An International, Multi-Centre Study of Radiotherapy for Bilateral Indolent Orbital Adnexal Lymphomas (IOAL).

Purpose/objective(s) Radiotherapy is curative for the majority of patients with IOAL. Some reports suggest inferior outcomes for bilateral IOAL, leading to uncertainty regarding optimal management for this presentation. This retrospective, international study evaluated long-term outcomes of bilateral IOAL treated with radiotherapy alone, with the current analysis limited to synchronous presentations (defined as ≤90 days between diagnoses). Materials/methods Ninety patients with bilateral synchronous IOAL were treated with radiotherapy to both orbits at 13 centers. Overall (OS), progression-free survival (PFS), freedom from local (FFLF) and freedom from distant (FFDF) failure were measured from the commencement of treatment of the second orbit. The study met local institutional review board requirements. Results The median age at diagnosis was 55 years (range 15-83), with 47% males. Histology was marginal zone lymphoma in 90% and disease was conjunctival in 65% of orbits. Sixty-three percent had bilateral conjunctival disease. The radiotherapy dose (per orbit) was 20-25.2 Gy for 46%, 27-30.6 Gy for 33%, 33-40 Gy for 8% and 13% had 4 Gy. Radiotherapy was given to the whole orbit for 62% of orbits, conjunctiva only for 29% and other partial orbit for 9%. Median follow-up was 6.6 years. The 10-year OS and PFS were 99% (95% CI: 92-100) and 73% (95% CI: 60-82), respectively. Ten-year FFLF and FFDF were 88% (95% CI: 78-94) and 83% (95% CI: 70-91), respectively. PFS was lower for the 33 patients with one or both orbits having non-conjunctival disease (HR 3.7 (1.4-9.3), P = 0.004). Three-year FFLP was 91% (95% CI: 81-95) for orbits receiving ≥ 20 Gy and 61% (95% CI: 27-84) after 4Gy (P Conclusion In this large, multicenter experience, patients with bilateral, synchronous IOAL treated with radiotherapy alone appeared to have outcomes comparable to historical series of unilateral disease. These results would suggest bilateral IOAL can be considered a localized process and support the use of curative intent radiotherapy in this setting.