The EOS® System for the Detection of Bone Lesions in Patients with Multiple Myeloma,
Authors: Dutouquet Bastien , Leleu Xavier , Moraux Antoine , Boyle Eileen , Gauthier Jordan , Debarri Houria , Manier Salomon , Noel Marie Pierre , Facon Thierry , Vieillard Marie Helene , Cotten Anne , Boutry Nathalie 
Published: October 2019

Abstract
Abstract 3921

Background.
Osteolytic disease is a major complication of multiple myeloma (MM) that may lead to devastating skeletal-related events (SREs). 70% of patients have osteolytic lesions at diagnosis, and up to 90% develop lytic lesions during the course of their disease. Furthermore, almost 15% of patients present with diffuse osteopenia at diagnosis. Various imaging techniques have been performed for the diagnosis and follow-up of bone disease in MM, however, conventional radiography (CR) remains the gold standard.
CR has several limitations. One is that CR reveals lytic disease when more than 30% of the trabecular bone has been lost. Thus, some patients may have a suboptimal assessment of generalized osteopenia. Another limitation is that CR cannot be used for the assessment of response to therapy because the lytic bone lesions seldom show evidence of healing. On the other hand new vertebral fractures do not always indicate disease progression and may occur due to ongoing bone loss or reduction of tumor mass that supports the bony cortex. Other limitations include lack of accurate visualization of some areas, observer dependency, lengthy period on the examination table, and poor tolerance by patients with severe pain and extended lytic disease.
The EOS System is a new 2D and 3D imaging system for musculo-skeletal physiology and pathology assessment with low radiation dose and standing position. We hypothesized that EOS would not be inferior to CR in terms of routine imaging and diagnosis of bone lytic lesions of patients with MM, but would improve on the quality of life during the procedure of the imaging for the frail patients with MM.

Methods and Materials.
Fifty six consecutive patients with symptomatic MM (at diagnostic and at first relapse) were included in this prospective study. Each patient provided informed consent. All patients underwent an EOS® examination (frontal and lateral views from skull to knees) and radiographs (axial skeleton: skull, spine, pelvis, femurs, humeri, ribs, as per International Myeloma Working Group guidelines) the same day, prior to start any treatment. Each imaging modality was read in random order by 2 reviewers independently for the detection of bone lesions (osteolytic lesions, vertebral collapses). Whole-body MRI was performed in case of disagreement between the 2 imaging modalities. Radiation dose and technical comfort were also assessed. The length of time of either exam was measured and the patients had to fill in a quality of life questionnaire aimed at comparing the roughness of the 2 techniques. Our study received prior approval from our Ethics Committee.

Results.
The median age was 62 (range, 32–90), gender ratio was 30 male / 26 female. CR and EOS® diagnosed 467 and 451 bone lytic lesions, respectively. There was no significant difference between the 2 imaging techniques, as 445 out of 473 bone lesions were detected by both the EOS®system and the CR. The median length of time to perform the CR exam was 6 to 8 times longer than EOS® technique. The average radiation dose with the EOS®system was 7.8 times less than with CR. The majority of the patients found the EOS®system examination to be more comfortable than the multiple radiographic incidences.
The main limitation to EOS® technique was in patients with high BMI greater than 30, in whom CR remains the most sensitive technique. Furthermore, EOS® system was not able to differentiate old versus novel lytic lesions, as expected with standard radiographs. Finally, EOS presented with the same difficulty to count the number of lytic lesions per patient, as for the CR technique.

Conclusion.
EOS® system is a new low-dose radiation device which allows a quicker scan of the whole body. In this preliminary study performed in patients with MM, this technique allowed detection of bone lesions with better comfort for the patients as compared to CR. This is of paramount importance in patients with MM that often presented with altered health status and bone pain that hampered the ability to perform CR with optimal conditions.

Disclosures:
Facon: Celgene: Consultancy, Honoraria; Janssen-Cilag: Consultancy, Honoraria.