Low hexokinase-2 expression-associated false-negative ${}^{18}$F-FDG PET/CT as a potential prognostic predictor in patients with multiple myeloma

False-negative ${}^{18}$F-FDG PET/CT, which is associated with low hexokinase-2 (HK2) expression in multiple myeloma (MM), is a new concept that is relevant for diagnosis and treatment response assessment. This study aimed to investigate the prognostic relevance of low HK2 expression-associated false-negative PET/CT in patients with MM. Ninety consecutive patients, with newly diagnosed MM, receiving novel agents during induction therapy were enrolled in this retrospective study. Patients were divided into three groups according to the combination of the positivity of PET/CT and whole-body diffusion-weighted magnetic resonance imaging (DWMRI), namely, negative DWMRI, false-negative PET/CT, and positive PET/CT. False-negative PET/CT was observed in 12% patients who were older, had documented clinical history of smouldering MM, and showed lower HK2 expression levels than the positive PET/CT patients. False-negative PET/CT patients showed a clear trend of longer time to next treatment (TTNT) and progression-free survival (PFS) than the positive PET/CT patients (P = 0.035 and 0.071, respectively). Furthermore, TTNT and PFS of false-negative PET/CT patients were similar to those of patients without established high-risk PET/CT findings and significantly longer than those of high-risk PET/CT patients (P = 0.013 and 0.047, respectively). This study showed, for the first time, that low HK2 expression-associated false-negative PET/CT was associated with relatively better prognosis in patients with newly diagnosed MM, suggesting that this phenomenon may not undermine the established PET/CT-based prognostication. Furthermore, this phenomenon may be useful for identifying patients at lower risk of disease progression among those with myelomatous lesions on DWMRI.