Dosimetric Evaluation of Hippocampus Sparing Intensity Modulated Radiation Therapy in Patients With Stage T1-T2 and Stage T3-T4 Nasopharyngeal Carcinoma

Xiaofeng Zhou; Kui Wu; Niharika Prasad; Sanjay Jaiswal; Biao Jiang; Xia Li; Wenzheng Sun; Lingli Mao; Kanghua Huang; Minghan Shi; Shen Li; Qichun Wei

doi:10.1016/j.adro.2024.101646

Dosimetric Evaluation of Hippocampus Sparing Intensity Modulated Radiation Therapy in Patients With Stage T1-T2 and Stage T3-T4 Nasopharyngeal Carcinoma

Adv Radiat Oncol. 2024 Sep 27;9(11):101646. doi: 10.1016/j.adro.2024.101646. eCollection 2024 Nov.

Authors

Xiaofeng Zhou¹, Kui Wu², Niharika Prasad³, Sanjay Jaiswal⁴, Biao Jiang⁵, Xia Li², Wenzheng Sun², Lingli Mao², Kanghua Huang¹, Minghan Shi⁶, Shen Li¹, Qichun Wei¹

Affiliations

¹ Department of Radiation Oncology, The Second Affiliated Hospital, National Ministry of Education Key Laboratory of Cancer Prevention and Intervention, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People's Republic of China.
² Department of Radiation Oncology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People's Republic of China.
³ Department of Conservative Dentistry and Endodontics, Saraswati Dental College, Lucknow, Uttar Pradesh, India.
⁴ Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People's Republic of China.
⁵ Department of Radiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People's Republic of China.
⁶ Department of Internal Medicine, Thunder Bay Regional Health Sciences Foundation, Thunder Bay, Ontario, Canada.

Abstract

Purpose: To compare the hippocampus (HPC) dose reduced by HPC-sparing intensity modulated radiation therapy (IMRT) plans between nasopharyngeal carcinoma (NPC) patients of stages T1-T2 and T3-T4, and to investigate the correlation between the dose of the HPC and the volume of PTV_nx70 (the planning target volume of the primary tumor in the nasopharynx that received 70 Gy).

Methods and materials: Fifty-eight NPC patients were retrospectively evaluated. HPC-nonsparing IMRT or sparing IMRT for each patient was designed according to the protocol for NPC. Dose-volume histogram was used to evaluate the IMRT plans for each patient. The difference in values of HPC parameters (eg, D_min[NS] - D_min[S]) between HPC-sparing and nonsparing plans in the stage T1-T2 group and stage T3-T4 group were compared. The correlations between the dose of the HPC and the volume of PTV_nx70 were analyzed.

Results: There was no significance between HPC-sparing and nonsparing IMRT plans. Compared with the HPC-nonsparing plans, the HPC-sparing plans significantly decreased both dosimetric and volumetric parameters for the HPC (P < .05), except for D_min, D_98%, and V₅. The medians of D_median[NS] - D_median[S], D_mean[NS] - D_mean[S], D_40%[NS] - D_40%[S], V₃₀[NS] - V₃₀[S], V₄₀[NS] - V₄₀[S] and V₅₀[NS] - V₅₀[S] in the T1-T2 group were significantly lower than in the T3-T4 group (P < .05), respectively. Both dosimetric and volumetric parameters for the HPC were positively correlated with the volume of PTV_nx70 in HPC-sparing and HPC-nonsparing plans (P < .05). The volume of PTV_nx70 was positively correlated with D_median[NS] - D_median[S], D_mean[NS] - D_mean[S], D_40%[NS] - D_40%[S], V₄₀[NS] - V₄₀[S] and V₅₀[NS] - V₅₀[S] (P < .05).

Conclusions: HPC-sparing IMRT plans may play a more significant role in decreasing D_median, D_mean, D_40%, and V₃₀-V₅₀ of HPC in NPC patients with stages T3-T4 than those in stages T1-T2. PTV_nx70 volume of NPC patients is positively correlated with all dosimetric and volumetric parameters of HPC and the reduction of specific dosage parameters by HPC-sparing IMRT plans.