结合式扫描可以正确分期大肠直肠癌


  December 5, 2006 — 根据一项发表于12月6日美国医学会期刊(JAMA)的研究报告,大肠直肠癌的分期可以透过一种结合两种影像检查的措施进行。
  
  该小型试验结果显示,同时进行结合正子摄影(PET)以及断层扫描(CT)的全身扫描,相较于分次进行这些检查是省时且「至少相等」的选择;这项研究也显示,单一结合式扫描比仅进行CT更准确,而CT是目前最常用来大肠直肠癌分期的工具。
  
  德国Essen大学医院资深作者Gerald Antoch医师向Medscape表示,结合PET/CT的大肠镜具有作为分期大肠直肠癌第一线诊断工具的潜力;然而,他也表示,这项试验结果是初期的,需要更多的样本数目来确认该试验结果。
  
  【比传统CT扫瞄更准确】
  Antoch医师与其同事针对47位过去由光学大肠镜与临床病征诊断为大肠直肠癌的病患进行试验;大肠镜在目前是侦测大肠直肠癌的标准工具,但是显然的,它只能提供肠胃道内的影像,下一步要检验的是,癌症是否已经扩散到淋巴结以及/或是固体器官,这通常是透过腹部与胸部CT进行。
  
  该试验显示,结合PET与CT扫描,相较于传统的方式,先进行大肠镜再进行CT,在侦测肿瘤、受侵犯淋巴结、与转移(TMN)的系统是更准确的(差异为22%;P=.003)。
  
  研究者表示,结合PET/CT扫描的结果改变了4位病患的治疗方式,改变是根据大肠直肠癌分级更准确的评估,以及进一步找出肿瘤,1位病患除了肝脏转移之外还患有肝细胞肿瘤,而另1位被发现罹患甲状腺肿瘤(在CT扫描中被误认为结节)。
  
  目前,在进行CT扫描后,如果结果并无定论,某些病患会接受PET扫描进一步的检查;作者指出当这样的步骤已经行之有年,但在临床筛检指引中并不建议常规性地这样做,即使是这项试验中使用的单一步骤结合PET/CT扫瞄。
  
  当研究者比较这两种措施(例如CT之后进行PET,相较于结合CT/PET扫描),他们发现在评估TNM分期上没有显著差异;然而,他们指出,单一步骤的方式比较不花时间,提供受转介医师单一一份报告,且对病患而言具「心理与生理上的」好处。
  
  Antoch医师向Medscape表示,结合PET/CT的大肠摄影可以一次针对整个大肠进行造影,免去传统多次检查对肿瘤进行分级的麻烦;他表示,传统的流程包括超音波、腹部以及/或是胸部CT扫描、胸部X光、以及PET扫描,且这些流程都需要相当一段时间。
  
  Antoch医师表示,结合PET/CT的机器已经在2001年上市,且目前世界上大约有2000部;这项研究中所使用的PET/CT大肠摄影需要一种以水为主要成分的灌肠剂,用来使大肠胀满,他希望日后该摄影流程可以被其它机构采用。
  
  Antoch医师表示,他的团队已经将研究中所使用的PET/CT大肠摄影流程与日常执业结合,他表示,一开始被诊断为大肠直肠癌的病患,仅需接受PET/CT大肠摄影作为肿瘤分级的工具。
  
  Antoch医师向Medscape表示,他将鼓励研究医师结合这样的扫描技术,因为同时进行可以减少检验时间,直到病患的肿瘤分期确定。

Combined Scan for Accurate Tum

By Zosia Chustecka
Medscape Medical News

December 5, 2006 ??The staging of colorectal cancer could be made easier for both patients and doctors by using a one-step procedure combining 2 imaging procedures, suggests a preliminary study in the December 6 issue of the Journal of the American Medical Association.

The small study showed that a whole-body scan with combined positron emission tomography (PET) and computed tomography (CT) in a single session was less time-consuming and was "at least equivalent" to the conventional stepwise use of these procedures. It also showed that the single combined scan was more accurate than CT alone, which is the most common method used for tumor staging in colorectal cancer.

"Combined PET/CT colonography has the potential to advance as the first-line diagnostic tool for staging colorectal cancer," senior author Gerald Antoch, MD, from Essen University Hospital, Germany, told Medscape. He added, however, that this study is preliminary and "large patient cohorts are required to verify our results."

More Accurate Than Conventional CT Scans

Dr. Antoch and colleagues conducted the study in 47 patients who had already been diagnosed with colorectal cancer by optical colonoscopy and clinical signs. Colonoscopy is currently the reference standard for detecting colon cancer, but obviously, it offers a view only from within the gastrointestinal tract, the researchers comment. The next step in the process ??imaging to see whether the cancer has spread to the lymph nodes and/or to solid organs ??is usually carried out by CT of the abdomen and thorax.

The study showed that this conventional route, using CT alone after colonoscopy, was significantly less accurate in tumor, nodes, metastases (TNM) staging than the new approach of the combined PET/CT scan (22% difference; P = .003).

The results of the combined PET/CT scan changed therapy management in 4 patients (9%), the researchers report. The change was based either on a more accurate assessment of the tumor stage of colorectal cancer or on finding of further tumors ??1 patient had a hepatocellular carcinoma in addition to liver metastases, while another was found to have a thyroid carcinoma (falsely interpreted as goiter on CT alone).

At present, after the CT scanning, if the findings are inconclusive, some patients are sent for a further scan by PET. The authors point out that while this multistep procedure is conventional, it is not recommended for routine use in clinical staging guidelines, and neither is the new single-step combined PET/CT scan that they were using.

When the researchers compared these 2 procedures (ie, CT scan followed by PET scan vs combined CT/PET scan in 1 session), they found no significant differences in the accuracy of TNM staging. They point out, however, that the single-step procedure is less time-consuming, provides the referring physician with a single report, and "represents a psychological and physical advantage" to the patient.

The fact that combined PET/CT colonography offers whole-body colon cancer staging in a single session obviates the need for the traditional multistep multidisciplinary staging algorithm, Dr. Antoch commented to Medscape. The traditional algorithm may include ultrasound, CT scans of the abdomen and/or thorax, chest x-rays, and PET scans, and these multiple examinations require substantial time, he noted.

Combined PET/CT scanners have been available since 2001, and there are currently approximately 2000 machines installed worldwide, Dr. Antoch said. The PET/CT-colonography procedure described in the paper requires a special imaging protocol that involves a water-based enema to distend the colon, and he hopes that this protocol will be adopted by the other sites.

Dr. Antoch said his team has already integrated the PET/CT-colonography protocol described in the paper into daily clinical practice. "Patients with an initial diagnosis of colorectal cancer undergo PET/CT colonography as the only staging examination following optical colonoscopy," he said.

Dr. Antoch also told Medscape that he would urge fellow clinicians with access to such combination scanners to do the same, as the single procedure reduces the time until the patient is completely staged.

JAMA. 2006;296:2590-2600.

    
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