Primary malignant giant-cell tumor of bone has high survival rate

Malignant giant-cell tumors (MGCT) comprise 2-9% of all giant-cell tumors (GCTs). The limited existing studies fail to distinguish primary, secondary, or postradiation cancers, making it difficult to design rational treatment strategies. This study compared malignant to benign GCTs and defined the clinical outcome of the patients in a large series of case-matched patients from a single institution.

Clinical, radiological, and outcome features were compared between 26 malignant and 244 benign GCTs treated in our institution. Five postradiation cancers were excluded. We also performed a 1:2 case-matched comparison of patients with malignant and benign disease.

Distal femur (P = 0.019), proximal tibia (P = 0.032), and distal tibia (P = 0.049) had a higher frequency of MGCT. Campanacci stage 1 tumors had a low probability of malignancy (P = 0.017). MGCT were less likely to have aneurysmal bone cyst changes. The 5-year recurrence-free status probability was 80% for malignant and 91% for benign cases in matched groups. The difference in the recurrence rate between benign and malignant groups was not statistically significant (P = 0.24). Functional impairment and limited activity were greater in MGCT patients than in benign GCT patients, whether treated by resection/amputation or curettage/cryosurgery.

We found that malignant and benign GCT have similar epidemiology and that recurrence was higher in MGCT (20 v 9%). Local recurrence for MGCT was not statistically different for excision versus intralesional therapy, but there was little statistical power. Finally, the 16% mortality for patients with MGCT suggests low-grade malignancy.