Frailty profiles and symptomatic radiation pneumonitis in patients with lung cancer undergoing radiotherapy: A latent class analysis.

Objective: This study aimed to identify distinct frailty subtypes and their influencing factors, and to further explore the relationship between these frailty characteristics and the occurrence of symptomatic radiation pneumonitis (SRP) in patients with lung cancer undergoing radiotherapy. Methods: The Observational study was conducted among 204 patients with lung cancer undergoing radical radiotherapy. Frailty was assessed via the Fried Frailty Phenotype, and nutritional risk was evaluated by the Nutrition Risk Screening 2002 (NRS-2002). Radiation pneumonitis (RP) was graded by the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 in conjunction with chest CT results. Radiotherapy parameters, including total radiation dose, treatment technique, bilateral lung mean dose (Dmean, Gy), and bilateral lung V20 (%), were collected. Latent class analysis (LCA) was performed to identify potential frailty subgroups. Multinomial logistic regression was conducted to determine factors associated with frailty classes, and binary logistic regression was subsequently used to assess the relationship between frailty class and the incidence of SRP in patients with lung cancer. Results: LCA identified three distinct frailty subgroups: prefrailty (C1, 37.3%), frail physical activity decline (C2, 31.9%), and severe-frail core-strength decline (C3, 30.9%) group. Radiotherapy sessions, nutritional risk, and age were the main factors influencing frailty classification. The incidence of SRP in group C3 (68.3%) was significantly higher than that in group C2 (47.7%) and group C1 (19.7%) ( Conclusions: Frailty among patients with lung cancer undergoing radiotherapy exhibit marked frailty heterogeneity. Those with severe frailty, particularly characterized by core strength and physical function decline, strongly associated with increased SRP risk. These findings indicating the importance of individualized nursing assessments and early, targeted interventions to prevent and mitigate frailty progression and SRP occurrence. Trial registration: National Clinical Trial Registry (ChiCTR2400081213).