Bow-wow or squeak-squeak?
When it comes to “sniffing” out cancer, it looks like you may have a choice.
New medical research suggests that dogs and mice may just give us the clue to finding cancer early.
An article in the current issue of the online medical journal PLoS One describes the research of a group of scientists in Philadelphia that trained mice to smell the urine of other mice to determine which mice had lung cancer.
And the experiment was a success: the “smeller” mice were able to tell which of the other mice had lung cancer with a fairly high degree of success. Unfortunately, their success was limited to later stage cancers and the very early stage lung cancers were missed.
In the next step of the experiment, the researchers did laboratory studies to look at what are called “volatile compounds” in the urine by analyzing the urine samples on a specialized machine that can identify small quantities of chemicals.
(Volatile compounds are substances that can exist in a liquid and gas phase. So, while they may be contained in urine, once passed out of the body they move into a “gaseous” phase which accounts for their smell. Humans can smell these compounds if the concentration is sufficiently high. However, the amount of these compounds in the body in humans or mice with cancer is probably microscopic, and therefore you need a more sensitive sniffer—like a trained dog or mouse, whose sense of smell is much more delicate than a human’s—to pick up the characteristic odors that may be associated with a cancer.)
The investigators then looked at the results of their chemical analysis, and identified a number of compounds that could have explained the results of the mouse experiment. To their surprise, many of these compounds were found in lower quantities in the urine of mice with lung cancer compared to the mice without lung cancer.
They go on to point out that smell is based on a combination of a number of different compounds, and that lower amounts of a compound may change the smell of the urine just the same as a larger amount of a compound.
Further analysis showed that the researchers could actually plot the differences in the chemical structures of the urine from the mice with and without lung cancer, once again with a reasonably high degree of accuracy.
Their conclusion?
“The data in this paper are consistent with the hypothesis that diagnostically useful volatile compounds are produced in patients with lung cancer and secreted into the urine, thus providing support for this diagnostic approach in the context of lung cancer.”
They also noted that using urine samples for this process is probably a better bet than using breath samples, which has been the approach utilized by some other investigators. And they are moving forward with studies in human patients to determine if these interesting results are in fact applicable in the real world and will help us detect cancer at an earlier stage than currently possible.
This isn’t the first time I have written or commented on this type of research.
I can recall a paper that appeared a number of years ago in a British medical journal that reported—as best I recall—using dogs to sniff urine samples of cancer patients to detect bladder cancer. That experiment was a modest success, and it did get a lot of media attention.
More recently, in another such report dog trainers were able to get neighborhood dogs to sniff breath samples from cancer patients and identify them accurately when compared to breath samples from people without cancer.
When I heard about article #1, I laughed and went on with other business. When I heard about article #2, I actually thought maybe this thing was real after all.
At the time, my comments were generally along the lines of the currently reported research. Namely, is it so far out to believe that a cancer could produce a compound in such small amounts that we humans can’t smell it or identify it, but dogs—with their great sense of smell--may in fact be able to discriminate the minute quantities of volatile compounds present in urine, breath, or other bodily fluids of cancer patients? (If you don’t think dogs have a great sense of smell, you ought to see my “untrained” golden retriever find his tennis ball on a two acre piece of land late at night.)
When I wrote my blog on the topic, I thought I was done with the subject only to have it become one of the most enduring posts on this site. After four years, people are still posting comments on that blog. Obviously, there is a lot of interest in this subject.
So before you start laughing about mice smelling urine samples or dogs smelling breath samples to detect cancer, I would suggest you take a step back and give the idea some serious thought and consideration.
I learned a long time ago never to say never. And when it comes to detecting cancer early by a smell test, well….stranger things have happened.
Gotta go, now. Kobi (my dog) wants me to throw his tennis ball…
