Patients are seen regularly to determine the effect of the treatment, and treatment is always stopped if side effects become too severe. The purpose of a phase I study is to find the best way to give a new treatment and how much of it can be given safely. In a phase I study, a new treatment is given to a small number of patients. For a new drug, the study starts by giving a very low dose of the drug, then the dose is slowly increased as new patients enter the trial. The dose can be increased by giving more at one time or by giving the same dose more often.
Physicians watch patients carefully for any harmful side effects.
Although the research treatment has been well tested in laboratory and animal studies, the side effects in patients can not be completely known ahead of time. I studies may involve significant risks for this reason. They are offered only to patients whose cancer cannot be helped by other known treatments. Phase I treatments may or may not produce anticancer effects, but some patients have been helped by these treatments. Once the best dose is chosen, the drug is studied for its ability to shrink tumors in phase II trials.