Purpose

To demonstrate the role of radiotherapy and quantify treatment response in an orbital solitary fibrous tumour (SFT) using volumetric imaging analysis.

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Methods

Single-case analysis with serial imaging before and after radiotherapy. Tumour volume was calculated using 3D reconstruction with 3D Slicer software.

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Results

A 60-year-old female presented with a four-year history of progressive proptosis. Examination demonstrated 8 mm of right proptosis with hypoglobus. Axial CT imaging revealed a well-circumscribed, heterogeneous superotemporal intraconal mass. Incisional biopsy confirmed solitary fibrous tumour with moderate mitotic activity (8/10 high-power fields) and no necrosis. The patient declined further surgery and underwent radiotherapy (total dose 44 Gy). Serial imaging at four time points demonstrated progressive tumour regression over three years, with volumetric analysis confirming a 73.1% reduction in tumour size. Reduction was initially rapid in the first year (≈ 0.18 cm3/month) and was gradual over the next two years (≈ 0.03cm3/month). This was accompanied by marked improvement in proptosis and preservation of normal visual function.

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Conclusion

Radiotherapy may result in significant tumour reduction in orbital SFT when complete excision is not feasible. Volumetric analysis provides an objective, reproducible method for assessing treatment response and may support standardisation of outcome reporting.

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Additional Authors

First name	Last name	Base Hospital / Institution
Kaveh	Vahdani	Moorfields Eye Hospital
David	Verity	Moorfields Eye Hospital

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