The Diagnostic Trap in Radiation-Induced Mesothelioma: Kinetic-Morphological Decoupling Masks Molecular Aggression.

Background: In malignant pleural mesothelioma, epithelioid histology is traditionally considered a favorable prognostic marker. However, it remains clinically undetermined whether the intensity of an oncogenic insult can disrupt this link. Radiation-induced cases serve as an unconfounded biological model to dissect such trajectories masked by asbestos confounding. Methods: We performed an Individual Patient Data (IPD) synthesis of 20 strictly asbestos-unexposed human cases, applying clinically established dose stratification (intermediate: 20-45 Gy vs. high: >45 Gy). To confirm the observed pattern, we examined data from 829 dogs in the Colorado State University (CSU) Beagle Study. Results: In the intermediate-dose group (n = 13), a significant positive correlation persisted between age at radiotherapy and the latent period (ρ = 0.567, p = 0.043). Conversely, high-dose exposure (>45 Gy) showed a disruption of this age-dependent pattern, with a trend toward inverse correlation (ρ = -0.754, p = 0.084). Interaction analysis confirmed a statistically significant divergence between these dose-dependent trends (p = 0.005). The CSU Beagle Study (n = 829) demonstrated the physical basis of this phenomenon: in the canine model, high-dose exposure (≥0.74 Gy) triggered a "Step-Jump" in cumulative incidence (30.4% at 0.5 years), indicating instantaneous carcinogenic onset distinct from cumulative biological aging. Conclusions: This kinetic divergence points to a "Diagnostic Trap." We propose a 'Single- to Double-Brake' framework where intermediate doses preserve age-dependent progression, whereas high doses likely trigger catastrophic genomic failure (chromothripsis) that bypasses the time required for morphological dedifferentiation. Consequently, morphologically indolent epithelioid tumors in high-dose survivors may harbor aggressive molecular profiles not predicted by histology alone, necessitating risk-stratified precision surveillance.