Saturday, August 19, 2006

Clinical Trials: Phase 1, 2 , 3 and 4 ---(3)


These trials compare new treatments with the best currently available treatment (the standard treatment). They may compare

* A completely new treatment with the standard treatment
* Different doses or ways of giving a standard treatment
* A new schedule of treatment with the standard one

Phase 3 trials are usually much larger than phase 1 or 2. This is because differences in success rates may be small. So, you would need many patients in the trial to show the difference.

For example, 6% more people get a remission with a new treatment compared to standard treatment. If a phase 3 trial gave the new treatment to 50 people and the standard treatment to 50, on average, there may be 3 more remissions in the new treatment group. The 2 groups would not look that different. If they gave each treatment to 5,000 people, there could be 300 more remissions in the new treatment group.

Sometimes phase 3 trials involve thousands of patients in many different hospitals and even different countries.


Phase 3 trials are usually randomised. This means the researchers put the people taking part into 2 groups at random. One group gets the new treatment and the other the standard treatment. There is more about randomisation and different types of trials in this section.


Trial overviews are studies that combine all the results from phase 3 trials of a new treatment. They are sometimes called meta-analyses. The idea is to get a broader picture of how well a treatment works. The more data (information) you have, the more accurate the results are likely to be.

Source: Cancer Research UK

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