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SUCCESS RATES IN CANCER TREATMENT
First, how do we define success in the treatment/management of a cancer patient?
There are specific technical measures of success called remission rates. Complete remission is the destruction of all detectable tumour and partial remission is the reduction of detectable tumour by 50%. Static disease is when the tumour has been stopped from growing. Disease-free interval is the time from complete remission to regrowth of the tumour and cure is usually defined (in humans) as complete remission lasting 5 years.
The best kind of remission is that achieved by early surgery, and early surgery provides the best chance of cure in almost all tumours. If the laboratory examination of the tumour suggests that there has been spread from the primary site, adjuvant chemotherapy or radiotherapy given before further evidence of tumour is detected offers the next best chance of log-term success. There are arguments in favour of following this by immunostimulation to maximise the control possibilities.
Where the primary tumour is inoperable, or where a significant secondary spread of tumour can be shown, and there is measurable disease, radiotherapy offers the best chance of long-term management with chemotherapy next in value.
Where disease is advanced, palliative treatment success is not measured by duration so much as by its ability to provide good quality of life for the patient.
A major problem in comparing treatment regimes in pets is the variation in the timing of euthanasia (as compared to the situation in humans where death from disease is not speeded up by the doctors). Survival times are not very good measures for comparison when requirements of individual pets and their owners will vary. Disease free interval is the best measure for comparing treatments in pets.
Approximate success rates for treatment of individual common tumours in pets are: