Meditations of an oncology geek

Archive for August, 2011

Do taller women get more cancer?

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27 August 2011

Cynthia Davis from Paradise, CA writes:

Since my daughters and I are tall, could you work on this, please? http://www.clinicalresearchsociety.org/2011/07/22/cancer-more-prevalent-in-taller-women

The study referenced in the linked article is this one (1)

The authors of the study, lead by Jane Green, compiled data on 1.3 million women in the UK and found that women taller than 5’9″ have a higher incidence of various forms of cancer. Unlike many of the cancer risk association articles I have commented on in the past few months, the statistics in this study appear fairly robust. I could not find an obvious conflict of interest, nor could I find obvious flaws in their methodology.

I would like to point out that this study is a correlation study, not a causation study. From this study alone it is impossible to determine if taller stature leads to a higher incidence of cancer, or cancer leads to taller people. Though I would argue for the former rather than the latter, I feel it would detract from the take-home message.


Image: a recent study suggests that exceptionally tall women develop cancer more frequently than most.

If it is a given that taller people will develop cancer with higher incidence than others, the next question to ask is: what can an individual do about it?

One has about as much control over how tall they are as, say, the color of their eyes. One could willingly make oneself shorter by amputation or auto-mutilation, but such acts would likely not have an effect on the underlying biological mechanisms.

In a previous article I commented on the aura of hysteria surrounding things that “cause cancer.” If we accept that some things are simply out of our control, there are a few things that that are BEST to spend mental and physical energy on. These include mitigating sun exposure and smoke inhalation, as well as maintaining a healthy weight and a good dialogue with a primary care physician.

I would like to link a previous article on cancer prevention where I discuss several active means of mitigating cancer risk.

If you’re concerned about developing cancer at a younger age, talk to your doctor and see what types of screening he or she can do. At the very least, starting a dialogue about the topic with a health care professional will help alleviate undue stress and improve mental well being and quality of life.

Ryon

Reference:
1) http://www.ncbi.nlm.nih.gov/pubmed/21782509

Written by Ryon

August 28th, 2011 at 8:49 am

Posted in Science Blog

Does aspartame cause cancer? Do you eat a pound of aspartame per day?

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20 August 2011

Caitlin Bigelow of San Diego, CA writes:

My mom and I have had a few heated discussions on the health effects of diet soda. It came up yesterday when she purchased enough diet soda to drown a small child. I’m curious, do artificial sweeteners like sodium cyclamate and aspartame cause cancer? And if so in what quantities would you need to consume them for it to be a factor?

Cheers,
Caitlin

Hi Caitlin,

Because sodium cyclamate is banned in the US (a controversial topic in itself) I will chose to discuss Aspartame for this article.

Aspartame is an artificial sweetener first synthesized in 1965 and approved by the FDA in 1974. It is ubiquitous in its use as a food sweetener in the US.

There are many reviews of scientific literature that suggest that aspartame probably does not cause cancer, and it is the current opinion of the FDA that it is safe (1).

Correlation and Causation:

A recurring theme in this blog is the distinction of correlation and causation. A correlation study would be one where the amount of aspartame consumed by individuals in a group was followed for some length of time, and their cancer rates recorded. Established statistical methods and universally accepted (yet arbitrary… but that is a topic for another time) thresholds are used to establish correlation. An example of this would be this one from 2007 in Italy of over 7,000 cancer patients and 7,000 matched controls (2). Although some ways of chopping up the data might indicate an association for a few types of cancer, the overall result appears to suggest no consistent association between aspartame consumption and cancer incidence.

An example of a causation study would be experimental in nature. Say, one was to feed mice aspartame (or not) for their lifetime and detect their cancer rates at a certain time point.

Actually, that is exactly what a group from Milan, Italy did in 2010 (3). The group found roughly a 20% increase in the rate of liver and lung cancers in mice fed the equivalent of 3900 mg/kg of body weight per day. Pound per pound, corrected for the faster metabolism of rodents, that amount is about the equivalent of 2/3 of a pound of aspartame for an 150lb human per day. A 12oz can of aspartame-sweetened soda often contains 0.0004 pounds of aspartame.

There are also numerous studies that report no such induction of tumors in a high aspartame diet (4).

Under extreme conditions aspartame might help promote cancer. Consumption in ranges that more accurately mirror dietary habits of humans do not see any measurable effect. Studies do not show any trends affecting the cancer rates in humans.

Ryon’s verdict: Based off of available epidemiological data and experimental models, aspartame appears to not cause cancer in humans.

References:
1) http://www.ncbi.nlm.nih.gov/pubmed/17828671
2) http://www.ncbi.nlm.nih.gov/pubmed/17043096
3) http://www.ncbi.nlm.nih.gov/pubmed/20886530
4) http://www.ncbi.nlm.nih.gov/pubmed/17828671

Written by Ryon

August 19th, 2011 at 8:50 am

Posted in Science Blog

Cancer sniffing pooch?

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13 August 2011

This week’s question comes from Mitchell Vamos in La Jolla, CA:

I haven’t heard much lately about the cancer-sniffing dogs. Will we one day be able to skip the biopsy and just get sniffed by a pooch?

Writing this blog often follows a predictable pattern:

1) Someone asks a really off-the-wall question about some new cancer “cure” or radical prevention protocol.
2) I look into the actual papers (if there are any) and comment on the research.
3) The papers (or lack thereof) are often heavily flawed, or the media has completely mis-represented the results.

I initially felt a sense of banality or fatalism when researching cancer-sniffing dogs. I had heard of this in passing a while back, but the data at the time was not all that convincing, and had all been produced by one laboratory. That was in 2006.

To my amazement, there has been better science performed on the topic in the last few years. In November 2010 a group in Sweden released a study on cancer detection using dogs trained to smell tumors. (1) Giant Schnauzers (right) were trained to distinguish the blood of recently diagnosed ovarian cancer patients compared to healthy controls. The group reported an extremely high rate of accuracy for the cancer-sniffing pooches. If taken literally, these results would indicate these dogs as better than most early detection screens currently available for ovarian cancer!

There are other studies that have claimed success training dogs to recognize the breath of breast and lung cancer patients (2) and others in detecting bladder cancer from urine samples (3) but their results were not as accurate as current diagnostics. Granted, current diagnostics are both more expensive and invasive than letting a pooch give your face a sniff. One could imagine the low cost leading to more widespread screening.

Now, this might not apply across the board, as other studies using dogs to detect breast or prostate cancer in urine samples did not hold up (4).

I’d be really curious to see if other groups can independently train dogs to accurately detect ovarian cancer from blood samples. If so, it would imply that there are yet undiscovered factors in the blood of ovarian cancer patients (and possibly other types of cancer as well) that can be used as diagnostics for early cancer screening! yay!

I could envision several problems for scaling up cancer detection by dogs. The first of which is it is not possible to have two identical dogs, identically trained, and the subjective nature of professional dogs diagnosing cancer patients means the vetting process might be tricky. Bomb-sniffing dogs are trained in consistent faux settings with explosives hidden at the scene. It would not be feasible to give people cancer just to test the tumor-sniffing pooches. Though I could imagine ways to get around this… it would be tricky. Could you imagine having resident dogs in hospitals? As a researcher working in a hospital environment, I would personally love to have a canine co-worker. Though I might be biased… I grew up with big dogs around!

There is something else that caught my intrigue about these studies. If the dogs are accurately smelling something in the blood, urine, or breath, it might be possible to isolate whatever it is they are smelling and use that for a less subjective diagnostic that doesn’t have bad breath and need to be trained. But then again, it could be a balance of multiple factors the dogs are smelling.

Regardless, this area of research might actually lead to real impact on cancer patients. I’ll be following it with great interest.

-Ryon

References:
1) http://www.ncbi.nlm.nih.gov/pubmed/21106067
2) http://www.ncbi.nlm.nih.gov/pubmed/16484712
3) http://www.ncbi.nlm.nih.gov/pubmed/15388612
4) http://www.ncbi.nlm.nih.gov/pubmed/18199013

Written by Ryon

August 13th, 2011 at 9:32 pm

Posted in Science Blog

Do we all have some level of cancer?

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6 August 2011

This week is part II of an article inspired by Anne Kenworthy:

What does it mean to have a “normal” cancer marker? Does this mean we all walk around with some level of “cancer” in our bodies and this is the acceptable level? What’s going on?

Each of us is made up of trillions of cells. According to cell death and renewal expert Dr. John Reed of the Sanford-Burnham Medical Research Institute, every day 50-70 billion cells purposefully undergo cell suicide and are replaced by new, healthy cells. It is this equilibrium of death and renewal in our tissues that keeps us young. This process is also a key defense mechanism against cancer. When a cell begins to go on the road to becoming cancerous (see hallmarks of cancer article) the surrounding cells or immune system will usually detect this progression and send signals to tell the offending precancerous cell to die. This process is called: apoptosis. Defects in this process can lead to cancer in both experimental models and in rare genetically heritable forms of the disease (1). And, most common cancer drugs exploit this mechanism to help a patient battle the disease.

I have seen mathematical models that suggest that each of us starts to develop cancer several times a day! The regular equilibrium of death and renewal in our tissues usually keeps new cancer in check. As we get older, this turnover slows. This is one hypothesis for why cancer is an age-related disease. An unlucky roll of the dice combined with a very, very, very, rare event is required for cancer to arise. The older one is, the more often the dice are rolled. And yes, some people do get cancer at younger ages as well.

This area is somewhat murky for experimental science. It is hard to detect, or to model these events in the body. It is nearly impossible to tell if someone had a pre-cancer that spontaneously regressed, especially if said person never had any symptoms and went about a normal life without ever seeing a doctor and taking a body scan.

So, it IS actually possible that many of us walk around with some undetectable level of cancer. But, low levels of “tumor” markers are not necessarily indicative of cancer. And, it is not a good use of mental energy to worry about it nonstop, as one has about as much voluntary control over these processes as, say, the rate of digestion in your gut or your sleeping heart rate. If one is at risk of developing cancer or relapsing, regular check-ups combined with healthy dialogue with a medical doctor is a good bet to promote physical and mental wellness.

Best,
Ryon

Written by Ryon

August 5th, 2011 at 10:02 am

Posted in Science Blog