应用MRI探讨鼻咽癌的分布及其颅底侵犯的规律

目的 探讨鼻咽癌原发肿瘤的分布特点及其侵犯颅底骨质的规律.方法 收集2002年11月至2005年1月中山大学肿瘤医院连续确诊的初诊鼻咽癌住院患者838例,在治疗前2周以内行磁共振成像(MRI)检查,由两位经验丰富的影像学医师双盲法阅片,统计原发灶和颅底骨质受侵的部位及数目,并分析其间的关系.结果 有争议时由课题组讨论决定.结果 838例鼻咽癌患者中,侵犯顶壁和顶后壁者分别占据总病例数的98.6%(826/838)和9 8.2%(823/838),两者差异无统计学意义(P＞0.05).侧壁受累者784例(93.6%),鼻咽后壁受累者391例(46.7%).颅底骨质受侵的总体发生率为65.5%(549/838),根掘肿瘤侵犯的解剖部位划分,可分为向前侵犯,向外侧侵犯,向外上侵犯,向前上侵犯和后上侵犯5种模式.按发生率划分为3组:高危组(≥35%),中危组(≥5%～35%)和低危组(＜5%).通过将鼻咽癌颅底受侵与鼻咽癌分期对比,结果高危组和中危组对应于T3期,低危组对应于T4期.结论 鼻咽癌颅底侵犯主要为由近及远逐级的方式,其中以向上和向外上侵犯者发生率最高.鼻咽癌颅底侵犯区域分为高危组、中危组和低危组.建议将高危组划为T3a期,中危组划为T3b期,低危组划为T4期.

Distributions of primary nasopharyngeal carcinoma tumor and patterns of skull base erosion detected by magnetic resonance imaging

Objective To evaluate the distributions of primary nasopharyngeal carcinoma (NPC) and the patterns of skull base involvement in NPC patients using magnetic resonance imaging (MRI).Methods After the approval of institutional review board and informed consent, 838 consecutive newlydiagnosed and untreated NPC patients were examined by MRI. Their MR images were reviewed by two independent radiologists. Results Among all cases, the incidence rates of superior side and post-superior side involvement were 98. 57% (826/838) and 98. 21% (823/838) respectively. The differences were not significant between these two sides (P ＞ 0. 05). Lateral side erosion was demonstrated in 784 (93. 56%)cases. Posterior side was involved in 391 (46. 66%) cases. The total incidence rate of skull base involvement was 65.51% (549/838). According to the anatomic site, the pathways of skull base involvement were classified into 5 spreading routes: anterior; superior; super-lateral; super-anterior and super-posterior. According to the incidence rates and the results of chi-square test, the anatomic sites around the nasopharynx were classified into three groups of risk grades: high-risk (≥35%), medium-risk (≥5%-35%) and low-risk (＜ 5%). Conclusion Skull base involvement of NPC spreads stepwise from proximal site to more distal sites. The area of skull base involvement in NPC is classified into high-grade,medium-grade and lower-grade groups respectively. The high and medium-grade groups are related with T3 stage while the lower-grade group T4 stage. Thus T3 stage should be subdivided into T3a and T3b. These schemes may be useful in a more accurate NPC staging and a delineation of clinical target volume for radiotherapy in NPC patients.