Metronomic chemotherapy is the continuous administration of low doses of chemotherapy to your pet. This could be daily or every other day, but essentially ensures your pet is getting the treatment it needs with little to no rest periods.

Following recent developments, the treatment works by controlling the tumour and depriving it of its blood supply, rather than killing the cancerous cells and attempting to directly cure your pet from cancer, like with usual chemotherapy treatments.


We will give you all the knowledge you need to make an informed decision about metronomic chemotherapy, including the advantages, key considerations and metronomic chemotherapy side effects.

What is metronomic chemotherapy?

As we have already touched on, metronomic chemotherapy is more focused on reducing or eliminating the blood supply to your pet’s cancerous tumour. Treatment in this way also prevents new blood vessels to the tumour forming, as well as allowing the immune system to develop a response against the tumour.

After recent developments in oncology, this new approach has been developed so the tumour can be controlled and kept in the body (as long as it isn’t causing any other problems) but your pet isn’t suffering as the tumour grows.

… and so far, this approach has been very successful.

How is metronomic chemotherapy administered to dogs and other pets?

The key to success is the administration of repetitive, low doses of the drug, usually between 5% and 25% of the ‘standard’ dose in order to reduce toxicity.

When it comes to your pets, these chemotherapy drugs need to be re-formulated into smaller capsules, particularly if your pet is a smaller breed, and may be ordered specifically for them.

When should you consider metronomic chemotherapy for your pet?

Often, metronomic chemotherapy isn’t considered the standard when treating cancer, both in humans and pets, but can be helpful if you want to explore other options or potentially as a trial.

It is most commonly considered when dogs and cats in particular have metastasis (or spreading of the cancer), when soft-tissue surgery isn’t possible, when alternative treatments have failed, or if the owner wants to look into less toxic options, which also happens to be a little less expensive.

If your pet is suffering from any of the following, it may be an indication they they are a good candidate for metronomic chemotherapy:

  • Low-grade soft tissues sarcomas that have been partially removed
  • Splenic hemangiosarcoma
  • Metastatic pulmonary carcinoma
  • Transitional cell carcinoma of the bladder
  • Indolent lymphoma
  • Chronic lymphocytic leukaemia

It is also worth bearing in mind that metronomic chemotherapy can be safely added to other cancer treatments, including radiation therapy.

What are the advantages of metronomic chemotherapy?

While standard chemotherapy aims to kill cancerous cells, it can sometimes also kill off some normal cells too as it targets all rapidly growing cells in the body. This is why there is always a rest period of a few days or weeks, which is to allow the normal cells to recover.

With metronomic therapy, however, there is no such rest period as the toxicity of the drug is drastically reduced and the normal cells will be affected on a much lower level.

Other benefits of metronomic chemotherapy are:

  • The drug can be administered orally to your pet at home
  • The cost is relatively low compared to other chemotherapy options
  • The chance of negative metronomic chemotherapy side effects are low

However, it is also worth considering that once you have started metronomic chemotherapy, it is considered a life-long therapy as it keeps your pet in remission.

It can also take a longer time for a response to occur so if your pet is in the later stages of cancer then there may not be enough time for the treatment to become effective.

What are the metronomic chemotherapy side effects?

The side effects of metronomic chemotherapy can be relatively painless compared to that of ‘traditional’ chemotherapy treatments.

It is a treatment that is usually well tolerated with around 90% – 95% of pets experiencing no side effects whatsoever. Saying that, there are a few potential metronomic chemotherapy side effects you may need to be aware of.


Cystitis is essentially the inflammation of the bladder. There are a handful of signs to watch out for, which may tell you that your pet is suffering from cystitis:

  • Your pet is trying to urinate and nothing is passing
  • They seem to be in pain when they are urinating
  • They’re urinating small amounts frequently
  • Their urine is bloody or cloudy

Measures are taken to reduce the risk of development and to notice it as early as possible, but make sure to see your vet if they do seem to be suffering with cystitis as it may be a case that the metronomic chemotherapy treatment needs to be withdrawn.

Vomiting, diarrhoea or loss of appetite

Around 5% of pets may experience vomiting, diarrhoea or a loss of appetite and is usually caused by an anti-inflammatory drug (piroxicam) included in your pets treatment, rather than the primary drug treating your pets cancer (cyclophosphamide).


Melena is the presence of digested blood, rather than fresh blood, in the feces and makes the stools appear black and tarry. It develops when bleeding occurs into the stomach or small intestines and can also be caused by the administration of certain drugs, particularly corticosteroids and non steroidal anti inflammatory drugs (NSAIDs).

While these side effects may be noticed on rare occasions, they usually stop by themselves or are resolved after reducing the dose of the drug or the addition of supportive medications.

How can you care for your pet before and after metronomic chemotherapy?

As we all know, there is no prevention for cancer, but there are a few things you can do to make sure you are reducing the chances of them developing it.

This includes:

  • Having your pet spayed or neutered
  • Minimising sun exposure
  • Ensuring they get regular exercise and maintain a healthy diet
  • Limiting smoking around your pet
  • Keeping your pet away from toxins around the house

During metronomic chemotherapy, however, you may want to keep an extra eye on your pet by:

  • Ensuring they aren’t getting too stressed while having regular check ups
  • Making sure they’re as comfortable as possible, giving them lots of TLC
  • Taking the time to ensure they are getting the required drug doses of treatment at home 
  • Looking out for any abnormal habits or changes to their appetite 

These are all great ways you can make sure the treatment and your pet is going to continue on with a normal, healthy life. For more advice, read our article on caring for a pet with a chronic illness.


If you are worried your pet may have cancer then speak to your vet as a matter of urgency. Or if you are considering metronomic chemotherapy, they will be able to help you with treatment recommendations too.

If you need some further advice around metronomic chemotherapy side effects, or metronomic chemotherapy in general, then please don’t hesitate to contact us.