鼻咽癌N0‐N1期患者Ⅱb区临床靶区剂量优化策略及可行性分析

目的 明确鼻咽癌N₀‐N₁期患者Ⅱ_b区淋巴结预防照射剂量CTV_60Gy优化至CTV_50Gy的安全性以及对腮腺保护的剂量优势和临床价值,了解PET‐CT及弥散加权成像（DWI）对颈部可疑阳性淋巴结（最大横断面短径≥5 mm但<10 mm）的诊断价值。方法 回顾性分析2015年6月至2017年3月收治的N₀‐N₁期初治非转移鼻咽癌157例,其中104例在多模态影像指导下进行上颈部Ⅱ_b区临床靶区优化,以Kaplan‐Meier法进行生存分析,单因素、多因素回归分析颈部淋巴结复发模式,配对t检验比较剂量优化前后靶区及腮腺剂量参数差异。结果 N₁期行对侧单颈Ⅱ_b区优化60例,行双颈Ⅱ_b区优化25例（仅咽后淋巴结转移者）;N₀期双颈Ⅱ_b区优化19例。共有3例患者出现颈部复发,均在高剂量区内。全组5年总生存率为93.3%,淋巴结无复发生存率、无局部复发生存率、无远处转移生存率和无瘤生存率分别为97.1%、91.3%、88.5%和80.8%。颈淋巴结复发与鼻咽局部复发有关,与咽后淋巴结状态无关。14例患者Ⅱ_b区内有可疑阳性颈淋巴结,最大横截面短径平均为7.1（5~9） mm,其中11例PET‐CT阳性,平均SUV_max为2.96（2.5~3.3）。优化后肿瘤体积的差异无统计学意义（P>0.05）,腮腺的D_mean、D_max、D_50%、V_26Gy显著低于常规计划（P<0.01）。结论 鼻咽癌N₀‐N₁患者进行Ⅱ_b区CTV_60Gy至CTV_50Gy的剂量优化是安全的,腮腺及颈部周围正常组织受照剂量明显降低,对于未达诊断标准的小淋巴结需要结合PET‐CT及DWI等多模态成像进行个体化处理。

The strategy and feasibility of dose optimization in clinical target volume Ⅱb in patients with N0‐N1 nasopharyngeal carcinoma

Objective To determine the safety of prophylactic irradiation dose CTV_60Gy optimized to CTV_50Gy for II_b region in patients with stage N₀‐N₁ nasopharyngeal carcinoma (NPC) and the dose advantage and clinical value for parotid gland protection, and to understand the diagnostic value of PET‐CT and diffusion‐weighted imaging (DWI) for suspicious positive lymph nodes in the neck (5 mm≤maximum short diameter<10 mm). Methods Clinical data of 157 patients with primary non‐metastatic NPC (N₀‐N₁) admitted to our hospital from June 2015 to March 2017 were retrospectively analyzed. 104 patients underwent II_b clinical target volume optimization guided by multimodal imaging system. Survival analysis was performed by Kaplan ‐ Meier method. Univariate/multivariate regression analysis was performed to analyze the pattern of cervical lymph node recurrence. Paired t‐test was used to compare the differences in target volume and parotid gland dose parameters before and after dose optimization. Results Sixty patients underwent single‐neck optimization in stage N₁, 25 patients received double‐neck optimization (only those with retropharyngeal lymph node metastasis), and 19 patients underwent double‐neck optimization in stage N₀. Three patients had cervical regional recurrence, all in‐field. The 5‐year overall survival rate was 93.3%. The lymph node recurrence‐free survival rate, local recurrence‐free survival rate, distant metastasis‐free survival rate and disease‐free survival rate were 97.1%, 91.3%, 88.5% and 80.8%, respectively. Cervical lymph node recurrence was associated with local recurrence in the nasopharynx, regardless of retropharyngeal lymph node status. Fourteen patients had suspicious positive cervical lymph nodes in II_b region, with a mean maximum short diameter of 7.1 (5~9) mm on the largest cross‐sectional plane, and 11 of them were positive on PET‐CT, with a mean SUV_max of 2.96 (2.5~3.3). There was no significant difference in GTV after optimization (P>0.05). D_mean, D_max, D_50% and V_26Gy of parotid gland were significantly lower than those of conventional plan (all P<0.01). Conclusions It is safe to optimize CTV_60Gy to CTV_50Gy in II_b region in patients with N₀‐N₁ NPC, and the exposure dose to normal tissues around the parotid gland and neck is significantly reduced. For small lymph nodes that do not meet the diagnostic criteria, it needs to be individualized in combination with multimodality imaging systems, such as PET‐CT and DWI.