Clinical efficacy and safety of proton radiotherapy for ocular conjunctival malignancies: A systematic review and meta-analysis

Tingwei Zheng ¹ Dandan Wang ^2* Yuxin Miao ¹ Meng Dong ^3* Qin Liu ⁴ Qiuning Zhang ⁵ Huiling Bai ^6* Hongtao Luo ^7* Meixuan Li ⁸

• ¹ The First Clinical Medical College, Gansu University of Chinese Medicine, Lanzhou, China
• ² The First School of Clinical Medicine, Lanzhou University, lanzhou, China
• ³ Department of Radiation Oncology, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China
• ⁴ Gansu Provincial Hospital, Lanzhou, Gansu Province, China
• ⁵ Institute of Modern Physics, Chinese Academy of Sciences (CAS), Lanzhou, Gansu Province, China
• ⁶ Gansu Provincial Cancer Hospital, Lanzhou, Gansu Province, China
• ⁷ Gansu Provincial Hospital of TCM, Lanzhou, Gansu Province, China
• ⁸ Evidence-Based Medicine Center, School of Basic Medical Sciences, Lanzhou University, lanzhou, China

Objective: The use of proton beam therapy (PBT) for treating ocular conjunctival malignancies is on the rise across numerous medical centers. This study conducts a systematic review and meta-analysis to assess the effectiveness and safety of PBT in treating malignant conjunctival tumors.Methods: We searched for studies on PBT for ocular conjunctival malignancies in PubMed, Embase, Cochrane Library, and Web of Science (WoS) databases up to November 25, 2023. Studies were selected and data were extracted by two independent reviewers based on pre-established inclusion and exclusion criteria. The quality of evidence was assessed using the GRADE method. Meta-analysis was performed using STATA version 16.0.Results: An initial search yielded 586 articles, from which six retrospective case series studies were selected involving 291 patients with ocular conjunctival malignancies, including 240 cases of conjunctival melanoma and 51 cases of conjunctival squamous cell carcinoma (SCC). Meta-analysis with a random-effects model showed that PBT is effective and relatively safe, with 2-, 4-, and 5-year overall survival (OS) rates of 98% (95% CI 95-102%), 87% (95% CI 69-104%), and 78% (95% CI 70-87%) respectively. Reported toxicity rates included 19% for cataracts, 10% for glaucoma, 5% for lacrimal stenosis, 52% for sicca symptoms, and 11% for limbal stem cell deficiency. The GRADE assessment yielded a low certainty of evidence.Conclusions: Proton therapy offers a viable alternative treatment for patients with conjunctival malignancies, with acceptable treatment-related toxicity rates.