Friday, June 27, 2008

Bariatric surgery slashes cancer risk?

Latest news - front page for several days - has been that having a gastric bypass can cut cancer risks.

Bariatric surgeons at McGill University compared the records of 1000 patients mostly gastric bypass to 5700 people matched by age, weight and sex who did not have the surgery.

In the surgical group, 2 percent developed cancer and in the non surgical group, 8.5 percent developed cancer.

Although the study is yet unpublished, these bariatric surgeons presented their preliminary findings at the latest meeting of bariatric surgeons of the ASBMS recently. (talk about preaching to the choir).

And isn't it amazing that an unpublished study has made such headlines for several days now?

What is even more amazing is that while Dr Glenn Gaesser found in his metastudy that obese people were 40 percent less likely to develop cancer, how these surgeons found the opposite. Of course 6 percent more cancer isn't really that great although you can express it to sound amazing as MSNBC did .... saying 80 percent greater chance of cancer in the non surgical group.

One of the objections to this study was actually brought up by another bariatric surgeon. Edward Phillips, a bariatric surgeon at Cedars-Sinai Medical Center told the LA Times that patients who have weight loss surgery, are often screened for cancer before surgery. "We may be selecting patients who don't have cancer for surgery, thus biasing the study", he said.

It's hard to judge without seeing the study. For example, a lot of very obese people are yo yo dieters and that weight cycling raises all health risks. Also I am wondering why they had to pick so many obese people to compare. Why not select 1000 fat people to match up with the 1000 WLS patients? Because I bet in 1000 fat people you might not get any cancer at all and that wasn't what they wanted to prove with their study.

The study only ran for 5 years and critics of the study have pointed out that it often takes a cancer many more years to develop than that and that had the study been taken out longer, the results might have been different.

Breast cancer was one of the cancers which they saw less of in the bariatric patients. Could it be that after a gastric bypass, patients were unable to take birth control medication (a major risk factor for breast cancer - that is medications work differently in gastric bypass patients because of the malabsorption issues)? Or that the gastric bypass patients were unable to eat or digest foods with transfat in them (another cancer activator). Also most weight loss surgery surgeons require their patients to quit smoking whereas the fat controls were not necessarily non smokers. Another thing is that most gastric bypass patients can no longer drink alcohol especially the newer ops as they would have been looking at, if the study only ran 5 years - alcohol can be another risk factor for cancer.

There are just too many other factors which could be operational in all of this to assume that it was the surgery and weight loss which explained the 6 percent less cancer in the surgical group.

For example, most gastric bypass patients are told to exercise often in order to help keep off the weight. Exercising can knock the risk of cancer (in anyone of any size) down, 40 percent. Most of the obese controls were probably not exercising regularly.

Ideally the fat controls should have also been matched for exercise, not smoking and dietary modifiations (like the elimination of trans fat in the diet) if the scientists wanted to really see if it was the surgery or the weight loss which explained the less cancer in the surgical group.

A non randomized study always raises red flags. The fat people could have been picked for their cancer risk (i.e. cancer in the family etc).

I guess the thing which rather annoys me about this whole deal (besides the news media making it a headline for the last week or more) is that all the research I've done comes out the opposite...

  • Cancer is seen 40 percent less in fat people than in slim people - it has been considered a disease of the slim and yet now they are trying to link it like everything else to obesity.
  • Two oncologists have told me that fat people if they get cancer, are much more likely to survive than slimmer people.

So unlike the media is trying to tell us, the "link between obesity and cancer" has not been well proven at all. On the contrary. The American Cancer society has stated that lifestyle (not girth) is a factor in 85 percent of cancers.

Even the release form for gastric bypass used by many surgeons and usually attributed to Kaiser Permanante warns:

Keep In Mind: Slender individuals have adult diabetes. Slender individuals have heart attacks. Slender individuals develop arthritis and have joint problems. Slender individuals have strokes and develop cancer. If obese individuals have these problems more commonly than the slender, it is because the same bad health habits just don't happen to cause obesity in some individuals "fortunate" enough to be slender no matter what they eat. They may be slender but they could very likely die just as early in life as someone who is overweight.****

And obviously those who wrote this release form do believe in bariatric surgery.

Additionally, I have seen many get cancer who were very slim. Some of them were very fit like a 53 year old family member. She ran marathons and I'm sure the last time she visited her doctor before she came down with the cancer which was to kill her 3 years later, her doctor proclaimed her totally healthy, at her perfect weight with low risk numbers.

So much for the risk numbers and perfect weight predicting protection against cancer!

I would not take this one to the bank. Many gastric bypass patients can develop a condition called "leaky bowel" wherein bacteria, not killed in stomach acid, enter the small gut and are absorbed along with the food. With this condition causing in many, auto immune disorder like RA and lupus, it is suspected that the immune system of a gastric bypass patient might been impaired by the surgery and not strengthened as these McGill bariatric surgeons would like us to believe.


cynth said...

Bariatric surgery cuts your cancer risk because you die before you have time to develop cancer. This would be the only stat I would believe.

The media will print anything these days as long as it gets attention.

Stef said...

Uh ... is it maybe possible that WLS patients *die* before they get old enough to get cancer?

Unknown said...

They also didn't bother to control for race or socioeconomic status. Because of our country's racial problems and the way that race plays into financial well-being, as well as the ways in which being poor causes people to live in areas with environmental issues, etc, black people and poor people tend to end up with more cancer. WLS recipients are almost exclusively white, and by definition not poor -- what poor person can afford not only the surgery, but the recovery off work?

In other words, this may be just another study showing us what we already knew: poor people are more likely to get cancer, and especially more likely to die from it.