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增加淋巴結評估無法改善末期大腸直腸癌之偵測

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本帖最後由 lsc0019 於 2009-8-5 00:17 編輯

作者:Roxanne Nelson  
出處:WebMD醫學新聞

  July 22, 2009 — 根據發表於7月外科學文獻的一篇研究,增加淋巴結評估和摘除並不會改善第3期大腸直腸癌的偵測,也無助於辨識哪些病患有陽性淋巴結。
  
  作者們質疑目前移除至少12個淋巴結以進行評估的實務,但是Medscape Oncology訪問的一名獨立專家並不同意,該專家表示,目前的實務應該繼續。
  
  第一作者、伊利諾州Rush醫學院外科副教授Tina J. Hieken醫師解釋,就臨床實務和大腸直腸癌處置來說,醫師們需要瞭解,有多種因素會影響大腸直腸癌切除時的淋巴結數量。而且,根據我們的研究,越多淋巴結不等同於能找到更多可以從輔助化療獲利的第3期疾病患者。
  
  大腸直腸癌外科實務中,至少切除12個淋巴結的量化方法最初始於1990年的世界胃腸道研討會。這項基準後來被多個機構採用,包括美國外科學院癌症委員會、美國臨床腫瘤協會、國家綜合癌症網絡。多家保險公司也採用這項12個淋巴結的界定。
  
  不過,研究作者結論表示,強制摘取至少12個淋巴結作為品質指標或表現的測量,似乎沒有根據。
  
  為了確認跨部門機構在淋巴結取樣和分期上的操作,作者們比較每個大腸直腸癌案例取樣的淋巴結數量,以及採用新的病理取樣指引前後的相關分期。這始於2004年底,當時開始有在大腸直腸癌切除時增加移除淋巴結的趨勢。
  
  雖然兩個研究組的人口統計學、腫瘤和治療變項都相似,後期的病患(2005年之後)傾向比早期(1996至2004年間)年輕(後期平均70歲,早期為72歲),也較多接受腹腔鏡切除(44.6% vs 7.2%)。後期的白人病患也比較少(81.1% vs 95.8%)。
  
  作者們發現,淋巴結數量平均從12.8增加到17.3,其中有53.0%的早期病患(n= 553人),71.6%後期病患(n= 148人)檢查至少12個淋巴結。
  
  【並未增加第3期疾病之偵測】
  儘管淋巴結取樣有改善,第3期病患的比率並未改變(早期為36.9%、後期為32.4%;P= .31)。在陽性淋巴結病患中,N1和N2疾病的比率未變(早期50.5%為N1、49.5%為N2,後期54.2%為N1、45.8%為N2;P= .54)。
  
  Hieken醫師向Medscape Oncology表示,大多數的外科醫師 — 包括一般外科、大腸直腸外科、腫瘤外科— 將繼續對我們的大腸癌病患進行整體的淋巴結移除。我們希望我們的資料將促成品質指標或表現測量的研究,而不是鑽研到底該對每個大腸癌樣本至少摘取幾個淋巴結,將注意力集中在會影響淋巴結數量的影響因素,而非每位外科醫師。
  
  她指出,其他研究無法發現移除較多淋巴結時的存活利益,這項終點在目前這個研究中並未評估。
  
  【不應改變實務標準】
  不過,一名專家認為,不應改變實務標準,仍應建議至少12個淋巴結。紐約Roswell Park癌症研究中心腫瘤副教授Marwan Fakih醫師問道,我們如何看待這個研究對目前建議對所有大腸直腸癌病患取至少12個淋巴結樣本的觀點?我們應忽略顯示淋巴結取樣和存活有關的超過35,000個T3N0大腸直腸癌案例嗎?我們應忽略前溯研究確認改善淋巴結取樣和整體存活關係的資料嗎?
  
  Fakih醫師在為Medscape Oncology提出的獨立評論中指出,目前的研究是比較兩個族群的回溯研究,但這些族群是無法比較的。這個研究因為沒有適當的比較組而有缺陷。
  
  他表示,作者指出的病患人口統計學資料顯示,後期的病患較年輕、種族分布也不同、後期的腹腔鏡手術也比較多。這些差異使得兩個族群並不相當,因此,無法進行交叉比較。
  
  Fakih醫師解釋,其他未報告的病患人口統計學資料,包括篩檢大腸鏡的診斷以及腫瘤差異,有文獻指出,在過去10年,大腸鏡檢查有增加傾向,早期疾病的診斷也相對增加。因此,早期病患比較可能有較末期的有症狀疾病,而後期病患比較可能在篩檢時即診斷。
  
  這種病患特徵上的不均等,可以用來解釋,儘管增加淋巴結取樣數量,而第3期病患仍未增加。他指出,實際上,2005年之後治療的24.4%病患為T0/T1期疾病,2005年之前則是18.8%的病患,因此可證明後期因篩檢而增加了診斷。
  
  研究者宣告沒有相關財務關係。

Increased Lymph Node Evaluation Does Not Improve Detection of Advanced CRC

By Roxanne Nelson
Medscape Medical News

July 22, 2009 — Increased retrieval and evaluation of lymph nodes does not improve detection of stage?III colorectal cancer or identify more patients with positive nodes, according to research published in the July issue of Archives of Surgery.

The authors question the current practice of removing a minimum of 12 lymph nodes for evaluation, but an independent expert contacted by Medscape Oncology disagrees with them, saying that this current practice should be continued.

In terms of their own clinical practice and management of colorectal cancer, clinicians need to recognize that multiple factors can affect the absolute number of lymph nodes identified with colorectal cancer resection, explained lead author Tina J. Hieken, MD, associate professor of surgery at Rush Medical College in Chicago, Illinois. "Also, appreciate that in our study, more lymph nodes didn't translate into finding more patients with stage?III disease who may benefit from adjuvant chemotherapy."

A minimum threshold of 12 lymph nodes as a quality measure for surgical practice in colorectal cancer was first introduced in 1990 by the World Congress of Gastroenterology. This benchmark was subsequently adopted as a quality measure for surgical practice by several organizations, including the American College of Surgeons Commission on Cancer, the American Society of Clinical Oncology, and the National Comprehensive Cancer Network. Several insurers also adopted the 12 lymph node minimum threshold.

However, the study authors concluded that "mandatory harvest of a minimum of 12 lymph nodes as a quality indicator or performance measure appears unfounded."

To determine the impact of a multidisciplinary institutional initiative on lymph node sampling and staging, the authors compared the number of sampled lymph nodes per colorectal cancer case and the associated staging before and after implementing new pathology sampling guidelines. The initiative was started in late 2004, with the intention of increasing the number of lymph nodes removed during colorectal cancer resections.

Although most demographic, tumor, and treatment variables were similar for both study groups, patients in the late period (2005 and beyond) tended to be younger (median age, 70 vs 72 years) than those is the early period (from1996 to 2004) and had more laparoscopic resections (44.6% vs 7.2%). There were also fewer white patients (81.1% vs 95.8%) in the late period.

The authors found that lymph node counts increased from a mean of 12.8 to 17.3, with 53.0% of patients in the early period (n?= 553) and 71.6% in the late period (n?= 148) having at least 12 lymph nodes examined.

No Increase in Stage?III Disease Detection

The proportion of patients with stage?III disease was unchanged, despite the improvement in lymph node sampling (36.9% for the early period and 32.4% for the late period; P?= .31). Among patients who had positive lymph nodes, the distribution of N1 and N2 disease remained unchanged (50.5% had N1 and 49.5% had N2 disease in the early period, and 54.2% had N1 and 45.8% had N2 disease in the late period; P?= .54)

"Most surgeons — be they general surgeons, colorectal surgeons, or surgical oncologists — will continue to perform the same operation with en bloc removal of lymph nodes for our colon cancer patients," Dr. Hieken told Medscape Oncology. "We hope that our data will prompt a search for indicators of quality or performance measures other than an absolute minimum threshold number of lymph nodes removed per colon cancer specimen, and draw attention to factors, other than the individual surgeon, that may affect lymph node count."

Other studies have failed to find a survival advantage with removal of greater numbers of lymph nodes, an end point that was not evaluated in the current study, she added.

Practice Standards Should Not Change

However, one expert feels that there should be no change in the standards of practice, and 12 lymph nodes or more should continue to be recommended. "How do we view this study in light of the current recommendations to sample 12 or more lymph nodes in all colorectal cancer?" asked Marwan Fakih, MD, associate professor of oncology at Roswell Park Cancer Institute in Buffalo, New York. "Do we ignore data from more than 35,000 T3N0 colorectal cancer cases that show a correlation between lymph node sampling and survival? Do we ignore data from prospectively conducted studies that confirm an association between improved lymph node sampling and overall survival?"

Dr. Fakih, who was approached for independent comment by Medscape Oncology, pointed out that the current study is a retrospective study that compares 2 populations, but the populations are not comparable. The study falls short, largely because of the inappropriateness of the comparison groups.

"The patient demographics reported by the authors show a younger age for the [late period], a difference in race distribution, and an increase in laparoscopic procedures," he said. "These imbalances suggest that the 2 populations are not similar and, therefore, a cross-comparison is not justified."

Other unreported patient demographics include diagnosis by screening colonoscopy and tumor differentiation, and there has been a clear documented trend of increasing screening colonoscopies and an associated increase in early disease diagnosis in colorectal cancer over the past decade, Dr. Fakih explained. "It is therefore feasible that the [early-period] patients were more likely to present with more advanced symptomatic disease than the [late-period patients], who were more likely to be diagnosed upon screening."

This type of imbalance in patient characteristics might explain the lack of increase in stage?III patients, despite the increase in the number of lymph nodes sampled. "Indeed, 24.4% of patients treated in 2005 or beyond had T0/T1 disease, [compared with] 18.8% of patients [treated] before 2005, supporting an increase in diagnosis by screening in the intervention group," he added.

The researchers have disclosed no relevant financial relationships.

Arch Surg. 2009;144:612-617.

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