Treatment Outcomes of Low-grade Lymphoma of the Orbit

Radiation therapy can be used with curative intent in patients with low-grade orbital non-Hodgkin's lymphoma (NHL) stages IE and IVE (limited to the bilateral orbits). This study evaluated local control and survival outcomes of patients with unilateral or bilateral orbital lymphoma treated in a provincial population.

The study subjects were 176 patients with low-grade orbital or conjunctival lymphoma referred for management from 1980 to 2016. Demographic, tumour and treatment characteristics were abstracted by chart review. Recurrence-free survival (RFS) and overall survival were assessed with competing risks analysis and Gray's test.

The median follow-up was 8.5 years (range 0.4-29.5 years). The median age at diagnosis was 65 years (range 20-97 years). The most common histological subtype was mucosa-associated lymphoid tissue (MALT) (73%). Stage IVE accounted for 20.5% of the cohort. Orbital radiation therapy was used in 122 patients with stage IE (87%) and 12 patients with stage IVE (28%). The median dose was 25 Gy (range 2-35 Gy). Other treatments were antibiotics (seven patients), chemotherapy (10 patients), radioimmunotherapy (six patients), surgery (three patients) and observation (16 patients). Within the group treated with orbital external beam radiation therapy (EBRT) there were no local recurrences. Among those with stage IE NHL, EBRT was associated with improved local RFS (P ≤ 0.001) but did not have an impact on contralateral or distant RFS. In patients with stage IVE NHL limited to the bilateral orbit, bilateral EBRT was associated with improved RFS (P = 0.012) but did not affect distant recurrences or overall survival.

There were no local recurrences after EBRT for stage IE and IVE orbital low-grade NHL. The treatments offered over the study period varied, but only EBRT for stage IVE disease improved RFS. This supports EBRT as the preferred primary treatment for patients with localised orbital low-grade lymphoma, including those with bilateral disease.