Ultra Low Dose Orbital Radiation Therapy in Treating Patients With Stage I-IV Indolent B-cell Lymphoma or Mantle Cell Lymphoma

Inclusion Criteria: * Patients 18 years or older with stage I-IV indolent B cell lymphoma, including MALT and follicular grade I/II. Patients with mantle cell lymphoma will also be included in this study, as mantle cell lymphoma is also radiosensitive, despite it not being an indolent B cell lymphoma. Patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) are ineligible. * Patients must have measurable disease within the orbit, either clinically and/or radiographically after biopsy confirmation of B cell lymphoma. * Bilateral ocular adnexal involvement is permitted, if biopsy confirms unilateral disease and there is high clinical suspicion for bilateral disease, biopsy of the contralateral ocular adnexa can be waived. * Female patients of childbearing potential must have a negative serum pregnancy test (βhCG) within 2 weeks of protocol entry. * Planned systemic therapy after orbital radiation therapy is permitted however the timing of systemic therapy will be recorded and patients will be stratified according to receipt of adjuvant systemic therapy. * Male patients must agree to use a barrier method of contraception or agree to abstain from heterosexual activity for the duration of the study. * Female patients must be willing to use two adequate barrier methods of contraception to prevent pregnancy or agree to abstain from heterosexual activity throughout the study or be post-menopausal (free from menses \> two years or surgically sterilized). * Pati…