Interstitial brachytherapy for orbital soft tissue sarcoma: an innovative technique.

Area of Science:

• Oncology
• Radiation Oncology
• Ophthalmology

Background:

• Orbital soft tissue tumors, such as rhabdomyosarcoma, require precise treatment to ensure efficacy and minimize damage to surrounding ocular structures.
• Traditional external beam radiotherapy (EBRT) poses challenges in dose delivery to the target volume while sparing critical organs at risk.

Purpose of the Study:

• To present an innovative interstitial brachytherapy technique for the treatment of orbital soft tissue tumors.
• To evaluate the safety and efficacy of this technique in a pediatric patient with orbital rhabdomyosarcoma.

Main Methods:

• A 4-month-old child with orbital rhabdomyosarcoma received multiagent chemotherapy and interstitial brachytherapy.
• Pre-planning CT and MRI were used to define the clinical target volume (CTV) and optimize catheter placement.
• Brachytherapy plans were evaluated using dose-volume histograms (DVH) and compared with a RapidArc EBRT plan.

Main Results:

• Interstitial brachytherapy delivered a higher mean CTV dose (158%) compared to RapidArc EBRT (101%).
• While CTV V100 was comparable (90% vs. 95%), brachytherapy significantly reduced mean dose to the lens (51% vs. 60%) and bony orbit (39% vs. 68%).
• A 3-month follow-up MRI showed a complete response of the tumor.

Conclusions:

• This innovative interstitial brachytherapy technique is a safe and effective local treatment for selected orbital soft tissue tumors.
• The technique achieves excellent disease control while significantly reducing radiation dose to surrounding ocular structures compared to EBRT.