Man's Best Friend, Cancer's Worst Enemy?

Everyone has heard the expression “man’s best friend” when referring to our favorite four-legged pals. But the phrase may take on a whole new meaning in the coming decades, as dogs are enlisted to aid humans in the fight against cancer. Dogs have been used to sniff out explosives and drugs; track criminals; rescue mountain climbers; assist the blind; and warn of epileptic seizures, low blood sugar, and heart attacks—now they may add “detecting cancer” to their resume.

Researchers have suspected for years that canines may have the ability to smell cancer with their incredible olfactory glands, based in part on results from scientific studies that have documented dogs’ ability to recognize chemicals that are diluted as low as parts per trillion (dogs’ sense of smell ranges from 10,000-100,000 times more sensitive than that of humans). The research being done in this area of medicine stems from the theory that cancers (and other diseases) cause subtle chemical changes in the body and alterations to metabolism, which subsequently release a different odor. These studies have shown that dogs are particularly adept at detecting lung and breast cancer, as patients with these two types of the disease emit patterns of biochemical markers when they exhale. There have also been several documented cases of individuals whose cancer was detected after having their seemingly normal moles checked out because their dogs were continually bothering and sniffing them.

In 2004, researchers conducted a study in which six different breeds of dogs of varying ages underwent a seven-month training course to determine whether they could detect prostate cancer by sniffing urine samples. In the final double-blind experiment, each dog underwent nine separate tests in which it was shown seven urine samples and told to lay down next to the cancerous one. The dogs achieved a success rate of 41%—much higher than the 14% anticipated. Although not accurate enough for diagnostic testing, scientists say the results bring us one step closer to being able to identify cancer-specific patterns of chemicals, which could result in a more effective screening process for bladder cancer.

The latest canines to assist in the fight against cancer are the purebreds that compete at the Westminster Kennel Club Dog Show. The benefit of studying these pups is simple: many of the cancers that are a problem for humans, such as melanomas, skin cancers, lymphomas, and leukemias, are also a problem for dogs. With an estimated 10% of dogs in the US contracting some form of cancer each year, and with such a well-documented lineage (each Dog Show participant must have had both parents as registered members, as well as their parents’ parents), these dogs could provide some very significant data with regard to what genetic mutations are responsible for the development of cancer.

The growing field of study known as “comparative oncology” is expected to help both humans and dogs. Dr. Susan Lana, a veterinarian oncologist at Colorado State University, is one of the emerging experts in comparative oncology. She claims that there are several reasons that dogs are such an ideal choice for studying and comparing cancer research (eg, dogs share our environment, breathe the same air and drink the same water.) Another factor is that, like humans, they develop their cancers naturally, as opposed to laboratory rodent subjects that have their cancers given to them.

In fact, comparative oncology has already begun to pay off for humans and dogs alike. Ken Lipmann was a recent patient and recipient of a cancer vaccine that has proven to be very successful in dogs. Lippman was diagnosed with advanced melanoma years ago, and the vaccine is designed to trigger an immune system attack if there is any reoccurrence of his cancer. The vaccine has already been used to extend the lives of dogs up to five years in situations where, without the vaccine, they are estimated to survive for only a few months.

So the next time you are walking Fido, Rover, Duke, or Missy, and they insist on sniffing every stop sign, fire hydrant, and tree in their path, keep in mind that it is this type of behavior which may one day save your life or the life of a loved one. No other animal has ever been worthy of the title “Man’s Best Friend.” Now, if we could only get cats to start contributing…