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

Abstract

ObjectiveWhether 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.MethodsIn 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.ResultsThe 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.ConclusionAppropriately 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.

Radiation-Induced Retinopathy and Optic Neuropathy after Radiation Therapy for Brain, Head, and Neck Tumors: A Systematic Review

“…In total, 74 studies described a retrospective study design, and 4 studies described a prospective study design. Four studies distinguished two groups in the study population according to the tumor type or radiation therapy technique [ 19 , 20 , 21 , 22 ]. Therefore, we divided these studies and analyzed the subgroups as separate study groups.…”

“…In total, 29 studies reported the prevalence of retinopathy, including 2458 patients [ 1 , 7 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. Of these 29 studies, 27.6% were sinonasal tumors, 21% were nasopharyngeal tumors, 13.8% were maxillary sinus carcinoma, 10% were optic nerve sheath meningioma, 6.9% were head/neck cancers, and 3.4% consisted of skull base meningioma, cavernous malformation, and olfactory tumors.…”

“…Optic neuropathy was observed in 319 patients (prevalence = 2.0% [CI 95% = 0.028–0.034]). The diagnosis time of optic neuropathy was reported in 35 studies, with a mean of 36 months following irradiation (range, 3–108 months) [ 1 , 19 , 22 , 26 , 28 , 35 , 39 , 40 , 41 , 42 , 43 , 45 , 49 , 51 , 52 , 54 , 55 , 59 , 60 , 61 , 62 , 65 , 71 , 73 , 75 , 77 , 79 , 81 , 85 , 87 , 89 ]. Optic neuropathy prevalence was observed at prescribed doses of >50 Gy and <50 Gy at 4.5% and 1.7%, respectively.…”

“… Forest plot of the studies that reported radiation-induced optic neuropathy events [ 1 , 15 , 19 , 20 , 21 , 22 , 26 , 28 , 31 , 32 , 33 , 35 , 36 , 38 , 39 , 40 , 42 , 43 , 44 , 45 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , ...…”

“… Forest plot of subgroup studies that reported radiation-induced optic neuropathy events, <50 Gy ( p = 0) and >50 Gy ( p = 1) [ 1 , 19 , 22 , 26 , 28 , 35 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 49 , 51 , 52 , 54 , 55 , 59 , 60 , 61 , 62 , 65 , 71 , 73 , 75 , 77 , 79 , 81 , 85 , 87 , 89 ]. …”