ESTES PARK, Colorado (EGMN) –The biggest chunk of the substantial mortality benefit conferred by bariatric surgery comes not from reduced cardiovascular mortality or diabetes-related deaths, but from fewer deaths due to cancer, according to two large studies of about 20,000 subjects.
The impressively large relative risk reductions in diabetes-related and cardiovascular mortality following bariatric surgery have garnered much attention. But obese individuals have an increased risk of cancer, and the absolute number of cancer deaths avoided following the surgery overshadows deaths due to the other causes, Dr. Daniel Bessesen explained at a conference on internal medicine sponsored by the University of Colorado.
“It has been thought that insulin binding to insulin-like growth factor might promote cancer. People have wondered, if patients lose weight and their insulin levels go down, could this prevent cancer? The data from these two studies suggests so,” observed Dr. Bessesen, professor of medicine at the university and chief of endocrinology at Denver Health Medical Center.
The Swedish Obese Subjects (SOS) study was a prospective, nonrandomized study involving more than 4,000 obese individuals, half of whom underwent gastric bypass surgery by general surgeons in Swedish community hospitals.
The surgery patients had an adjusted 29% decrease in overall mortality at an average 10.9 years follow-up, compared with matched controls. There were 13 fatal MIs in the surgery group, compared with 25 in controls. Even more impressive, there were 29 cancer deaths in the surgery arm, compared with 47 in controls (N. Engl. J. Med. 2007;357:741-52).
The other major study was a retrospective cohort study involving 7,925 obese Utah residents who underwent gastric bypass surgery and an equal number of matched controls who did not have the surgery. At 7.1 years of follow-up the adjusted mortality was 40% lower in the surgery group.
Once again, the biggest absolute benefit was in reduced cancer deaths. The relative risk of death due to cancer was 60% lower in the surgery group, with a rate of 5.5 deaths per 10,000 person-years, compared with 13.3/10,000 person-years in controls. Deaths due to coronary artery disease fell from 5.9 to 2.6/10,000 person-years, a 56% reduction, while diabetes-related deaths dropped by 92% from 3.4 to 0.4/10,000 person-years (N. Engl. J. Med. 2007; 357:753-61).
Both the Swedish and Utah investigators have recently expanded upon their findings via follow-up studies. The Utah investigators used the Utah Cancer Registry in looking at 6,596 patients who underwent gastric bypass surgery and 9,442 severely obese individuals who did not. During a mean 12.5 years of follow-up, the total incidence of cancer was 34% lower in the surgery group. Cancer mortality was 46% lower (Obesity [Silver Spring] 2009;17:796-802).
The Swedish group reanalyzed the SOS data in terms of the incidence of first-time cancer. They found a 42% decrease during 10 years of follow-up in women who had bariatric surgery, but no significant reduction in men (Lancet Oncol. July 2009; 10:653-62).
In addition to the reduced risk of death, what other benefits can obese patients realistically expect from bariatric surgery? Dr. Bessesen said gastric bypass – the most popular and effective form of bariatric surgery – consistently achieves roughly a 30% weight reduction, or 50%-60% loss of excess body weight, and this has been maintained at follow-up now stretching out beyond 15 years. Laparoscopic adjustable gastric band surgery, which is less invasive and less risky, is also less effective, conferring about a 20% weight reduction.
“Laparoscopic band results are variable depending on surgeon expertise. A really good surgeon will get 25% weight loss, an average surgeon more like 16%-18%. Roux-en-Y gastric bypass weight loss results are more consistent,” he said.
Sleep apnea is improved in almost all affected patients after bariatric surgery. So are gastroesophageal reflux, urinary incontinence, and hyperlipidemia. Diabetes is resolved after gastric bypass in 80%-85% of affected patients, and in 60%-70% after laparoscopic adjustable gastric banding. Hypertension is the comorbidity most resistant to resolution; only about half of patients are eventually able to stop their antihypertensive medications after bariatric surgery, Dr. Bessesen continued.
As for the risks of bariatric surgery, with improved surgical techniques the 30-day mortality of gastric bypass has dropped to about 0.5%, with 1%-2% mortality at 2 years. In contrast, the long-term mortality of laparoscopic adjustable gastric banding is only about 0.1%; however, this procedure entails the inconvenience of many follow-up adjustments. Pulmonary embolism, wound dehiscence and infection, anastomotic leaks, and anastomotic stricture are potential complications of bariatric surgery. And about 10% of patients fail to lose substantial weight after bariatric surgery; to date there’s no way to identify them in advance.
“It’s just a risk you take,” Dr. Bessesen concluded. “This is big-time surgery: big benefits, big risks.”
Copyright (c) 2009 Elsevier Global Medical News. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
科罗拉多州埃斯特帕克市（EGMN）——据2项对大约20,000位受试者进行的大宗研究结果显示，减肥手术带来的实质性死亡获益在很大程度上不是来自于心血管死亡率或糖尿病相关死亡率的下降，而是由癌症死亡例数减少所产生。
Daniel Bessesen博士在科罗拉多大学主办的内科会议上解释道，肥胖手术后糖尿病相关死亡和心血管死亡的相对风险大幅下降，这已引起了广泛关注。不过，肥胖个体癌症发病风险增加，手术后因癌症死亡的绝对例数使因其他原因死亡的例数显得微不足道。
据美国丹佛医学中心大学医学教授兼内分泌学主任Bessesen博士观察，“大家一直认为，胰岛素与胰岛素样生长因子相结合可诱发癌症。人们质疑，若患者减重且其胰岛素水平下降，这样是否可以预防癌症发生呢？这两项研究的数据表明确实如此。”
瑞典肥胖受试者（SOS）研究是一项前瞻性、非随机研究，肥胖受试者逾4,000例，其中半数由瑞典社区医院的普外医生进行了胃旁路手术。
与匹配的对照组相比，肥胖手术组患者在平均10.9年的随访期内整体死亡率下降29%（调整后的）。手术组有13例致死性心肌梗死（MI），而对照组有25例。更为值得关注的是，手术组发生了29例癌症死亡，而对照组则发生了47例(N. Engl. J. Med. 2007;357:741-52)。
另一项大型研究是一项回顾性队列研究，纳入的7,925例受试者为犹他州肥胖居民，其中半数进行了胃旁路手术，半数是未进行此手术的匹配对照。在随访7.1年后，手术组调整后的死亡率较对照组降低40%。
无独有偶，最大的绝对获益为癌症死亡人数减少。手术组癌症相对死亡风险下降60%，死亡率为5.5 /(10,000人•年)，而对照组为13.3 /(10,000人•年)。 冠状动脉疾病所致的死亡由5.9/(10,000人•年)下降至2.6/(10,000人•年)，降低56%，而糖尿病相关死亡由3.4/(10,000人•年)下降至0.4/(10,000人•年)，降低92% (N. Engl. J. Med. 2007; 357:753-61)。
近期，瑞典和犹他州研究者通过进行随访研究对其先前的研究结果进行了扩充。犹他州研究者利用犹他州癌症注册处资料，随访了6,596例进行了胃旁路手术的患者和9,442例未进行手术的重度肥胖患者。在平均12.5年的随访过程中，手术组的总体癌症发生率和癌症死亡率分别较未手术组降低34%和46%(Obesity [Silver Spring] 2009;17:796-802)。
瑞典研究小组在首次癌症发生率方面对SOS数据进行了再次分析。他们发现，在10年随访过程中，进行减肥手术治疗的女性首次癌症发生率下降42%，而在男性中则无显著下降(Lancet Oncol. July 2009; 10:653-62)。
除了死亡风险下降外，肥胖患者实际上还可以从减肥手术治疗中期待其他哪些获益呢？Bessesen博士指出，最普遍且最行之有效的减肥手术——胃旁路手术，可实现体重减少大概30%，而超重患者体重可减少50%～60%，在随访期延长至15年以上时，这种减少程度仍持续存在。腹腔镜可调节胃束带术为创伤性较小且风险较小的手术，疗效亦稍逊，可使体重减少大约20%。
“腹腔镜胃束带术结果不一，视术者的技术水平而定。一位手术技术确实很好的术者可使体重减少25%，一般的术者减少程度大概为16%～18%。Y型胃旁路减肥术的效果则更具一致性，”他说道。
Bessesen博士继续说道，几乎所有的肥胖患者在减肥手术治疗后睡眠呼吸暂停均有所改善，胃食管反流、尿失禁以及高脂血症均如此。胃旁路术后有80%～85%的肥胖患者糖尿病获得缓解，而腹腔镜可调节胃束带术后缓解率达60%～70%。高血压并发症最难获得好转；减肥手术后仅大概半数患者最终能够停用抗药血压药。
在减肥手术的风险方面，外科手术技术水平提高可使胃旁路手术30天病死率降低至大约0.5%，2年时降低至1%～2%。相比之下，腹腔镜可调节胃束带术的长期病死率仅为0.1%左右；然而，这个手术也存在许多随访期调节不方便的情况。肺栓塞、伤口裂开和感染、吻合口漏以及吻合口狭窄均为减肥手术潜在的并发症。大约10%的患者在减肥手术治疗后未能实现体重大幅减少，至今仍无法提前对这类患者进行识别。
“这本身就是在冒险，”Bessesen博士总结道。“这属于一流手术——大获益，大风险。”
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