Radiation-induced injury to the visual pathway

Area of Science:

• Ophthalmology
• Radiation Oncology
• Oncology

Background:

• Radiation therapy is a common treatment for nasal cavity and paranasal sinus cancers.
• Visual pathway structures are at risk of injury from radiation treatment.
• Understanding dose-response relationships is crucial for minimizing radiation-induced visual impairment.

Purpose of the Study:

• To review radiation-induced injury to the visual pathway in patients treated for nasal cavity and paranasal sinus cancers.
• To identify factors influencing the incidence and latency of visual impairment.
• To establish dose thresholds for optic neuropathy and chiasm injury.

Main Methods:

• Retrospective cohort study of 219 patients treated between 1969 and 1985.
• Analysis of orbital shielding, treatment plans, and visual acuity follow-up.
• Utilized Cox proportional hazard model and Linear-Quadratic (LQ) model for failure-time data analysis.

Main Results:

• Corneal injury occurred in 24/49 patients treated without orbital shielding, influenced by dose and chemotherapy.
• Symptomatic retinopathy observed in 7/77 patients, with no correlating variables.
• Optic neuropathy (8 patients) and chiasm injury (11 patients) were dose-dependent, with no occurrences below 50 Gy.

Conclusions:

• Total radiation dose is the predominant determinant of visual pathway injury, including optic neuropathy and chiasm injury.
• A threshold of < 50 Gy appears protective against optic neuropathy and chiasm injury.
• Careful dose management and consideration of orbital shielding are essential in radiotherapy for head and neck cancers.