The Formulated Prognosis

Before answering the question of how long a patient has to live, physicians must first formulate a prognosis, or determine in their own mind how long they think the patient will live.

Within the palliative care literature, there are several studies specifically designed to determine the quality of physicians’ formulated prognoses in patients with advanced illness. These studies report quality in the form of physicians’ prognostic accuracy in predicting survival of patients following admission to hospice programs (Parkes 1972, Evans 1985, Heyse-Moore 1987, Forster 1988, Maltoni 1994, Christakis 2000). Investigators in these studies have measured physicians’ prognostic accuracy by comparing patients’ observed survival to their predicted survival (these predictions are not necessarily ones communicated to patients; rather, they are ones physicians formulate for themselves).

Results of the studies, summarized in Table 1, show that, in aggregate, physicians’ overall survival estimates tended to be incorrect by a factor of approximately three, always in the optimistic direction (Parkes 1972,Evans 1985, Heyse-Moore 1987, Forster 1988, Maltoni 1994, Christakis 2000).

 

Summary of Studies Comparing Physicians’ Estimated Survival to Patients’ Actual Survival

Primary investigator

Reference

Year

Number of Doctors

Number of Patients

Median estimated survival (wk)

Median actual survival (wk)

Estimated survival/actual survival

Parkes
2
1972
NR
168
4.5a 2.5a 1.8
Evans
3
1985
3
42
NR NR 3.2c
Heyse-Moore
4
1987
NR
50
8 2 4
Forster
5
1988
3
108
7b 3.5 2
Maltoni
6
1994
4
100
6 5 1.2
Christakis
7
2000
343
468
NR 3.4 5.3 c
NR, not reported.
a Values estimated from graph in paper.
bSeven weeks calculated through statement in paper that survival was overestimated by 3.4 weeks on average.
c Ration of mean estimated survival/mean survival.

 

Studies of physicians’ abilities to predict terminally ill patients’ survival are not limited to patients in palliative care settings, but have also been evaluated in ambulatory patients undergoing anticancer therapy. Investigators measured oncologists’ prognostic accuracy in the care of their ambulatory cancer patients by asking them to first predict patients’ likelihood of cure and then to estimate the duration of survival for those whose likelihood of cure was zero (Janisch 1994).

At the 5-year point, patients who were alive and disease-free were termed “cured” the dates of death of the incurable patients also were determined. The researchers reported that oncologists were highly accurate in predicting cure. That is, for subgroups of patients (not individual patients) the ratio of the observed cure rate at 5 years to the predicted cure rate was quite high, at 0.92.

However, the same oncologists had difficulty predicting the length of survival of individual incurable patients. They predicted survival “correctly” for only one-third of patients, with the errors divided almost equally between optimistic and pessimistic.

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