Interview with Pilar Xifra Rubio- Part 1
IODOCAT is the first veterinary practice in Spain that has ever offered radioiodine treatment for cats with hyperthyroidism. Pilar Xifra is in charge of this innovative project. In this first part of the interview, Pilar speaks about how the idea occurred to her and how she put it into practice. She also talks about her collaboration with Mark Peterson in the book Feline Endocrinology (2019 Edward C. Feldman, Federico Fracassi, Mark E. Peterson, Ed Edra S.p.A.) and about different ways to use scintigraphy in veterinary medicine.
- Hi Pilar! Thank you for finding time for this interview. I know you are a busy vet. You have set up the first practice in Spain that offers radioiodine treatment for hyperthyroid in cats. You also appear as co-author in Feline Endocrinology. These are really admirable achievements. Congratulations! Tell us please how did this all happen?!
- Thank you. It is a pleasure for me to be here. I am now a new fan of lagateramedicinafelina.blogspot and your podcasts. Regarding my contribution to the book, I am over the moon. This was way beyond my expectations. When I received Peterson’s email offering me to contribute to the chapter about treatment of hyperthyroidism, I just could not believe it. I had to read the email a few times! I would have never thought I would be part of such an exciting project.
Regarding IODOCAT it all started at the GEMFE (Spanish Association of Feline Medicine) Congress in Spain. We were fortunate to have Peterson here delivering lectures about feline hyperthyroidism. As you know, I am a member of GEMFE. I am very interested in feline medicine. I could not understand why we had no radioiodine in Spain. I almost did not know what they were talking about. It all sounded a bit like Chinese to me. I thought it most likely was very complicated and that was why we did not have any radioiodine available. Hyperthyroid cats had to go to Paris if the owners wanted them to be treated. I had a cat with hyperthyroidism that had adverse effects from methimazole. He developed pancreatitis amongst other clinical signs and that was not even a curative treatment. How good is it to be able to cure a disease! And radioiodine allows you to do that.
A few months after the congress, on a night out, I met a couple of pharmacologist who work at a big hospital here Madrid (Puerta de Hierro). I think that was one of the most productive Gin Tonics I have ever had. One of them is very interested in the veetrinry medicine field. He would have liked to be a vet. We started talking about the lack of radioiodine treatment in Spain and they put me in touch with a nuclear physicist in charge of the nuclear medicine department in Puerta de Hierro.
Compared to what they do in human medicine he found that helping me would be fairly easy. I started to regularly go to the hospital to learn about nuclear medicine. I learnt about scintigraphy and radioiodine. At some point I sent an email to the doctor or Mark Peterson. I assumed he was not going to reply. At the end of the day… I am nobody! However he is a very kind man… and he replied! I was so excited about his email. I also had to read it a couple of times before believing it. After having a chat with my husband we concluded that I had to go to New York. I wanted to learn about this somewhere where I could see its application to veterinary rather than human medicine. Mark Peterson and his team are all very kind people and I felt really welcome.
It was during that trip when I made the big decision. I went in March and it was snowing a lot. Oh my god: for somebody from Spain it is difficult to cope with such a cold weather when it was meant to be spring! I was not impressed. Anyway, when I asked Peterson for his opinion about my project he just said: “Done”. So I came back to Spain and started contacting people I needed help from. That was in 2016. It took me two years to set it all up.
- Well I think that is not such a long time, taking into account the magnitude of the project…
- I guess… But to me it was definitely long! It was also fun. When I started talking to the nuclear physicist I thought he was going to think I was crazy: “Really? Treating cats with nuclear medicine?” I thought that they would laugh at me.
- How difficult was to process the bureaucratic side?
- First I needed a nuclear physicist to help me getting a license. You also need different devices. We use the gamma camera to take a visual image of the thyroid tissue. We also have a Geiger counter to monitor the radiation levels for health and safety purposes. This counter also helps to work out the dose that we need in every individual case. The person in charge of the premises needs a special qualification so I had to study quite hard. I found it interesting but also challenging. There are a lot of technical terms and physics involved.
- That sounds challenging indeed. Do you use scintigraphy for something else besides the treatment of hyperthyroidism in cats?
- Initially I only considered its use in feline hyperthyroidism. However, when I went to the Puerta de Hierro, I started looking at other possibilities. Actually I have written a paper about the use of scintigraphy in other pathologies. It will be available next month in AVEPA’s journal.
- That is so good! I look forward to reading it!
- It is a diagnostic method that offers plenty of advantages compared to other diagnostic tests. It gives you information about the function of the organ, besides about its anatomical location. An ultrasound or a CT or an MRI will not offer you that. Another advantage of this diagnostic test is that the exposure to radiation is much smaller than the exposure involved in a CT scan or an MRI. CT radiation is 200 times stronger than scintigraphy’s. Scintigraphy allows you to be with the patient, we do not need distance in between.
So what is a scintigraphy? This method involves injecting the patient with a substance containing atoms that emits gamma particles. That allows the gamma camera to catch an image from the patient's radiation. Besides the radioactive component, this substance that we inject has also a carrier which “takes” that radioactive component to the tissues you want to send it to. If you want to see bones you use phosphate as carrier. That allows you to see where the bone destruction is. We have done this to diagnose lameness in dogs. Scintigraphy is much more sensitive to detect this type of lesions than radiography or MRI. It also detects metastasis in bone tumours at an earlier stage than CT or MRI. We also use it to detect hypothyroidism in cats and dogs. It is helpful to identify thyroid carcinoma causing hypothyroidism in dogs with an unidentified mass on the ventral cervical region. It helps to identify tissue infiltration and metastasis.
Renal scintigraphy is however my favourite one (after thyroid scintigraphy of course). It is a dynamic scintigraphy, so you see how the radioactive susbtance is flowing through the kidneys. It allows you to measure the glomerular filtration rate, what is very helpful before nephrectomy to assess the function of the remaining kidney. And it detects kidney injury much earlier than creatinine and SDMA.
- What's the toxicity associated with this diagnostic method?
- There are no toxic effects.
- Well… it is scary to talk about injecting nuclear stuff in cats with renal disease...
- The radioactive isotope has no harmful effects at all. It is really useful: it has exclusively glomerular filtration and no tubular filtration. In human medicine there are no boundaries diagnostic tests. They frequently use scintigraphy and also PET- CT, which is also nuclear medicine. For instance, by marking neutrophils and injecting them back into the patient we can find the specific location of a hiding infections, sites of inflammation or gastrointestinal ulceration and haemorrhage.
Wow it sounds like science fiction!
- We also use it to detect portosystemic shunt (PSS). It is a very simple test where the pertechnetate is administered as a colonic enema. In a normal cat it would go first to the liver and then to the heart. If it he goes straight to the heart without going to the liver first, there is a PSS. It allows you to distinguish an extra hepatic from an intra-hepatic shunt. However it is not as sensitive as a CT scan at locating the intra hepatic shunt. I still find it very useful in situations where the practitioner is not sure about the presence of PSS or in cases with new colateral PSS. It is less invasive than other advanced imaging tests, it does not require general anaesthesia and the amount of radiation exposure is also reduced. If the cats is cooperative and stays still for a few minutes whilst you inject the drug, it does not need sedation.
Bone scintigraphies are the most time-consuming once because the patients are usually big dogs. It may take a few hours to get it done.
- And what type of substance do you use in these cases?
- The main substance used in scintigraphy is technetium, usually combined with something else. In bone scintigraphy we use Technetium HDP, whereas in renal scintigraphy we use Technetium DTPA. They need acronyms because they all have different and very complicated and long names! In liver scintigraphy we use pertechnetate, the same as in thyroid scintigraphy. The half-life of a radioactive isotope is the time it takes for its effect to drop to 50% of its initial value. Technetium has a half-life of only 6 hours and generates a much smaller radiation than I131, which has a half-life of 8 days. That is why the patient remains radioactive for a longer time. In human medicine the most used iodine is I123, which has an even shorter half-life and does not destroy thyroid tissue. The aim is to minimise the side effects. I131 would allow us to locate the abnormal thyroid tissue, but we would be treating it at the same time and that would generate a greater amount of radiation that we can avoid by using pertechnetate instead…
The second part of this interview will be available in a few days….