FAQ - Prognosis or Outcome

What is prognosis?

Prognosis is a term used to predict how long your pet may be free of disease or may survive. It is the likelihood or chance of recovery from a disease, based on the available evidence. Certain factors can affect the prognosis and treatment options, including age, general health, presence of concurrent conditions, whether this is the first diagnosis or recurrence, etc.

Very few prospective studies have been published about pets with cancer. Therefore, most of the information available on how well animals do after being diagnosed with cancer comes from studies that follow a series of cases.

Prognosis is usually expressed as a probability of survival sometime after diagnosis, such as a one-year survival rate being the probability of surviving for 1year from the time of diagnosis. Alternatively, prognosis can be expressed as the period of time that has passed until 50% of the patients are still alive, and this is the median survival time (MST).

Survival times are averages for that condition and don’t take into account your pets precise situation. For example, a 12 month average or median survival time may be made up of a group of animals that survive from 4 months to 18 months or from 8 months to 24 months.

While it is often hard to predict the future for your pet, your vet will try and take all factors into account when suggesting likely survival times.

What is remission?

Complete remission (CR) is defined as when the tumour can longer be detected. This can be based on physical size of the tumour or by imaging with radiography or ultrasound. Unfortunately, complete remission is not the same as a cure.

Generally, the smallest mass that can be detected by radiographs is about 0.5 cm, more sophisticated imaging can detect down to 0.25cm but this still represents approximately a million cells.

Partial remission (PR) is defined as a reduction in size by more than 50%. Static or stable disease (SD) is defined as change in size (smaller or larger) of less than 25% and progressive disease (PD) is defined as increase in size of more than 25%.

Using these definitions helps your vet to define the effectiveness of treatment or the next course of action.