初治鼻咽癌调强放疗的初步结果

Preliminary results of intensity modulated radiation therapy for untreated nasopharyngeal carcinoma

目的分析调强放疗(IMRT)在初治鼻咽癌应用的初步结果。方法76例经病理证实的初治鼻咽癌患者接受了全程IMRT。根据1992年福州分期标准,Ⅰ期2例,Ⅱ期20例,Ⅲ期29例,Ⅳ期25例。采用多叶光栅的静态调强技术实施IMRT,采用的逆向治疗计划系统分别为TMS、CMS和Pinnacle。各靶区处方剂量均以其PTV定义给予,鼻咽肿瘤(GTV)和颈部淋巴结(GTV-LN)处方剂量为68～76 Gy,鼻咽区域及上颈部临床靶区(CTV1)处方剂量为58～66 Gy。下颈部锁骨上区域(CTV2)37例采用IMRT技术,处方剂量为50～60 Gy,39例采用常规技术单前切线野照射。晶体、脑干、脊髓、视神经和视交叉的最高限量(99%体积低于此剂量)分别为8、54、40、54、54 Gy。7例合并同时化疗,4例IMRT后鼻咽局部予以立体定向放疗加量。采用Kaplan-Meier法计算生存率,RTOG标准评价急性副反应。结果中位随访期为10个月,全组死亡3例,分别死于鼻咽肿瘤未控大出血、肝转移和治疗相关并发症。1、2年总生存率分别为92%、92%；鼻咽和颈部1、2年局部控制率均为95%,4例出现了远处转移；1、2年无瘤生存率分别为95%、86%。急性反应以1、2级为主,其中唾液腺为99%,咽部和黏膜分别为88%和72%。GTV、GTV-LN、CTV1、CTV2的平均剂量均值分别为74．3、74．1、67．2、60．2 Gy,平均低于95%处方剂量的靶区体积分别为0．58%、0．31%、0．67%、0．59%。左、右腮腺的中位剂量分别为33．9、34．0 Gy,晶体、脑干、脊髓、视神经、交叉最高剂量平均值分别为7．2、53．4、41．6、53．4、55．6 Gy。结论调强放疗技术能对初治鼻咽癌的各靶区达到很好的剂量分布,达到较高局部控制率,并降低了周围危及器官剂量和急性治疗反应,远期结果需进一步观察。

Objective To report the preliminary results of our experience with intensity modulated radiation therapy（IMRT） in the treatment of untreated nasopharyngeal carcinoma. Methods From November 2001 to April 2005, 76 patients with nasopharyngeal carcinoma received IMRT as the first-line treatment. According to the 1992 Fuzhou staging system, 2 patients had Stage 1, 20 Stage Ⅱ , 29 Stage ⅢI, and 25 Stage Ⅳ lesion. IMRT treatment planning was accomplished by one of three inverse treatment planning systems： TMS, CMS or Pinnacle with the radiation delivered by the technique of computer controlled autosequencing static multileaf collimator（MLC）. The lower neck and supraclavicular area was irradiated with the conventional technique using an anterior field in 39 patients, or the way of IMRT in 37 patients. The prescribed dose was 68-76 Gy to the gross tumor volume （G3N） and positive neck nodes （GTV-LN）, 60 Gy to the clinical target volume （CTV1）, encompassing the upper neck and area around the nasopharynx, 50-60 Gy to the lower neck and supraclavicular area（CTV2）. Four（6% ） patients had fractionated steretactic fractianated radiotherapy as boost. Seven（9%） patients, mostly patients with advanced lesion, also received cisplatin or paclitaxol during radiotherapy. Acute normal tissue effects were graded according to the Radiation Therapy Oncology Group（RTOG） radiation morbidity scoring criteria. Loco-regional progressian-free, distant metastasis-free survival and overall survival were estimated using the Kaplan-Meier method. Results The median follow-up interval was 10 months （range, 1-45 months）. The 2-year overall survival was 92%, and the 2-year loco-regional progression-free survival was 95%. Four patients have developed distant metastasis, their 1-year and 2-year disease-free survival was 95% and 86%. Three patients have died during the follow-up, one of progression of primary tumor, one other of distant metastasis and the third from pneumo-nia. Aeute toxicity was mostly Grade 1 to Grade 2： salivary gland 99%, pharynx 88%, and mueositis 72%. Analysis of the dose-volume histograms （DVHs） showed that the average mean dose delivered to the GTV, GTV-LN, CTV1 and CTV2 was 74.3, 74.1, 67.2 and 60.2 Gy, respeetively. The average volume whieh received less than 95% of the prescribed dose for these targets was 0.58%, 0.31%, 0.67% and 0.59%, respectively. The average dose to 50% of the fight and left parotid glands was 33.9 Gy and 34.0 Gy. The average value of maximum dose of the lens, brainstem, spinal eord, optie nerve and optie ehiasma was 7.2,53.4,41.6, 53.4 and 55.6 Gy, respeetively. Conclusions Intensity modulated radiation therapy improves the target volume eoverage with signifieant sparing of the salivary glands and the other nearby eritieal normal struetures. Intensity modulated radiation therapy results in good loeo-regional eontrol rate and lower aeute toxieity. Prolonged follow-up is needed to prove its long-term result.