False Positive by Theodore Dalrymple

Author:Theodore Dalrymple [Dalrymple, Theodore]
Language: eng
Format: epub
ISBN: 9781641770477
Published: 2019-12-14T16:00:00+00:00

Another problem facing doctors is that patients like certainty. On the few occasions when I have been seriously ill and nigh unto death, I wanted my doctor to know exactly what to do, and to know it on a rational basis. Patientkind cannot bear very much uncertainty. Unfortunately, life and science are often not as unequivocal as we should like. Two papers in this week’s Journal illustrate this truth.

The first concerns adjuvant therapy in certain cases of cancer of the breast. In this trial, 2,400 patients were assigned to receive the drug pertuzumab (actually a monoclonal antibody) in addition to standard therapy, while 2,405 patients were assigned to receive standard therapy and placebo. The conclusion was that pertuzumab “significantly improved the rates of invasive-disease-free survival among patients with [a certain kind of] early breast cancer.” It may be noted that the trial was sponsored by the manufacturer of the drug, but a commercial interest does not automatically lead to intellectual corruption.

There was no statistically significant difference in the death rates of the two groups at 48 months of follow-up. Thus the drug did not appear to prolong life (though it might be found to have done so on longer follow-up). But results were better when it came to invasive-disease-free survival, which might lead to a better prognosis later. Of those treated with the drug in the most at-risk group of patients (i.e. most likely to have a recurrence), 89.9 percent were free of invasive disease, as against 86.7 percent of those treated with placebo. This result was unlikely to have arisen by chance. One of every 112 people treated with the drug, or one of 56 in the high-risk group, will be spared from invasive disease that would otherwise appear at three years.

The principal side effect of the drug was diarrhea, said to be mainly mild, and lasting only during the treatment itself, for up to a year.2 It occurred in 9.8 percent of those treated with the drug and 3.7 percent of those who received placebo. Does the benefit of the drug outweigh its disadvantage? Yes, almost certainly. But pertuzumab is probably very expensive (though no price is indicated). Is it worth the cost? That depends on who is paying, and how much. A nasty question.

The other paper that illustrates medical uncertainty concerns the follow-up of patients with early prostate cancer treated either with prostatectomy or by observation (watching and waiting). In general, prostatectomy gave slightly better results as far as mortality was concerned, but the difference was just below statistical significance, which means that there was a slightly greater than 5 percent chance that the results arose by chance. This does not mean, however, that they did arise by chance; the superiority of surgery might have been genuine, though not very great. On the other hand, those who underwent surgery experienced more side effects that interfered with their quality of life at two years’ follow-up and that persisted at ten years.

The doctor has to advise the patient and the patient has to decide.

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