Randomized controlled experiments have found that vitamin C

Randomized,

controlled experiments have found that vitamin C is not effective in treating terminal cancer

patients.22 However,a 1976 research paper reported that terminal cancer patients given vitamin C survived much longer than did historical controls. The patients treated with vitamin C were selected by surgeons from a group of cancer patients in a hospital.23 Explain how this experi- ment was biased in favor of vitamin C.???

Solution

Because the groups were not randomized, surgeons may have tended to give vitamin C to healthier patients and not to patients for which they thought no treatment could be effective.

The study was not a clinical trial in which patients were compared to carefully matched patients chosen at random and followed using a standardized protocol. Instead, it was attempted to reconstruct what happened to the control group by examining their medical records. Most cancer specialists and journal editors are extremely reluctant to accept this type of study for evaluating the validity of contemporary cancer therapy, primarily because bias may occur in selecting controls.

It may be possible that the patients began getting vitamin C when they were judged \"untreatable\" and their subsequent survival was compared to that of the control patients from the time they had been labeled \"untreatable.\"

Another reason if the two groups were comparable, the average time from the initial diagnosis to \"untreatable\" status should be similar for both groups. But they were not. So, it can be concluded that many of patients had been labeled untreatable earlier in the course of their disease and would therefore be expected to live longer.