Which Clinical Factors Are Associated with the Post-Denosumab Size Reduction of Giant Cell Tumors? The Korean Society of Spinal Tumor (KSST) Multicenter Study 2023-02.

BACKGROUND/OBJECTIVES: Denosumab has been considered effective for downstaging giant cell tumor of bone (GCTB), implying that it lowers the Campanacci grade rather than reducing tumor size. Preoperative tumor shrinkage holds therapeutic value by decreasing surgical complications. While previous studies have observed lesion shrinkage in some patients, no study has identified the types of patients likely to show treatment response. Thus, we sought to identify the clinical factors associated with post-denosumab GCTB size reduction.

METHODS

The data for 45 GCTB patients (29 females [64%], 16 males [36%], median age 32 years [range: 17-65]) who received denosumab were analyzed. Lesions were in the extremities ( = 25, 56%) or spinopelvic region ( = 20, 44%). Ten (22%) were recurrent. Lesion size reduction was assessed using two criteria: a ≥5% and a ≥5 mm decrease in the longest diameter. Univariate analyses were conducted for all variables, and those found to be significant were subjected to multivariate analyses. In addition, multicollinearity was evaluated. Subgroup analyses were performed based on lesion location and recurrence status.

RESULTS

Campanacci grade III predicted proportional shrinkage (≥5%) in all patients (OR 4.819, 95% CI 1.121-20.714) and in extremity (OR 11.171, 95% CI 1.023-122.014) and primary lesions (OR 5.781, 95% CI 1.181-28.297), and aneurysmal bone cyst (ABC)-like change was associated with absolute shrinkage (≥5 mm) in all patients (OR 8.734, 95% CI 1.159-65.845) and primary lesions (OR 11.936, 95% CI 1.074-132.69). The longest tumor diameter of ≥7 cm predicted absolute shrinkage in all patients (OR 12.380, 95% CI 1.038-147.694) and for spinopelvic lesions (OR 20, 95% CI 1.676-238.63).

CONCLUSIONS

ABC-like change, Campanacci grade III, and the longest tumor diameter might predict post-denosumab GCTB shrinkage in all patients, though shrinkage varies with lesion location and recurrence status. These factors could help clinicians tailor treatment strategies in different settings. Further research is needed to explore how clinical factors pharmacologically influence denosumab-induced GCTB shrinkage.