Electrochemotherapy – A New Way to Treat Tumors in Horses

By Heather Smith Thomas

Some of the most troublesome tumors in horses are sarcoids and melamonas. Most melanomas are benign growths that appear in older gray horses. They may grow large, however, or multiple tumors may appear, interfering with bodily functions or use of tack. Other tumors that can be a problem for horses include squamous cell carcinoma.

There are several ways to treat these, depending on size and location. Common methods include surgical removal, chemotherapy to shrink the tumors, and autogenous vaccines. Dr. Kelly Farnsworth (Washington State University) is using a new method called electroporation (electrochemotherapy) that is proving to be very successful for these types of growths.

This technology enhances the effects of chemotherapy. “By passing an electrical current through the tissue at a certain wave length and pulse rate, it temporarily opens up small pores/channels within the cell walls. This allows fluid or substances to be transferred in and out of the cells,” he says. This makes it easier to get chemotherapy drugs into the tumor cells.

“Many of the drugs we use, like cysplatin, do not cross cell membranes very easily. They have to be actively transported into the cells or go in by diffusion. The electroporation makes little holes that allow chemotherapy drugs to get inside the cells very rapidly. Once they are inside they can exert their effect,” says Farnsworth. These drugs disrupt the DNA and kill the cells when they try to multiply.

The electroporator devices were originally designed in research settings for getting different things inside cells. One use is to help transport viral particles for vaccine development. “Electrochemotherapy was first used 20 years ago, and has gained wider use in human and veterinary medicine in recent years,” he says.

Use of this technique for treating tumors is still relatively new and there aren’t many machines available for veterinary use. “I am sure that in the next few years these machines will be available in other referral centers. We purchased ours through a commercial research group,” he says.

“The first published reports about use in horses came out in Europe, a couple years ago. The first paper demonstrated its efficacy in sarcoids, with a very high success rate,” says Farnsworth.

This may give horse owners one more treatment option. “The main limitation is that we have to get the tumor down to a reasonable size before using this,” he says.

“We often have to debulk a large tumor surgically and then treat the area where the tumor was—because we are treating the area in small, bite-size pieces. We have to be able to pass the electric current through it, so we are limited by the size of the tumor. We recently treated a cat, however, that had a tumor on its side–as big as a potato. When it came back for the second treatment 2 weeks later, the tumor was half that size. After that treatment it was the size of a pea,” he says.

“We are using the same chemotherapy drug, but at a very low total dose. You don’t have to put as much in if you can get it to the right place.” It’s safer for the animal and the people administering the drug.

“But you are passing electrical current through the tissue and must use caution about where you are doing this. The animal is receiving a shock. We’ve done some of the horses anesthetized and some just standing sedated, depending on the location. We’ve done some distal limb tumors with the horse awake, but if the horse’s temperament dictates we anesthetize it briefly. The treatment takes 1 to 5 minutes,” he explains.

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Posted by admin on Feb 27 2013. Filed under Featured, Health & Training. You can follow any responses to this entry through the RSS 2.0. Both comments and pings are currently closed.