Weil, Christopher R.

Abstract Radiotherapy is an established treatment for low-grade primary cutaneous B-cell lymphoma. Recommendations on its use differ internationally, which prompted our group to conduct this analysis. Twenty-two institutions participated in this international study. Patient eligibility required a diagnosis of limited (T1/T2) primary cutaneous marginal zone or follicle center lymphoma treated with radiotherapy between 1995 and 2023. Data were collected retrospectively until February 2024 within the framework of the International Lymphoma Radiation Oncology Group. Overall, 535 patients were analyzed. Predominant locations were the head (40%) and trunk (36%). Radiotherapy had a median dose of 24 Gy in fractions of 2 Gy. Complete responses were observed in 91% at a median time of 3.6 months following radiotherapy. There was no statistically significant difference between treatments ≤4 Gy and >4 Gy for complete or overall response rates (P = .077 and P = .056, respectively). However, there was an inferior duration of local control with ≤4 Gy (5-year local control 73% ± 12% vs 96% ± 2%; P< .001). Radiation dose was the main prognostic factor in the univariate and multivariable Cox analysis; however, higher doses did not translate into an overall survival benefit. Toxicities rarely exceeded grade 2 but were more frequent in the >4 Gy group. Radiotherapy remains an effective treatment option for indolent skin lymphoma with low toxicity. High response rates are observed with low doses of ≤4 Gy. In comparison to conventional doses, these treatments have a shorter duration of local control but a favorable toxicity profile.

Objective To pool data from prospective clinical trials investigating combined stereotactic ablative radiotherapy (SABR) with immune checkpoint inhibitors (ICI) in patients with metastatic cancers. Methods and analysis PubMed, Scopus and EMBASE were queried for full-length articles of prospective clinical trials involving patients with metastatic solid tumours. Random-effects meta-analysis was performed with the Knapp-Hartung method. Multilevel regression analyses with primary cancers used as random effects and pairwise comparisons with two-tailed test adjusted with Benjamini-Hochberg method were performed. Regression coefficients (β) were calculated to assess the correlation between dose and outcomes. Results We identified 30 trials and 35 individual treatment arms with a total of 951 patients with at least one outcome metric reported. Large heterogeneity was identified for all outcomes measured (I 2 range: 75%–86%). The pooled rate of grade 3+ treatment-related adverse events was 18% (95% CI 11% to 24%). The progression-free survival (PFS) and overall survival (OS) at 6 months were 27% (95% CI 19% to 36%) and 67% (95% CI 59% to 76%), respectively. On multilevel regression, we identified improvement in 6-month PFS (β=0.6, p=0.003) and OS (β=1.6, p=0.04) with increasing BED10Gy doses. Combined-target ICI correlated with better 6-month OS when compared with αPD-1/PD-L1 alone. Conclusion We report a safety profile of combined ICI with SABR in patients with metastatic cancer that is comparable to that of ICI alone. We identified higher doses of radiotherapy and dual-target ICI to be associated with better OS at 6 months. Large heterogeneity and the lack of a control group limit the interpretation of our findings.