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).
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.
