A breast cancer survivor shares her experiences with the BRCA gene.

Thursday, May 21, 2009

The Truth Behind Cancer Studies

I typically get an eye-roll from my oncologist whenever I present her with a ripped out newspaper article about a just-released study announcing new cancer findings.

With all the health news accessible these days, you'd think we'd be medical experts. But, in reality, the opposite is true because so much information that's reported is confusing and even incorrect.

How do you know which studies are valid? The starting point is understanding how health-related research is conducted, so I tapped my trusty source, Greg Orloff, who teaches the cancer of biology at Emory University in Atlanta, and has an award winning website about cancer (cancerquest.org).

"There's always an element of sensationalism in the media because that's how they sell their publications," Orloff says. "Consumers need to be able to interpret a study so they can factor this information into their decision-making."

He suggests the following to determine a study's validity:

1. Determine the study's purpose. Orloff says it's expensive to follow 20,000 people over 20 years.

"As a result, researchers attempt to extract as much information from a study as possible and then use the findings for multiple purposes."

A study may be designed to find out one piece of information (whether smoking increases the risk of lung cancer), but other researchers can re-analyze the same data asking different questions and come up with additional conclusions (smoking causes an increase in heart attacks).
"You need to look at the information collected and make sure that researchers are isolating the information you're interested in from other study conclusions. This is difficult to accomplish -- it's hard to analyze one single thing because humans are complex. It could be something other than what's being studied that's contributing to the outcome."
For example, let's say you're looking at the effect exercise has on breast cancer. You conduct a study involving 2,000 people and look at those who exercise 5 times a week, those who exercise 1-3 times a week, and those who don't exercise at all.
Then, you observe the rate of breast cancer occurrence over time. You may find that those who exercised 5times a week had fewer occurrences of breast cancer than those who didn't exercise at all.
But what do you think the chances are that people who exercise a lot also have a healthier diet than those who don't? So another factor -- diet, which is not what the study is about - may play a role in the study's results.
It's a matter of asking the right questions about the study.
2. Look at how the study was designed and conducted. To interpret the findings of a health-related study, consumers need to understand the nature of research and what it entails. Consider the following questions when giving credence to a study:
* How reliable is the information gathered from the participants? People can make mistakes (or not tell the truth) in recalling lifestyle choices and their family health history. This can affect a study's outcome.

* How many people did the study involve? The larger the study, the more credible the information. If the study was not conducted on a large enough population, then you should hold off making a conclusion.

* What was the length of time it was conducted? The results will differ significantly from a 5-year study versus a 20-year one.

"Often, evidence is derived from the preliminary stage -- such as 3 years into a 20-year study -- which can be misinterpreted and hyped by the press, eager to report the latest news. A longer study is better at providing the actual outcome."

* Who participated in the study? Socioeconomic and cultural variations between one population and another can impact results. A study should represent the larger population in order for researchers to make a general, relevant statement. But this is difficult to achieve.

"The challenge is how do you randomly select a population to study? Let's say you decide to study people living near a major college campus. But the problem is that a better-educated, higher-income population lives in that area, and that means they make very different lifestyle choices (such as more visits to the doctor) versus the average population. This is just one factor that will produce a bias in the study's results."

* Who conducted the study and what was their motivation? Is it to convince you to buy their product?

3. Know the difference between "correlation" and "causation."

Correlation -- is an association between two things. For example: Men who exercise have fewer incidents of colon cancer. But is it because they exercise, or that they are eating a better diet? The association between exercise and lack of colon cancer is real, but is exercise actually causing these positive results?

Causation--is a factor that leads to a specific outcome, such as smoking causes lung cancer. You can get lung cancer for other reasons, but scientists have proved that mutagens in smoking do cause lung cancer.

People often misuse those terms and misinterpret results, making a conclusion because they assume causation and correlation are the same.

4. Are studies conducted on animals relevant? Since human studies are difficult and expensive, animal studies can be beneficial since researchers know the genetics and can completely control behavior (how much daylight exposure they receive, diet, hours of sleep).

"For want of a better model system, animals are valuable," says Orloff. "People tend to dismiss animal studies, but researchers can still observe the effects of a particular treatment, which could be applicable to humans.

"At the same time, if a treatment works in an animal model, it may or may not work in humans because we're genetically designed differently."

With animal models, you need to ask if the doses that researchers are giving a reasonable amount.

5. Understand the statistics. "Studies ultimately come down to statistics, and most often, reporters and readers don't understand what those statistics mean. Statistics exist for any study with credibility.

"So, if you are interested in pursing a lifestyle change based on a study, you need to know the numbers that support the findings - is it statistically significant?"

Medical journals are a good place to find a study's statistics.

"And even if you can't interpret the data, the more information you can access, the better you are armed to ask the right questions of professionals (your doctor), who can give you the best answers."

So, despite the eye-roll, it's a good idea to check with your doctor regarding information you find in the media. They are the best source about what's true and false.