Curative radiation therapy for primary orbital lymphoma

Abstract

Purpose: To review our institutional experience with primary orbital lymphoma and determine prognostic factors for survival, local control and distant metastases. In addition, we also analyzed the risk factors for complications in the radiotherapeutic management of this tumor. Materials and Methods: Tumor registry records of 91 patients (pts) with orbital lymphoma from 1973 to 1998 treated at one institution were reviewed. Pts were excluded from the study if they had pseudolymphoma, intraocular lymphoma, metastases to the orbit, palliative radiation therapy or follow-up of less than 6 months. A total of 47 pts with primary orbital lymphoma were treated for cure with radiation therapy. There were 18 males and 29 females with a median age of 69 years (range, 32 to 89 years). Four pts had bilateral involvement. Tumor was located in the eyelid and extraocular muscles in 58%, lacrimal gland 21% and conjunctiva in 21%. Histology was low grade in 68%, intermediate in 30% and high grade in 2%. All pts were stage IAE. Median dose for low grade tumors was 3000 cGy with a range of 2000 – 4020 cGy, while the median dose for intermediate and high grade tumors was 4140 cGy with a range of 3000 – 5100 cGy. Fraction size was 200 cGy in 32 pts, 180 cGy in 14 pts and 170 cGy in 1 patient. Beam energy was 4 MV photons in 62%, 6 MV in 13%, 1.25 MV in 8% and orthovoltage in 2%. Electrons were used in 9% of pts. A single anterior field was employed in 32% pts; the remaining pts were treated with a two field technique that included an anterior and an oblique field or two oblique fields. Pts with bilateral involvement were treated with two lateral fields. Lens sparing technique was used in 34% of pts. None of the pts received chemotherapy for initial management of the tumor. Median follow-up time was 55 months (range 6 to 232 months). Log rank analysis was performed to determine the factors which influenced overall survival and distant metastases. Multivariate logistic regression analysis was employed to determine risk factors for cataract formation and corneal injury. Lens and corneal complications were graded according to objective portion of the SOMA scale of the Late Effects of Normal Tissue (LENT) Scoring System. Results: Local control was 100% in the 51 orbits treated. The overall survival at 5 years was 73.6%. Tumor grade and location within the orbit had no prognostic significance for overall survival or distant metastases. Seven pts developed distant metastases. Sites of metastases included mediastinum, abdomen, extremity and CNS. Cataracts were LENT grade 1 in 8 and grade 2 / 3 in 4 pts. Corneal toxicity was LENT grade 1 in 17 and grade 3 in 1 patient. All pts who had corrective surgery had grade 2 or 3 complications. On multivariate analysis, only male gender predicted for increased risk of cataract formation. Age, radiation dose, fraction size, steroid use and lens sparing technique did not affect the rate of complications. None of the pts who had a lens block had a grade 2 or 3 complication or required surgical correction. Conclusion: Radiation therapy alone is a highly effective modality in the curative management of primary non-Hodgkin’s lymphoma of the orbit. Excellent local control is achievable with radiation doses of 3000 cGy in low-grade and 4000 cGy in intermediate/high grade tumors using conventional fractionation. Although the use of lens sparing technique did not influence cataractogenesis, we continue to recommend lens blocks whenever possible because our experience indicates a higher grade of toxicity and corrective surgery in pts treated without lens sparing technique.