Killing Canine Brain Tumors--In-Depth Doctor's Interview
Simon Platt, Professor Neurology & Neurosurgery Service at the College of Veterinary Medicine, University of Georgia, talks about a new clinical trial treating brain tumors in dogs and what that could mean for human patients in the future.
Can you tell us about Gliomas in dogs?
Dr. Platt: Dogs get brain tumors very much like people. In fact, they are so similar that we now believe that dogs can be a great model, if you want to use that word, for evaluating new treatments for people with brain tumors. A lot of treatments that we have in dogs for brain tumors and gliomas, which is one of those brain tumors, cost a lot of money. As such, many owners cannot do the best for their pets and so trials on new drugs (that have been proven to be safe for dogs) are a great way for owners to feel like they are helping their own dog out, and secondarily that ultimately they may be helping people out with the same disease.
How would you treat these types of tumors right now in dogs?
Dr. Platt: Normally we have 3 basic options. We have an option to just give them anti-inflammatory medication, which is the cheapest medication for them, and unfortunately that may only work for about a month or two before the dog starts to change in its personality, vision, and maybe experience seizure activity. We have an option to do surgery, but that becomes very expensive and may only add an extra 5 months or so of a good quality of life before the tumor comes back and starts to show the same signs. Then we have the option of radiation therapy on top of the surgery or on its own.. This last option may only push the quality of life up to 7 or 8 months normally. Surgical and radiation options are obviously expensive and quite invasive in that anesthesia is required and hospital stays are required as well.
If your dog has a tumor like this, will it die?
Dr. Platt: Yes. They are uniformly fatal and the tumors that the dogs have are similar to the worst type of tumors in people where even with the most aggressive therapy, they are ultimately a fatal disease.
Is that why surgery is not always the best?
Dr. Platt: That is right. You cannot just take it out as one well-defined area; bits of it will always remain and it will grow back. This is why radiation is something which can help try to slow down those fingers that are left there from growing back, but they are still uniformly going to be fatal.
For just the inflammatory drugs, how much would that cost?
Dr. Platt: It is probably going to cost about $50 for a month’s worth of treatment.
How much is surgery?
Dr. Platt: Surgery is about $4000.
How much is radiation?
Dr. Platt: Radiation is about $5000.
So radiation and surgery would be $9000?
Dr. Platt: Correct.
Are you only buying months?
Dr. Platt: You are only buying about 8 months of acceptable quality of life with treatment. So you can understand why many people say it is not something that they want to put their dog through and it is not something they can afford.
So this new drug, is it only useful after surgery now?
Dr. Platt: Not necessarily. We decided that we would do surgery and give the drug because we knew that if we did the surgery and the drug did not work we would still be offering some benefit to the owners and to the dogs. If the drug worked, it would hopefully have an additive benefit, which was something I think the owners wanted to hear. Going into a trial and an experiment, like many people will think of it, is going to be a bit scary. They do not want their dog to be experimented on; they want to know it is safe and they want to know potentially that there is a chance it is going to be of benefit. So we could at least say that this is going to be better than nothing, better than anti-inflammatory medication, and maybe it will be better than surgery and radiation together, but that was the unknown.
What is this drug?
Dr. Platt: This is a drug that is already approved in people for certain types of cancer, like colon cancer for instance, and what it actually does is bind to the tumor surface that is feeding on the rest of the body. So, it tries to block the tumor from feeding on the rest of the body and therefore the tumor starts to die off, or that is the theory. The receptors, or the surface of the tumor that feeds on the rest of the body in cancer in the colon looks very similar to the cancer in the brain, and the cancer in the brain in people looks very similar to the cancer in the brain in dogs, so this drug has a chance to shut down the tumor from growing as fast as it would normally.
What is the name of it?
Dr. Platt: It is called Cetuximab. It is a drug that has a few other relatives but it binds to a receptor called endothelial growth factor receptor, and this is something which these tumors express and without them they will not grow.
Your clinical trial is in phase 1 right now, which means it is just looking at the safety of it, right?
Dr. Platt: We are indeed looking at the safety of this treatment; however, we can also say based on what we know about treatments such as surgery and radiation that we are looking at what we would call efficacy, i.e., how well it is going to work. We have a ballpark figure of 5 months or so for surgery and 8 or 9 months for surgery with radiation; so if we can do better than that, which we believe the drug has a chance to demonstrate, then this drug could be used in people.
Where are you at your clinical trial? Do you have any numbers yet?
Dr. Platt: We have enrolled 5 dogs which we started as a basic study to see how well the drug compared to surgery and radiation for instance. We have 2 dogs of those 5 that are still alive 17 and 18 months later, which is very rare.
Can you tell us about Petey?
Dr. Platt: Petey was the first dog that went through this trial in which we did the surgery and then delivered the drug. There is one thing extra I think you should probably know about the trial and that is that most drugs that attack tumors are classed as chemotherapy, but the problem with chemotherapy for brain tumors is most of them cannot get past the barrier that the brain uses to protect itself. We are using a new way to deliver drugs to the brain called convection enhanced delivery where essentially there is a small tube going into where the brain tumor was taken out with the surgery and a pump delivers that drug over about 3 days. In previous work we have shown that the drug will stay there for at least a month while the tumor is attempting to grow back whereas if we actually injected it, it would last a matter of hours and would not get into the brain. So, there are two factors in this trial: one is evaluating this drug for brain tumors and two is a new delivery technique, which will actually get right into the tumor and keep the drug there for a prolonged period of time.
Is that the same case for people too? Your brain blocks the chemo?
Dr. Platt: Yes, absolutely. That is why there is not a lot of chemotherapy out there that is in any way effective for brain tumors.
How big was the tumor for Petey?
Dr. Platt: The tumor was nearly 25% of his brain so we were not really sure whether Petey was an appropriate candidate for the trial; it was such a large tumor that we had to believe that potentially the best of drugs and best of surgery would not get his quality of life back, but there were not many other options for Petey. We knew what we were going to try was at least safe and hopefully not going to make him worse, so the owner in addition to us elected to push this forward and see what happens.
He had surgery then 3 days of this new drug pumped directly into his brain and then how long until you saw a difference?
Dr. Platt: We probably saw him start to regain his personality after about 2 to 4 weeks. For the first few days he was given continuous pain relief after the surgery. There were areas of his brain that were already bruised and damaged which had to be allowed to recover for maybe 2 to 4 weeks before he got his personality back. At that stage we thought that this was great news; we had not harmed him in anyway, he was doing a lot better, and so we looked at gaining 5 to 6 months of good quality of life for Petey with the hope that the drug would add a bit more. Petey is still alive 22 months later and according to the owner and from what we can see, looks better than before surgery. In fact, the owner says he cannot see any abnormalities, with no further seizures, and with Petey now being very interactive with the family. For us to hear that, which we have never seen with any other treatment, gives us a great deal of hope for this.
Are you even surprised by this?
Dr. Platt: We are astounded by it. We wanted to believe in the drug and to believe in the trial, but we had no idea that we would see this level of success. We do not want at this stage to believe that we have found a ‘wonder drug’. It is probably not going to do the same for every dog with the same disease, but we have got another dog who is 20 months out after the treatment with the same disease; so 2 out of 5 that have lived that length of time is great news for us.
Did you ever imagine when you got into this that you would be testing out a drug that could help people?
Dr. Platt: No. I think we have looked over the last few years for any opportunity to improve treatment for dogs and unfortunately, a lot of that treatment is expensive. It is difficult to use new treatment in dogs when we are not sure about the safety of it but here we were presented with something that we knew was going to be safe and so we thought that was great. We hoped that we could help dogs out but to believe that then we would go that next step and potentially help people out is extraordinary.
What about this drug? Is it very expensive too?
Dr. Platt: I do not know how expensive it is.
Is there anything else you would like to add?
Dr. Platt: Probably the only other thing is where we are going from here. We enrolled 5 dogs in this trial to see whether we would be able to prove some effect of this drug, and if we could, then we could apply for funding to do more dogs and get more data to make it more believable. We got funding from the American Kennel Club K9 Health Foundation to treat another 15 dogs in the same manner and so we have started enrolling those dogs in the trial looking to see if we can get results as good as we have seen with Petey.
END OF INTERVIEW
This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.
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If you would like more information, please contact:
Simon Platt BVM&S MRCVS
Dipl. ACVIM (Neurology) Dipl. ECVN
Professor Neurology & Neurosurgery Service
Department of Small Animal Medicine & Surgery
College of Veterinary Medicine
University of Georgia
(706) 542 3221
To read the full report, Killing Canine Brain Tumors , click here.