Background and objectives Radiotherapy for advanced cervical cancer (CaCx) often results in unintended genitourinary toxicities, notably bladder damage. Predicting such radiation-induced toxicity remains challenging. γ-H2AX, a marker of DNA double-strand breaks (DSBs), offers promise as a predictive biomarker for radiosensitivity. This study aimed to evaluate γ-H2AX foci kinetics in peripheral blood lymphocytes (PBLs) as a surrogate for DNA damage response and a predictor of bladder toxicity in CaCx patients undergoing pelvic radiotherapy. Methods In this prospective study, 43 FIGO stage IIIB CaCx patients were enrolled. Stage I (n=31) assessed γ-H2AX induction post-CT simulation (2–6 mGy); Stage II (n=34) evaluated γ-H2AX kinetics across three radiotherapy fractions (FR1, FR13, FR25) during external beam radiotherapy (50 Gy in 25 fractions ± cisplatin). Blood samples were collected at baseline, 1-, 4-, and 24-h post-irradiation. γ-H2AX foci were quantified via flow cytometry. Bladder toxicity was graded usingRadiation Therapy Oncology Group (RTOG) criteria. Results CT and radiotherapy both induced significant γ-H2AX foci, peaking at 1 h. Patients without bladder toxicity showed higher foci induction and faster decay (1→4h: 48.9% vs . 39.4%; 1→24h: 43.6% vs . 12.8%) across all fractions. Persistent foci at 24 h correlated with increased toxicity risk, indicating deficient DNA repair capacity. Interpretation and conclusions γ-H2AX foci kinetics effectively reflect in vivo DNA repair efficiency and predict radiation-induced bladder toxicity. This minimally invasive biomarker may guide personalized radiotherapy, enabling early identification of high-risk patients and potential use of radioprotectors or treatment modifications.
John et al. (Sat,) studied this question.