Association between rheumatoid arthritis and risk of radiotherapy toxicity: a systematic review.

Objective: There is sometimes concern over the use of radiotherapy for cancer in individuals with rheumatoid arthritis (RA), but little evidence to support its avoidance. Identifying any association between RA and risk of radiotherapy toxicity could impact current guidance. We aimed to review the evidence base. Methods and analysis: Following PRISMA 2020 guidelines, a systematic review was conducted of Medline, Embase and PubMed databases on 25 November 2019 and updated 22 February 2024. Articles identified for inclusion were reviewed by two independent assessors. Results: 155 articles were identified. With repeat articles excluded, 114 remained. 12 articles were included in qualitative analysis. Six studies held no comparison cohort; one compared RA to non-RA collagen vascular disease (CVD) patients; five compared patients with RA to CVD or a matched pair. Studies showed patients with RA developed higher levels of toxicity however only two studies had statistically significant results. Nine of the 12 studies had medium to low quality evidence and displayed predisposition to numerous biases. Conclusion: Due to limited high-quality research, it is difficult to draw a clear conclusion on the relationship between RA and radiotherapy toxicity. Given the current lack of strong and high-quality evidence identified in this review, dose reduction of radiotherapy in patients with RA lacks sufficient evidence to be recommended. There is a need for further high-quality research involving prospective analyses of toxicity, up-to-date radiotherapy techniques, long follow-up, and large cohorts. Also, analyses need to adjust for confounding factors, match for risk factors, and incorporate RA activity status assessments.