Pathological classification of chronic radiation-induced intestinal injury and its clinical implications.

Background: Chronic radiation-induced intestinal injury (CRIII) is the most prevalent condition following radiation therapy in patients with pelvic malignancies. More than 15% of patients with severe CRIII require surgery. The histopathological features and their interactions with clinical presentation and outcomes remain largely unknown. The present study proposed a new pathological categorization of CRIII and investigated its relationship with clinical manifestations and outcomes.

Methods: This retrospective study included 111 patients with CRIII who were treated at the Sixth Affiliated Hospital of Sun Yat-sen University (Guangzhou, China) between January 2011 and December 2021. The features of ulcers, collagen fibers, and neoangiogenesis were measured via microscopic scoring, Masson's trichrome staining, and immunohistochemistry for CD34. The K-means method was used for cluster analysis based on these three data groups. The Kaplan-Meier method and log-rank test were used to examine the incidence-time curves of severe complications, including intestinal fistula, intestinal obstruction, and anemia, as endpoint events. Cox proportional hazards regression models were used for multivariate analyses.

Results: Four pathological CRIII subtypes were identified: mixed (48.7%), fibrosis (17.1%), telangiectasia (16.2%), and ulcers (18.0%). Patients with the ulcer subtype had a significant probability of developing a recto-intestinal fistula (P = 0.047) and a pathological pattern of deep serosal ulcers, which manifested as fistulas and thrombosis (75%, 15/20). Patients with the telangiectasia subtype consistently exhibited anemia (P = 0.002) and displayed significant arterial dilatation (72.2%, 13/18). Intestinal obstruction occurred more frequently in the fibrosis subtype due to a severe fibrotic pattern (31.6%, 6/19) and sclerotic collagen (57.9%, 11/19) (P = 0.014).

Conclusion: We proposed a new pathological classification for CRIII that better associates with clinical presentations and consequences.