Particle Beam Therapy Tolerance and Outcome on Patients with Autoimmune Diseases: A Single Institution Matched Case–Control Study

SIMPLE SUMMARY: The decision to offer radiation therapy for cancer in patients with autoimmune diseases is problematic, due to the possibility that such diseases can predispose patients to higher acute and late treatment toxicity by triggering a pro-inflammatory cascade. Specifically, no data are available regarding the impact of this problem on particle therapy. Although the number of patients who access particle therapy is lower than photon treatment, and despite the fact that autoimmune diseases are not a frequent comorbidity in the population, our study reports an increase in terms of acute G3 toxicity in patients with autoimmune diseases compared to a control group without ADs. Since no severe G4–G5 events were reported and in consideration of the benefit of particle therapy for selected cancers, we conclude that article therapy should be not discouraged for patients with autoimmune conditions. ABSTRACT: It is unclear whether autoimmune diseases (ADs) may predispose patients to higher radiation-induced toxicity, and no data are available regarding particle therapy. Our objective was to determine if cancer patients with ADs have a higher incidence of complications after protons (PT) or carbon ion (CIRT) therapy. METHODS. In our retrospective monocentric study, 38 patients with ADs over 1829 patients were treated with particle therapy between 2011 and 2020. Thirteen patients had collagen vascular disease (CVD), five an inflammatory bowel disease (IBD) and twenty patients an organ-specific AD. Each patient was matched with two control patients without ADs on the basis of type/site of cancer, type of particle treatment, age, sex, hypertension and/or diabetes and previous surgery. RESULTS. No G4–5 complications were reported. In the AD group, the frequency of acute grade 3 (G3) toxicity was higher than in the control group (15.8% vs. 2.6%, p = 0.016). Compared to their matched controls, CVD–IBD patients had a higher frequency of G3 acute complications (27.7 vs. 2.6%, p = 0.002). There was no difference between AD patients (7.9%) and controls (2.6%) experiencing late G3 toxicity (p = 0.33). The 2 years disease-free survival was lower in AD patients than in controls (74% vs. 91%, p = 0.01), although the differences in terms of survival were not significant. CONCLUSIONS. G3 acute toxicity was more frequently reported in AD patients after PT or CIRT. Since no severe G4–G5 events were reported and in consideration of the benefit of particle therapy for selected cancers, we conclude that particle therapy should be not discouraged for patients with ADs. Further prospective studies are warranted to gain insight into toxicity in cancer patients with ADs enrolled for particle therapy.