Relapse in patients with limited‐stage ocular adnexal lymphoma treated by chemoimmunotherapy: Extended follow‐up of a phase 2 study

BACKGROUND: Approximately 50% of limited‐stage ocular adnexal mucosa‐associated lymphoid tissue lymphoma (OAML) patients with adverse prognostic factors relapse after radiotherapy. Chemoimmunotherapy has been proposed as an alternative frontline therapy. However, only a few studies have reported its long‐term treatment outcome. METHODS: In 2011, we commenced a phase 2 trial to investigate the efficacy of rituximab, cyclophosphamide, doxorubicin, and prednisolone (R‐CVP) in bilateral and non‐conjunctival limited‐stage OAML patients. Results of the clinical trial showed a response rate of 100% and a 4‐year progression‐free survival of 90.3% without significant toxicity. We extended the study period to December 2020 to determine the long‐term efficacy of R‐CVP chemoimmunotherapy. RESULTS: At a median observation period of 66.0 months, eight of 33 study patients had relapsed. The cumulative incidence of relapse was 18.9% at 5 years and 44.7% at 8 years. The majority of relapses developed more than 4 years after treatment. Local relapse was more prevalent than distant relapse. The relapse risk of orbital and lacrimal diseases was likely to be higher than that of conjunctival and eyelid diseases (HR: 2.5, 95% CI: 0.498–12.500, p = 0.25). CONCLUSION: Although the response rate was remarkable for chemoimmunotherapy, the risk of late relapse was considerable. Based on our findings, clinical trials for limited‐stage OAML patients should have a long‐term observation period. To minimize radiation toxicity and reduce the risk of delayed relapse (local relapse and distant relapse), a future study with sequential or combination treatment of local low‐dose radiation and systemic chemoimmunotherapy can be considered.