Advancements in nasopharyngeal carcinoma radiotherapy: Dosimetric evaluation of arc therapy with hippocampal sparing.

BACKGROUND

Nasopharyngeal carcinoma (NPC) is located near critical structures like the hippocampus, essential for memory and cognitive function. While Volumetric Modulated Arc Therapy (VMAT) has improved dose conformity in NPC treatment, the integration of hippocampal-sparing (HS) approaches remains underexplored. This study evaluates the dosimetric feasibility and effectiveness of hippocampal-sparing VMAT (HS-VMAT) in NPC, focusing on reducing radiation exposure to the hippocampus while maintaining target volume coverage.

METHODS

We conducted a retrospective cohort study of 20 NPC patients treated at Cheikh Khalifa International University Hospital between 2020 and 2023. Each patient underwent two radiotherapy plans: one with hippocampal sparing and one without. Dosimetric parameters for planning target volumes (PTVs) and organs at risk (OARs) were analyzed. Independent samples t-tests were used for statistical analysis with a significance level of p < 0.05.

RESULTS

For the high-risk PTV (PTV HR), there were no significant differences in maximum dose (D2 %) between HS and non-HS groups (71.71 ± 0.23 Gy vs. 71.65 ± 0.11 Gy; p = 0.298). The minimum doses (D95 %, D98 %) and mean dose (Dmean) were slightly lower in the HS group, though not statistically significant. For intermediate- and low-risk PTVs, dose metrics remained similar across groups. Hippocampal sparing significantly reduced doses to the hippocampus. The minimum dose (Dmin) decreased from 5.87 ± 2.06 Gy to 3.93 ± 0.45 Gy (p = 0.001), and the maximum dose (Dmax) decreased from 10.73 ± 3.62 Gy to 7.40 ± 1.25 Gy (p = 0.001). Radiation doses to critical structures were also reduced. The brainstem Dmax decreased from 35.68 ± 5.31 Gy to 30.12 ± 4.71 Gy (p = 0.001), and the left parotid gland Dmoy decreased from 21.38 ± 5.38 Gy to 18.32 ± 2.53 Gy (p = 0.029).

CONCLUSION

HS-VMAT for NPC effectively reduces hippocampal and critical structure radiation doses without compromising target volume coverage. This technique offers a feasible approach to minimize neurocognitive risks while maintaining treatment efficacy.