北京大学人民医院胸外科、肺癌及胸部微创中心

客观认识PET在非小细胞肺癌术前评估中的地位

北京大学人民医院胸外科、胸部微创中心 100044

王俊

手术安全性评估是术前准备的主要内容，也是关乎手术成败的关键环节。它主要包括全身主要器官机能状态评估和肿瘤的可切除性评估两大部分。通常大家都觉得后者更客观和便于把握。然而，约30%-60%早期（I、II期）非小细胞肺癌在术后短期（<5年）内死于复发和转移的事实【1】，使我们清醒地认识到，目前用于肺癌分期的常规评估手段还远不能满足临床工作的需要。1990年代中期以后，随着PET在临床应用的推广，一些人把肺癌准确分期的希望都寄托在PET上。早期的临床报告似乎也在迎合这种企望，PET对肿瘤和纵隔淋巴结诊断的敏感性、特异性和准确性都在93%以上【2】，使得部分医生坚信找到了理想的分期手段，有人甚至认为PET可以取代CT和纵隔镜等常规分期方法。近年来，越来越多的资料显示，PET的假阳性和假阴性率都在升高，尤其是前者【3，4】。近期的结果提示，PET在肺癌纵隔淋巴转移的评估中，敏感性仅为64.4 %【3】。看来，正如当年CT无法取代纵隔镜一样，PET也不能取代CT和纵隔镜等传统评估技术。但是，它能否和CT一样，成为肺癌术前分期的一种有效的、不可或缺的补充手段呢？由于目前大多数报告尚属回顾性或较片面，并且有时还存在相互矛盾的结果。如何客观地评价PET在非小细胞肺癌术前评估中的地位一直是胸外科界关注的热点之一【5】。

这篇由Tineren等内科医生所做的多中心随机对照研究，是迄今关于PET用于非小细胞肺癌术前评估方面比较有影响的文章【6】。它将PET与非小细胞肺癌术前评估紧密结合进行探讨，再次证明了PET在非小细胞肺癌分期中的价值，尤其是在发现远处转移方面的突出作用。但是，仔细读后觉得，这篇文章除了给出“无益开胸”这个内科医师和病人特别关注的新指标外，在肺癌的T、N、M分期方面并无新意。另外，作者所界定的“无益开胸”标准也值得商榷；比如，大部分良性肺肿物也是开胸手术的适应证，不能一概视为无价值的开胸。总之，这项研究设计比较合理，资料很全面，论述清晰，具有很强的说服力，还是一篇很不错的临床研究报告；对胸外科医生正确认识和应用PET技术具有一定的指导意义。

事实上，经过10余年的临床实践，目前对PET认识更加客观和理性了。PET在非小细胞肺癌术前评估中的地位也趋明晰。首先，在原发瘤的评估方面，其作用目前仅限于对单发肺内结节的良恶性鉴别，并且阳性预测值相对较低【7】，在肿瘤可切除性评估方面的作用远逊于CT；更何况肺内良性肿瘤也需要手术切除，而那些不需要手术的病灶，比如活动性结核瘤及炎性肿物，PET 的假阳性率又太高。在纵隔淋巴结评估方面，其敏感性和准确性虽都较CT高，但假阳性率也越来越接近CT【3】，尤其是在结核发病率较高的国家和地区；目前的观点是，纵隔淋巴结PET阳性者一定要行纵隔镜分期，PET阴性者是否做纵隔镜检查还有争议【5】。对于远处转移的评估，是迄今在术前评估中最能体现PET价值和优势的地方；从这篇文章的结果中也可以看出，除了有争议的肺良性病变外，影响两组“无益开胸”率的关键因素就是术前CWU+PET组较CWU组发现了更多有远处转移的病人（7/92vs 1/96）；在Kalff 等报告的105例非小细胞肺癌病人中，经PET检查新发现存在远处转移者达26%，其中67%的病人因此而改变了治疗方法【8】; Vergagen等人的结果也与之类似【4】。相信，随着检查技术的不断提高、经验的进一步积累以及检查费用的逐步降低，PET在非小细胞肺癌术前评估中的应用将会更加普及，成为术前评估的重要补充方法，并将显著提高术前评估的水平。

参考文献

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van Tinteren H, Hoekstra OS, Smit EF, van den Bergh JH, Schreurs AJ, Stallaert RA, van Velthoven PC, Comans EF, Diepenhorst FW, Verboom P, van Mourik JC, Postmus PE, Boers M, Teule GJ.

Effectiveness of positron emission tomography in the preoperative assessment of patients with suspected non-small-cell lung cancer: the PLUS multicentre randomised trial. Lancet. 2002 Apr 20;359(9315):1388-93.

Comprehensive Cancer Centre Amsterdam, Amsterdam, Netherlands. h.v.tinteren@nki.nl

BACKGROUND: Up to 50% of curative surgery for suspected non-small-cell lung cancer is unsuccessful. Accuracy of positron emission tomography (PET) with 18-fluorodeoxyglucose (18FDG) is thought to be better than conventional staging for diagnosis of this malignancy. Up to now however, there has been no evidence that PET leads to improved management of patients in routine clinical practice. We did a randomised controlled trial in patients with suspected non-small-cell lung cancer, who were scheduled for surgery after conventional workup, to test whether PET with 18FDG reduces number of futile thoracotomies. METHODS: Before surgery (mediastinoscopy or thoracotomy), 188 patients from nine hospitals were randomly assigned to either conventional workup (CWU) or conventional workup and PET (CWU+PET). Patients were followed up for 1 year. Thoracotomy was regarded as futile if the patient had benign disease, explorative thoracotomy, pathological stage IIIA-N2/IIIB, or postoperative relapse or death within 12 months of randomisation. The primary outcome measure was futile thoracotomy. Analysis was by intention to treat. FINDINGS: 96 patients were randomly assigned CWU and 92 CWU+PET. Two patients in the CWU+PET group did not undergo PET. 18 patients in the CWU group and 32 in the CWU+PET group did not have thoracotomy. In the CWU group, 39 (41%) patients had a futile thoracotomy, compared with 19 (21%) in the CWU+PET group (relative reduction 51%, 95% CI 32-80%; p=0.003). INTERPRETATION: Addition of PET to conventional workup prevented unnecessary surgery in one out of five patients with suspected non-small-cell lung cancer.