Loosening Neuro-Optic Structures Dosimetric Constraints Provides High 5-Year Local Recurrence-Free Survival With Acceptable Toxicity in T4 Nasopharyngeal Carcinoma Patients Treated With Intensity-Modulated Radiotherapy

Tingting Zhang; Meng Xu; Jinglin Mi; Hui Yang; Zhengchun Liu; Lulu Huang; Kai Hu; Rensheng Wang

doi:10.3389/fonc.2021.598320

Loosening Neuro-Optic Structures Dosimetric Constraints Provides High 5-Year Local Recurrence-Free Survival With Acceptable Toxicity in T4 Nasopharyngeal Carcinoma Patients Treated With Intensity-Modulated Radiotherapy

Front Oncol. 2021 Feb 22:11:598320. doi: 10.3389/fonc.2021.598320. eCollection 2021.

Authors

Tingting Zhang¹, Meng Xu¹, Jinglin Mi¹, Hui Yang², Zhengchun Liu³, Lulu Huang¹, Kai Hu¹, Rensheng Wang¹

Affiliations

¹ Department of Radiation Oncology, The First Affiliated Hospital of Guangxi Medical University, Nanning, China.
² Department of Oncology, Liuzhou Worker Hospital, Liuzhou, China.
³ Department of Radiotherapy, Affiliated Hospital of Guilin Medical University, Guilin, China.

Abstract

Objective: Whether the original dosimetric constraints of neuro-optic structures (NOS) are appropriate for patients with nasopharyngeal carcinoma (NPC) undergoing intensity-modulated radiotherapy (IMRT) remains controversial. The present study compared the survival rates and radiation-induced optic neuropathy (RION) occurrence between T4 NPC patients whose NOS were irradiated with a near maximum dose received by 2% of the volume (D2%) >55 Gy and ≤55 Gy. Moreover, the NOS dosimetric parameters and their correlation with RION occurrence were also evaluated.

Methods: In this retrospective study, 256 T4 NPC patients treated with IMRT between May 2009 and December 2013 were included. Patient characteristics, survival rates, dosimetric parameters, and RION incidence were compared between the D2% ≤55 Gy and D2% >55 Gy groups.

Results: The median follow-up durations were 87 and 83 months for patients in the D2% >55 Gy and D2% ≤55 Gy groups, respectively. The 5-year local recurrence-free survival rates were 92.0 and 84.0% in the D2% >55 Gy and D2% ≤55 Gy groups (P = 0.043), respectively. There was no significant difference in the 5-year overall survival (OS) between both groups (D2% >55 Gy, 81.6%; D2% ≤55 Gy, 79.4%; P = 0.586). No patients developed severe RION (Grades 3-5), and there was no significant difference (P = 0.958) in the incidence of RION between the two groups. The maximum dose of NOS significantly affected the RION incidence, with a cutoff point of 70.77 Gy.

Conclusion: Appropriately loosening NOS dosimetric constraints in order to ensure a more sufficient dose to the target volume can provide a better 5-year local recurrence-free survival and acceptable neuro-optic toxicity in T4 NPC patients undergoing IMRT.

Keywords: dosimetric constraints; intensity-modulated radiotherapy; nasopharyngeal carcinoma; neuro-optic structures; radiation-induced optic neuropathy.