Current standard RT doses (24-25Gy) provide excellent disease control for patients with indolent B-cell orbital lymphoma, but can cause significant late toxicities. Ultra-low dose RT (4Gy in 2 fractions) has minimal toxicity but lower disease control, requiring intensive follow-up to salvage persistent tumors. Some centers are moving towards this dose as the new standard. A recent study using 12Gy in 4 fractions to any body site showed early data suggesting high disease control rates with minimal toxicity. This study assesses 12Gy in 6 fractions, aiming to enhance disease control over 4Gy while reducing toxicity compared to 24Gy.

Inclusion Criteria:

• Age ≥18 years with stage I-IV indolent NHL*

• Able to provide informed consent

• Histologically confirmed indolent NHL involving one or both orbits. If bilateral, biopsy of only one orbit is permitted as long as high clinical suspicion of contralateral orbit involvement

• Measurable orbital disease after biopsy, either clinically or radiographically

• ECOG performance status 0-3

• Life expectancy >12 months

• Available for treatment and follow-up (including scheduled post-treatment imaging and ophthalmologic exam)

• Able and willing to complete quality of life questionnaires via paper or online portal if they provide their email address on the informed consent document

  • Stage II-IV allowed but if systemic therapy given after RT the timing will be recorded, and subjects will be stratified according to receipt of systemic therapy

Exclusion Criteria:

• Aggressive NHL histology (including grade 3B follicular lymphoma)
• Prior RT to orbit
• Patients requiring treatments outside standard clinical hours
• Systemic therapy for lymphoma is not permitted within the period of time between 2 weeks prior to RT start and 2 weeks after RT completion
• Patients who are pregnant
• History of other malignancy within 5 years prior to screening, with the exception of those with a negligible risk of metastasis or death and/or treated with expected curative outcome (for example, appropriately treated non-melanoma skin cancer, carcinoma in-situ of the cervix, localized prostate cancer, breast ductal carcinoma in-situ, or stage I endometrial cancer)
• Any medical condition that, in the investigator's judgement, would preclude the individual's safe participation in and completion of the study, or could affect interpretation of the results (e.g. pre-existing retinopathy, active connective tissue disease)
• Inability to comply with study and follow-up procedures