Imaging Findings and Value of CT and DCE-MRI in Monitoring Denosumab Therapy of Giant Cell Tumors of Bone

 

Purpose or Learning Objective: Our aim was (1) to evaluate the value of computed tomography (CT) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for monitoring denosumab therapy of giant cell tumor of bone (GCTB); (2) to describe imaging findings at diagnosis and during treatment; and (3) to offer an overview of good and poor response, relapse, and therapeutic complications.

Methods or Background: Twelve patients (eight men, four women; mean age: 33.8 years) with GCTB (four spine, eight limbs) were monitored every 6 months with alternately CT and DCE-MRI (mean follow-up: 4.8 years). Response, relapse, and complications were assessed on imaging studies and semiquantitative measurements.

Results or Findings: On CT, good responders showed progressive reossification of osteolytic areas (mean increase: 12 HU/month), a reduction of tumor volume and soft tissue mass (mean decrease: 0.07 cm³/month), and cortical remodeling. On MRI, first a reduction in contrast enhancement (mean decrease of signal intensity: 55 AU/month), surrounding bone marrow edema (mean decrease of signal intensity: 8 AU/month), and volume were observed. Next, focal necrosis, fatty infiltration, and subsequent progressive reossification and sclerosis of the osteolytic area appeared. On DCE-MRI, the time-intensity curve type evolved gradually from a type IV curve with high first pass, high amplitude, and steep washout rate to an intermediate type III or V curve, and subsequently to a slow type I or II curve. A reduction in wash-in slope, maximum signal intensity, area under the curve, and amplitude of wash-in was observed, together with an increase in arrival time and time to peak. A decrease in Ktrans, initial area under curve, and amplitude A was observed, together with an increase of Ve and Kep (extended Tofts/Brix models).

Patients with poor response or relapse showed the inverse findings of the good responders on CT and DCE-MRI.

Regarding evolution in time, one patient with an initial good response showed a new cortical breakthrough and a new rapidly growing enhancing soft tissue mass with medullary compression and extensive bone marrow edema. Biopsy revealed a highly cellular high-grade conventional osteosarcoma with small interstitial space.

Conclusion: Denosumab is effective in inoperable GCTB and in operable cases with significant morbidity. The evolution of CT and DCE-MRI allows effective continuous monitoring of GCTB and detection of early and late response, relapse, therapy failure, and malignant transformation to osteosarcoma.

Publication History

Article published online:
02 June 2022

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