Chemotherapy for Cats

Feebee cat in blue chair

While cancer in cats is not as common as it in dogs, it is still one of the leading causes of death in older cats. According to the Animal Cancer Foundation, 6 million cats will be diagnosed with cancer in the United States along. And because cats are masters at masking illness, it is often harder to detect.

Cancer used to be a death sentence for cats, but recent advances in feline cancer research have made treatment possible in many cases. Just like with human cancers, early detection is key to successful treatment.

Treatment options for cats are almost as varied as treatment options for human cancers, and will depend on the type of cancer. Surgery is the most common treatment for any lumps or growths that need to be removed. In some cases, surgery can be curative. Other cancers may require chemotherapy or radiation.

How chemotherapy works

Chemotherapy uses drugs with the objective to kill cancer cells with the least possible amount of damage to normal, healthy cells. In human medicine, the goal of chemotherapy is to achieve a cure. In cats, chemotherapy is aimed at controlling the disease and achieving a period of remission for the cat. Chemotherapy is typically used for cancers that affect multiple sites. Lymphoma is the most common form of feline cancer that is treated with chemotherapy. The drugs used in veterinary chemotherapy are frequently the same drugs used in human medicine.

Most cats tolerate chemotherapy well

Most cats tolerate chemotherapy well. Some cats may experience side effects such as vomiting, diarrhea or poor appetite, but these side effects are usually mild and can be managed with supportive care. Only a very small number of cats on chemotherapy will require hospitalization due to the side effects of chemotherapy. Unlike humans, cats will not lose all their hair. Most cats will lose their whiskers, and shaved hair will be slow to grow back, but substantial hair loss is uncommon.

Support your cat’s immune system

It is important to support your cat’s immune system while she is undergoing chemotherapy. One of the foundations of a healthy immune system is diet. Typically, veterinarians recommend a high protein, low carb, moderate fat diet for pets with cancer. A high quality grain-free canned diet will probably be your best choice for your feline cancer patient.

Even though I’m a proponent of raw feeding, I’m on the fence as to whether raw diets are appropriate for cats with cancer. On the one hand, there are numerous anecdotal reports of miracle cures when pets with cancer were fed a raw diet, on the other hand, I don’t know whether feeding a raw diet to an immunocompromised pet is necessarily a good idea. Check with a veterinarian who is familiar with raw feeding whether a raw diet is appropriate for your cat while she is undergoing chemotherapy.

Supplements and herbs

Supplements and herbs can provide immune system support during treatment. Probiotics not only help maintain a healthy gut flora, but also boost the immune system. Anti-oxidants and increased amounts of omega-3-fatty acids may also be indicated. Check with your veterinarian to determine which supplements are indicated for your cat.

Supportive therapies such as acupuncture, Reiki or other forms of energy healing can support your cat through her treatment. These therapies will not interfere with conventional medical treatment.

How will you know whether chemotherapy was successful?

A cat in remission doesn’t look any different from a cancer-free cat. Typically, a successful remission means that lymphnodes will go down to normal size, and if there were any signs of illness that were related to the cancer, they will disappear. Remission can last anywhere from weeks to months, and for some lucky cats, even several years.

My personal experience with feline cancer

My first cat, Feebee, was diagnosed with intestinal lymphoma when he was 15 years old. He tolerated his chemotherapy protocol of a combination of Vincristine injections and oral Cytoxan and prednisone well. He would be a little subdued for about 24 hours following treatment. His appetite wasn’t that great during that period, and he slept a lot more than usual, but the rest of the time, his quality of life was good.

After seven months, he stopped responding to the chemotherapy. My vet gave me the option of continuing with more aggressive drugs with the potential for more severe side effects. I elected euthanasia. My little man confirmed that I made the right decision: he died in my arms while my vet was on the way to my house.

Being faced with a cancer diagnosis is a devastating blow for cat parents. Making a decision about treatment is as individual as the affected cat and her human. There are no hard and fast rules. The ultimate goal of any decision is to provide good quality of life for the cat for as long as possible.

Have any of your cats undergone chemotherapy? What was your experience?

Photo ©Ingrid King

Dr. Goodpet


387 Comments on Chemotherapy for Cats

  1. Zoe
    April 13, 2015 at 5:24 am (1 week ago)

    My 15 year old cat Dillon was diagnosed with large cell lymphoma in January and has since undergone surgery to try to remove the tumour (found to be not possible) and then chemo for five weeks. The chemo protocol was weekly doses of vincristine and cyclophosomide at the vets plus 7.5mg daily of prednisolone as well as mirtazapine to stimulate his appetite and cerenia to combat sickness. After 5 weeks the vet said that she thought the tumour had actually grown (she estimated this by touch not by xray or CT), that was almost two weeks ago. Dillon is continually losing weight as his appetite is now so small, we try every type of food and cook fish and chicken for him to try to find something he will take a few mouthfuls of. In the last couple of days he has started to suffer from diahorrea as well but is still alert and mobile. We now don’t know where to go with him. We are due back at the vets this week as he would be due his next chemo next week and she wants to examine him before then. I am so worried that she is going to say that his tumour has grown again and that there is nothing she can do for him. Has anyone experienced a chemo protocol that didn’t work and then found another combination of drugs was successful? I don’t know if I’m grasping at straws here and should let him go instead of putting him through more treatment but I really want to make sure we have done everything possible for him and given him a fighting chance

    • lu
      April 20, 2015 at 6:46 pm (20 hours ago)

      Hi Zoe, I’m so sorry that the current protocol doesn’t seem to be working. Before anything else, I think your vet should confirm their suspicions with an ultrasound or X-ray, at least. If your kitty is brave, not in terrible pain, and seems not ready to go just yet (ie, still interested in his favorite things), I would say try another protocol, if possible. My little dude’s situation is also inoperable, so we’re trying lomustine every 3-4 weeks, along with a daily dose of 0.3ml of 15mg/ml prednisolone. For him, this course may be our only shot, mostly because other treatments require too frequent of extremely stressful vet visits – he wouldn’t stand for it for very long! Ultimately, I think each would prefer to decide what happens to him or her. Best of luck to you guys. ❤️

      • Zoe
        April 21, 2015 at 7:16 am (7 hours ago)

        Hi Lu, thank you for your response. Unfortunately Dillon passed away last Wednesday. He died peacefully in my husband’s arms so whilst we are devastated and miss him terribly he passed away in the best possible circumstances. Good luck with your little guy, I hope he manages to keep fighting

        • Lu
          April 21, 2015 at 1:52 pm (40 mins ago)

          I’m so sorry for your loss. :( God bless you guys.

        • Ingrid
          April 21, 2015 at 2:05 pm (27 mins ago)

          I’m so sorry, Zoe.

  2. johnny
    March 7, 2015 at 2:01 pm (2 months ago)

    Sooner has been on Leukran and prednisolone since August 2013
    for his small cell GI lymphoma. He recently had a checkup at Kansas State
    Vet Hospital. Since Sooner is showing increased thickness in various
    sections of his small intestine and he continues to lose weight. He weighs
    about 7 lbs. now. In August 2013 he weighed a little over 8 lbs. The
    oncologist would like to switch him to lomustine every 3 weeks and
    denamarin.We are not sure if this is a good move. Also, the other options is cyclophosphamide every 2 weeks. I would like to know what you think about this approach and if anyone else has had this medicine. Thanks, Johnny

  3. Laura
    March 4, 2015 at 7:15 pm (2 months ago)

    Kathy, my heart goes out to you. Please read Rainbow Bridge. I find it emotional but comforting.

    • Kathy
      March 6, 2015 at 4:00 pm (2 months ago)

      Thank you, Laura!

  4. Kathy
    March 4, 2015 at 3:51 pm (2 months ago)

    Following up on my prior posts about Maddie. He finished his first 4-week course on chemo but did not achieve remission. The oncologist gave him Lomustine (sp?) this week, but I am coming to terms with euthanizing him in the next day or two. He is putting all of the time, which I know can be a sign of pain, and is not himself. I’m absolutely heartbroken, but coming here and reading all of your stories was very helpful. It’s nice to know that there are others out there facing things like this, even though I wouldn’t wish it on anyone!

    • jenny astbury
      March 4, 2015 at 4:41 pm (2 months ago)

      So sorry that it hasnt worked out for Maddie. Thinking of you .

    • Ingrid
      March 4, 2015 at 5:20 pm (2 months ago)

      I’m so sorry, Kathy.

      • Jeanette
        March 4, 2015 at 5:30 pm (2 months ago)

        Kathy, I’m so sorry about your Maddie. Sadly we had to help our Chai to her tenth life on Feb 21. She had small cell GI lymphoma and survived 18 months before it spread to her eyes and most likely her brain. I feel for you and I understand your heartbreak. It’s the hardest thing we ever have to do for our beloved furkids and they certainly take a piece of our heart and soul with them to the Rainbow Bridge.

        • Ingrid
          March 4, 2015 at 11:13 pm (2 months ago)

          I’m so sorry about Chai, Jeanette.

          • Jeanette
            March 4, 2015 at 11:28 pm (2 months ago)

            Thank you Ingrid – it has been difficult to lose two kitties to cancer in less than a year.

          • Michelle
            March 5, 2015 at 12:05 am (2 months ago)

            My heart breaks for you.

    • Robin
      March 4, 2015 at 7:51 pm (2 months ago)

      It’s just so heartbreaking. :-(

    • Michelle
      March 5, 2015 at 12:03 am (2 months ago)

      Kathy, I’m sorry. You did your best for Maddie and gave treatment a good shot.

    • Tamara
      March 5, 2015 at 5:42 pm (2 months ago)

      Kathy, I am so sorry to hear about Maddie. My heart breaks for you.

  5. Lyn
    February 13, 2015 at 12:01 am (2 months ago)

    My 16 year old Yuki was diagnosed with small cell lymphoma in dec last year. She has been on Leukeran 1 tablet every 3 days and was on 1 and a half prednisolone tabs every day to begin with. However she was desperate for food and asking to be fed all the time. Her predict was cut to 1 tablet/day and she settled down well. Diahorrea cleared up and we had no vomiting. She put on a little weight. At last vet check her pred was decreased to 1 tab every other day. One week later she was vomiting and had diahorrea worse than before she was diagnosed. I took her to a local vet who gave her a cortisone injection as she’d vomited her pred vup the night before. She has lost her appetite and is getting thinner. Diahorrea is just as bad. Don’t know if she’s no longer responding to the leukeran or if the decrease in pred upset the balance we had going. Very disappointing given that she had no visible side effects since commencing her treatment.

    • Ingrid
      February 13, 2015 at 7:14 am (2 months ago)

      It does sounds like Yuki may have come out of remission, Lyn. I’m sorry, I know this is so hard.

      • Lyn
        February 14, 2015 at 11:29 pm (2 months ago)

        Two days later…Yuki is eating again, not vomiting and diahorrea has subsided with intermittent formed stools. Cleaning herself and back into her usual habits. Hope the return to 1 tab/day prednisolone is the reason and that she’s with us for a bit longer.

        • Michelle
          February 15, 2015 at 12:06 am (2 months ago)

          I’m glad to hear that. I was hoping that changing the dose would work.

        • Ingrid
          February 15, 2015 at 7:24 am (2 months ago)

          That’s wonderful news, Lyn!

        • Julie
          March 21, 2015 at 10:41 am (1 month ago)

          Our 16 yr old male cat is doing IV chemo along with 5mg prednisone, weekly, for 2 mos. He will continue the same for 2 mos. He is responding well. He did have a $3,000 bout of pancreatitis thrown in along the way, which was devastating. We have put him on digestive enzymes plus probiotics. We are using NWC Naturals brand, but there are several brands out there. I think that if you can return good bacteria to your cat’s gut, it helps keep him/her better able to combat the assault of chemo. Like doctors for humans, vets aren’t necessarily interested in natural remedies. I asked the oncologist about what I wanted to use, and he said that he saw no problem with it. They don’t tell you that pancreatitis is common in cats undergoing chemo. Surprise! Good luck to all of us.

          • Ingrid
            March 21, 2015 at 11:06 am (1 month ago)

            I agree that probiotic support is a great way to support the immune system during chemo (or at any other time for that matter – I recommend a daily probiotic supplement for all cats.) My go to product is the Dr. Goodpet Feline Digestive Enzymes product. It’s a combination of enzymes and probiotics:

            All my best to your cat as he goes through treatment, Julie!

  6. Tamara
    February 3, 2015 at 11:38 am (3 months ago)

    Thank you for taking the time to respond. I appreciate all of your input. Today he gets a lower body ultrasound and we will take it from there. Has anyone on this forum opted to not do the chemo? and If yes, what was the outcome?

    • Glenda
      February 5, 2015 at 11:50 pm (2 months ago)

      I’d also like to know about those opting out of chemo. My 11 year old boy, Chance, was diagnosed today and I’m not sure I want to put him through chemo just to have him deal with being sick again later :(

      • Robin
        February 6, 2015 at 9:52 am (2 months ago)

        My kitty has had small cell lumphoma for over a year. He got 3 chemo pills every 2 weeks(I put all 3 pills in a gel cap so it was one dose) and didn’t really have to “deal” with much at all other than living a normal, happy, thriving life. The only other meds he got was an anti nausea pill the day of and day after getting the chemo pills as a precaution just in case (he never did vomit) and twice a week he got and still gets a little bit of a laxative mixed into pure chicken baby food. His Oncologist stopped his chemo at the end of Dec and is hoping he’ll stay in remission. If not, he’ll get back on the chemo again and there’s a 95% chance he’ll go back in remission. Considering he’s been a happy cat that you couldn’t tell from one not fighting cancer, it’s been well worth it. Early on, it took about 4-6 weeks to get the right dose, etc, so sometimes it takes a little adjusting by the vet to get the right response.

      • Kaite
        February 8, 2015 at 7:56 pm (2 months ago)

        I would not be afraid of chemo at all. I put my 17 year old cat on chemo about 4 months ago, and he is now thriving. He looks better and is chubbier now than he was 1.5 years ago, which was well before his lymphoma diagnosis. He became slowly and progressively skinnier between the ages of 15 and 17 years, and now he is a lovely plump cat again. He looks like he is 10 years old, and he has had no side effects from chemo. In fact, his vomiting and diarrhoea cleared up immediately. Not putting a cat on chemo will mean that kitty will deteriorate much sooner, whereas a cat has a chance to live a long time, with good quality of life, if he/she has chemo. I never expected to see my boy look so good again, and that’s at the age of 17.5 years. I think the only exception would be if the cat is suffering and has other health issues that impact.

        • Robin
          February 8, 2015 at 8:08 pm (2 months ago)

          Well said, Kaite!

    • Luna
      March 23, 2015 at 2:34 pm (4 weeks ago)

      Our cat had large cell lymphoma and we didn’t put him through chemo.
      His quality of life had decreased and he wasn’t enjouying life. His spleen and liver were enlarged.
      We let him go before he got too miserable. It was the hardest choice of our lives.

      • Ingrid
        March 23, 2015 at 3:15 pm (4 weeks ago)

        I’m so sorry, Luna.

        • Kaite
          March 24, 2015 at 5:05 am (4 weeks ago)

          I would definitely do the same if/when my boy is not experiencing good quality of life. It is the kindest thing. I am sorry for your loss.

  7. Jenny
    February 3, 2015 at 9:09 am (3 months ago)

    My little cat Gridlock is still doing well since being diagnosed with large cell lymphoma in June 2013. Like Tamara, I was turned off by the idea of chemo but my vet explained that animals are given much lesser doses than humans – since it would be unethical to cause them discomfort. Gridlock started off with two weekly and then monthly chemo – we dropped one drug which caused her white blood cell count to drop – and she simply had vincristine and a steroid. We are now down to two monthly chemos with monthly steroid injections and the likelihood that we will stop chemo altogether at the two year mark.

    I would say to Tamara go with it – If it isn’t going to help this will rapidly become apparent.

  8. Tamara
    February 2, 2015 at 8:43 pm (3 months ago)

    Hi everyone,
    My sympathies to all of you who have or are dealing with your cat and cancer. Our sweet 7 year old male Lynx Siamese was diagnosed with hemangioma sarcoma about 3 weeks ago. Our vet did an excellent job of removing the tumor. She also did radiology photos of his upper body and fortunately all is clear. Today we saw the Oncologist for the first time . We bring him back to the Oncologist tomorrow for a ultrasound of his lower body. We are hoping for the best but are very turned off to the idea of Chemo. For those of you that have or are experiencing your cat going through Chemo, what are your thoughts? Has anyone else had a cat with this type of cancer? If your cat has or is undergoing cancer, Do you feel chemo has helped or hurt your cat more? We are very nervous and any help or advice is appreciated.

    • Ingrid
      February 3, 2015 at 6:57 am (3 months ago)

      I think you’ll find lots of support here, Tamara. My own cat, who had intestinal lymphoma, went through chemo and lived for seven months with very good quality of life after diagnosis. This was fifteen years ago, and chemotherapy drugs have come even further since then. All my best to you and your kitty.

    • Robin
      February 3, 2015 at 7:14 am (3 months ago)

      My cat had lymphoma…a different type of cancer…and did very well with chemo. After taking some time to get the dose/ frequency right, he had a complete turnaround and has been in complete remission for about a year. He looks and acts like a normal, thriving kitty. Most animals do not have the side effects you think of when you hear the word chemo. It’s not the same as what you hear about the side effects people usually get from chemo. It’s a lot easier.

  9. Laura
    January 28, 2015 at 4:21 pm (3 months ago)

    I certainly don’t know all the answers, but our vet prescribed Prednisone and Cerenia for our Ling Ling. A specific brand of probiotics seemed to assist with her GI tract, and we administered probiotics daily. We tried the Famotidine but it did not prove useful in her case. All cats are different. Our goal was to make her last four months the best we could. We gave her anything and everything we remotely thought she wanted to eat. There was a period when she was eat only raw hamburger meat. Other days, she loved baby food meat, specifically chicken. Toward the end, we gave her Gatorade to made sure she was hydrated. I know it is very early to even consider such, but I want to share. At the very end, we asked our vet to come to our home which reduced stress for her and us. It was the most humane gift we could give her.

  10. Kathy
    January 28, 2015 at 3:45 pm (3 months ago)

    Thank you for your replies. This is heartbreaking for me and I’m doing the best I can to make him comfortable and happy. He started chemo on Monday and seemed to be eating a little better, but then today he’s very tired and hasn’t eaten anything except a piece of lunch meat. He is also on Sucralfate to coat his stomach ulcers before food/meds, Prednisolone, Famotidine (sp?). This morning he vomited a small amount of liquid so I gave him Cerenia for the nausea. When he didn’t improve over the course of the day, I checked his temperature rectally to see if it was high due to an infection. It came in at 99.0, so I’ll check it again this evening. He’s definitely not himself and has spent the entire day sleeping on a small shelf in our bedroom.

    • Robin
      January 30, 2015 at 10:09 am (3 months ago)

      What type of “lunch meat” did you give him? Most of the processed meats from the deli counter have onion and/or garlic added for flavoring, Cats cannot have onion or garlic. It’s very bad for them.

  11. Laura
    January 26, 2015 at 6:01 pm (3 months ago)

    I am so sorry. I will pray that Roach bounces back and does great. We lost our Ling Ling in July, and we still cry. I believe she was misdiagnosed for a long time, and we took her to numerous vets having every test administered that the vet thought was relevant. Cats have such a presence without trying, and our hearts certainly get “wrapped around.”

  12. Kathy
    January 25, 2015 at 8:40 pm (3 months ago)

    Thank you all for pouring your hearts out on here. We got a diagnosis of large cell lymphoma in our 15 yo male cat, Maddie, just yesterday. We set up a consultation with a veterinary oncologist for tomorrow and are hopeful he is a candidate for chemo, but we’ll see. I adopted him as an 8-week old kitten in college and I am absolutely devastated. I am sorry for all of your losses and struggles.

    • Ingrid
      January 26, 2015 at 7:23 am (3 months ago)

      I’m sorry about Maddie, Kathy. I know it’s devastating to receive a cancer diagnosis. Please keep us posted on how she’s doing.

    • Chari
      January 26, 2015 at 5:46 pm (3 months ago)

      Hi Kathy,
      Please keep us updated as to what they are recommending and what is happening. I also have the same situation but Roach is 14 yrs old. I never thought this would ever happen, and I thought I did everything to make the environment and his food high quality. I am also devastated and everyday I cry at some point. I am going to the doctor today to get the Vitamin B injectable the Vet recommended me to give him once a week. When he was first diagnosed on Dec 8/14 I chose not to administer the injection myself and would take him to the doctor every 2 weeks. But now that his condition is worsening, I am willing to do it.

  13. Michelle
    January 23, 2015 at 6:00 pm (3 months ago)

    Chari, I believe what I know will help, though Kallie’s situation isn’t exactly the same. Prednisolone reduces the inflammation in the intestines and stomach. Traditionally, it’s used with chemo for maximum effect. Kallie’s white blood cells were off after a month of Luekeran, every other day 2 mg, so the vet changed the regimen to 2 mg every third day. That did the trick. Based on that, I am not sure why the vet is completely stopping the chemo. However, I wonder if the vet wants to detox the cat then check his blood in 2 weeks to ensure the white blood cells are normal. I recommend you talk to the vet .

  14. Chari
    January 23, 2015 at 5:34 pm (3 months ago)

    I am not sure what to do. My spouse took Roach in for this first blood test since starting Leukeran 2 mg 3X per week and found his white blood cell count was low. I didn’t speak with the vet but the vet told my spouse to take him off Leukeran for 2 weeks then bring him back. He is taking 10 mg of Prednisolone every day and Remeron x2 a week, and Pepcid AC every day. So what now? I know the Prednisolone does not destroy cancer cells so I don’t know why the doctor wants me to bring him back in 2 weeks. Has anyone had this experience?

  15. Laura
    January 22, 2015 at 10:49 am (3 months ago)

    Thank you. Agree. Not the clay litter I worry about but the silica (glass) from the clumper.

  16. Laura Peck
    January 21, 2015 at 11:18 pm (3 months ago)

    I have always been concerned about the chemicals. I read the book, Cat Daddy, and he stated that clumping litter could cause cancer because it contained silica. This resurrected my concerns. I mix the clumping litter with regular litter, but the dust remains on the cat’s fur. When they bathe, they ingest the dust/chemicals. It is great for clean-up and odor control, but if there is documented evidence that it can or does cause cancer, I will make whatever changes are necessary.

    • Ingrid
      January 22, 2015 at 7:28 am (3 months ago)

      I don’t think there’s any documented evidence that definitively ties clay litter to cancer, but there are certainly concerns about the effect it can have on health. Here’s some more information on how you can limit exposure to toxins for your cats:


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  1. […] Cancer used to be a death sentence for cats, but recent advances in feline cancer research have made treatment possible in many cases. Just like with human cancers, early detection is key to successful treatment. Depending on the type of cancer, treatment options may include sugery, radiation, and chemotherapy. […]

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