs of bone destruction are detected on CT, then imaging with whole body or axial MRI should be conducted to establish the presence of more than 1 focal lesion, according to the new diagnostic criteria. The authors recommended using PET/CT if there is a strong suspicion of extramedullary disease in patients with oligo-non-secretory MM with normal serum free light chain ratio or in clinical trials including systematic minimal residual disease assessment in order to establish a baseline for response assessment.
The authors also noted that WBLDCT is a good compromise for all other patients.
Patients With Smoldering MM
For patients with smoldering MM, the need for highly sensitive imaging is imperative because this is an early phase of the disease and tumor mass and bone marrow involvement tend to be less pronounced. WBLDCT should be used for all suspected cases of smoldering MM in accordance with IMWG guidelines as identifying lytic lesions will shift the diagnosis into MM. Skeletal survey, as in full blown MM, should only be performed if other techniques are not available.
The consensus statement from the IMWG recommends performing an MRI scan to detect possible focal lesions if WBLDCT does not reveal any sign of bone destruction. Patients with 1 or more unequivocal lesions detected on MRI should be considered as having MM.
Additionally, smoldering MM imaging may be used to identify high-risk patients who are candidates for clinical trials. Aside from having 1 or more equivocal focal lesions, patients may be considered high risk if a diffuse abnormality is found via MRI or if focal FDG uptake is found on PET/CT without evidence of underlying osteolytic bone destruction.
Future Steps
Guidelines from the EMN and ESMO have recommended using WBLDCT to detect lytic bone lesions in MM, MRI to detect bone marrow involvement, and PET/CT for assessment of response to therapy.
However, despite the breadth of imaging modalities now available for diagnosis and treatment of MM, several limitations must be addressed before widespread use of imaging can become feasible, including standardization of guidelines and determination of optimal imaging techniques for different patient subgroups and disease settings.
“Standardization is ongoing for PET and MRI,” explained Dr Zamagni. “Several guidelines from different European and US groups have been published or are ongoing.”
In the review, Dr Zamagni and colleagues concluded that “upcoming prospective trials [that are] extensively applying novel techniques will help address these issues and define the role of these promising tools in clinical practice.”
Reference
1. Zamagni E, Tacchetti P, Cavo M. Imaging in multiple myeloma: Which? When? [published online December 26, 2018]. Blood. doi: 10.1182/blood-2018-08-825256
