Impact of intensity-modulated radiation therapy on corneal endothelial cell for head and neck tumors not involving the orbital area

Objective  To explore the impact of intensity-modulated radiotherapy (IMRT) on corneal endothelial cells in patients with head and neck tumors that do not involve the orbital area.

Methods  A prospective cohort study was conducted. Thirty-one patients (60 eyes) with head and neck tumors not involving the orbital area who received head and neck IMRT at the Fourth Hospital of Hebei Medical University from August 2023 to January 2024 were selected as the radiotherapy group. The coefficient of variation (CV) of corneal endothelial cells, hexagonality (HEX), corneal endothelial cell density (ECD), and central corneal thickness (CCT) were measured and recorded before radiotherapy and 1 day, 3 months, and 6 months after radiotherapy. Meanwhile, 30 normal subjects (60 eyes) were selected as the normal control group for measuring CV, HEX, ECD, and CCT. The differences in the above indicators between the normal control group and the radiotherapy group before radiotherapy were compared, as well as the changes in the above indicators in the radiotherapy group before and after radiotherapy. The study adhered to the Declaration of Helsinki. The study protocol was approved by The Fourth Hospital of Hebei Medical University (No. 2023ks120). All subjects were aware of the study purpose and signed written informed consent.

Results  No significant differences were observed in age or corneal parameters between the radiotherapy group prior to treatment and the normal control group ( t=0.294, 0.704, 0.752, 0.023, 0.059; all P>0.05). There were significant differences in the overall comparison of CV and HEX, at different time points before and after radiotherapy in the radiotherapy group ( Z=12.087, P=0.007; F=6.632, P<0.001). CV at 6 months post-radiotherapy decreased compared to at 1 day post-treatment, showing a statistically significant difference ( P<0.05). HEX at 3 months post-treatment was decreased compared to pre-treatment and 1 day post-treatment, and the HEX at 6 months post-radiotherapy was decreased compared to 1 day post-treatment, showing statistically significant differences (all P<0.05). The ECD values before treatment, at 1 day, 3 months, and 6 months post-radiotherapy were 2 675(2 575, 2 844), 2 597(2 507, 2 740), 2 601(2 501, 2 768), and 2 609(2 544, 2 755)cells/mm ^2, respectively, with a statistically significant difference, and ECD at different time points after treatment were lower than pre-treatment ( Z=42.727, P<0.001), showing statistically significant differences (all P<0.001). There was no statistically significant difference in the overall comparison of CCT at different time points before and after radiotherapy ( Z=6.458, P=0.091). At 1 day, 3 months, and 6 months after radiotherapy, none of the subjects in the radiotherapy group exhibited visual acuity decline, positive corneal fluorescein staining, or abnormal findings under slit-lamp microscopy.

Conclusions  Patients with head and neck tumor not involving the orbital area receiving head and neck IMRT experience short-term morphological changes in corneal endothelial cells, which gradually return to normal, and the corneal ECD decrease without causing change in corneal thickness.