Which drugs to use, alone or in combination, is decided on the basis of many factors, including the extensive guidelines for treatment in the cancer literature. Yet each treatment program is, in a sense, an experiment, since the results in a particular patient cannot be predicted. There are no guarantees. It is not possible to state
ahead of time whether a certain drug or combination of drugs will stop or slow down tumor growth in
a certain individual.
Doctors are able to estimate, for example, that perhaps 30 or 55 or 73 percent of patients can be expected to respond to a particular drug program for a particular tumor. But they cannot know until they conduct the treatment trial whether any one individual will respond with the hoped-for tumor shrinkage.
What "Response Rate" Means A misconception often arises when a doctor says that a drug has, say, a 60 percent response rate. Patients sometimes think this means that the drug will be at least partly effective against tumors in all treated patients. But to say a drug has that response rate is like saying that a diaphragm or condom is a 95 percent effective way of preventing conception. That figure doesn't mean that all women will become 5 percent pregnant. It means that those contraceptives work 100 percent of the time in 95 percent of the people who use them and don't work at all for the other 5 percent.
Similarly, a drug with an average response rate of 60 percent means that 60 percent of the patients receiving it will respond. But 40 percent will not, although tumor growth might be delayed in some of them.
