398P - Evaluation of the effectiveness of denosumab therapy giant cell tumor of the pelvis

Background

Giant cell tumors of the pelvis and sacrum most often occur in people of working age, which determines the high social significance of successful treatment of this category of patients. Surgery of GCT in sacrum and pelvis is challenging, with high rates of complications and local recurrence. Denosumab can consolidate the peripheral rim of the tumour, thus reducing the rate of morbidities of surgery. The aim of this study is to evaluate the use of denosumab in long cell tumors of the pelvis and sacrum (GCT).

Methods

We retrospectively reviewed a cohort of 19 patients with GCT in sacrum or pelvis treated with denosumab at at the Republican Cancer Center. Clinical response and local recurrence were recorded and the radiologic responses were evaluated with the MDA criteria.

Results

Before treatment, the extraosseous component was determined in 57.9% (n = 11), after treatment – in 31.6% (n = 6). The decrease occurred in 100%, the disappearance - in 45% (n = 11) of cases. The thickness of the extraosseous component before treatment ranged from 4 to 43 mm (Me = 15 mm), after treatment it ranged from 0 to 30 mm (Me = 8 mm). The decrease occurred in the range from 4 to 14 mm (M ± SD = 7 ± 4 mm). In 100% of cases, a sclerotic rim appeared, the thickness of which after treatment ranged from 1 to 5 mm (Me = 3 mm). In the structure of the tumor, fibrosis occurred in 95% (n = 18), a decrease in the cystic component occurred in 82% (n = 9) of cases. Perifocal changes decreased in 100% of cases. In 100%, the average density of the tumor increased. The mean tumor density before treatment ranged from 27 to 65 HU (M ± SD = 42 ± 11 HU), after treatment it ranged from 69 to 500 HU (Me = 150 HU). The increase in density occurred in the range from 41 to 454 HU (Me = 101 HU). All differences are statistically significant (p < 0.05).

Conclusions

Long-term denosumab therapy can be considered with curative intent for pelvic and sacrum GCTB. If surgical intervention is required wide resection may be advisable to reduce the risk of recurrence.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

A.I. Nurjabov

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.