In 2007 a press report stated that there was a direct relationship between microchips and certain tumors in mice, rats, and dogs. Depending on the studies reviewed, tumors happened in anywhere from 1-10% of the animals who had chips implanted. This article has caused an uproar and concern in those who have read it. Now there are people who are extremely concerned that microchips will cause tumors in their pets.
However, I haven't seen any good evidence that this is a true risk. Here are some quotes from the original article, which I think are overlooked in the discussion.
Dr. Cheryl London, a veterinarian oncologist at Ohio State University, noted: "It's much easier to cause cancer in mice than it is in people. So it may be that what you're seeing in mice represents an exaggerated phenomenon of what may occur in people."
Tens of thousands of dogs have been chipped, she said, and veterinary pathologists haven't reported outbreaks of related sarcomas in the area of the neck, where canine implants are often done. (Published reports detailing malignant tumors in two chipped dogs turned up in AP's four-month examination of research on chips and health. In one dog, the researchers said cancer appeared linked to the presence of the embedded chip; in the other, the cancer's cause was uncertain.)
A Time article had more interesting quotes.
In an exclusive interview with TIME, Silverman provided a list of 34 studies the company included in its FDA application, including one of the three mentioned in the AP article, which showed that less than 1% of 4,279 chipped mice developed tumors "clearly due to the implanted microchips" but were otherwise healthy, and that "no clinical symptoms except the nodule on their backs were shown." The second study, conducted in France in 2006, two years after VeriChip's FDA application was approved, found that while 4% of the 1,260 mice in the study developed tumors, none of them were malignant. As for the third study, Silverman says it was conducted in mice specifically bred to produce tumors, and was therefore omitted from the sheaf of studies included in the FDA application.
Dr. Lawrence D. McGill, a veterinarian and leading expert in animal pathology says the tumor development in rodents is unsurprising. "Even if you put in a bland piece of plastic, it will produce tumors in rats and mice," says McGill, who assessed the studies on behalf of VeriChip. He says it would be a leap to apply the findings of studies in mice to cats or dogs — or to humans, for that matter — which are much more complex animals. Few official scientific studies have been conducted on the effects of microchip implants on house pets, but none have found a link between the chips and cancer, says McGill. If there were a problem, he says, we would have already seen lots of cancer among the approximately 10 million pets that have been chipped over the past 15 years. Says Silverman, "There are no reported incidents to the FDA of any cancer formation around that."
The American Veterinary Medical Association did release a position statement shortly after the original article came out.
In a Sept. 13 statement posted online, the AVMA said staff and member veterinarians are actively looking into the potential for electronic identification implants to induce tumors in dogs, cats, or people but must await more definitive data and test results before taking further action.
Considering how a large number of pets have been implanted with microchips with a relatively small number of confirmed cases of tumors associated with microchips, the AVMA advises against a rush to judgment on the technology.
In fact, there is a concern among veterinary medical researchers that some of the research into supposed chip-induced tumors may be flawed, because the animals used were genetically predisposed to cancer. In addition, removal of the chip is a more invasive procedure and not without potential complications.
The Time article further quotes a representative of the AVMA.
The AVMA officially counsels against removing the chip, while assuring pet owners it will continue to monitor the situation. "At this point we do not recommend that people should stop microchipping," says Dr. Rosemary LoGiudice, a veterinarian and assistant director with the AVMA. "We are actively watching. For the number of animals that are said to actually have microchips, when you consider the number of animals that have been microchipped and returned to their owners, the benefits are huge compared to the few and suspect cases that have been reported to have tumor formation."
Personally, I don't think there is a large enough risk of tumors to be concerned. Is the potential there? Quite possibly. However, there really is nothing out there without any risk at all. Vaccines, routine surgeries, antibiotics...they all carry some risk. Some time read the warnings and side-effects on a label of ibuprofen or aspirin, and you may be surprised and scared. No matter what medicine we take or procedure we undergo, there will be various degrees of risk. Thankfully, most of the time nothing adverse happens. So there could be minor risk in some patients, but I see no evidence that it's a worry for the majority of pet owners.
In my years of practice I have never seen any tumor associated with a microchip or talked to any other vet who has seen it. Millions of pets and livestock world-wide have received microchips, yet there are no reports of wide-spread tumors. In fact, this one 2007 article is the only I've ever heard of that has looked into the issue, and if it was really a true concern, I would think that more data would have come out in the three years since it was published.
I know that there are some people who are vehemently opposed to microchips, and I'm sure that I won't convince them otherwise. But based on the available data I think that microchips are overall safe. I recommend them to my own clients, and believe in them enough to implant them in my own pets.