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249
E D I T O R I A L
Why Is the Prostate Cancer
Death Rate Declining in the
United States?
Curtis J. Mettlin, Ph.D.1
Gerald P. Murphy, M.D.2
1
Roswell Park Cancer Institute, Buffalo, New York.
2
Pacific Northwest Cancer Foundation, Northwest Hospital, Seattle, Washington.
T
Address for reprints: Curtis J. Mettlin, Ph.D.,
Roswell Park Cancer Institute, Elm and Carlton
Streets, Buffalo, NY 14263.
Received August 25, 1997; accepted September
2, 1997.
he National Cancer Institute recently reported data showing that
the prostate cancer death rate in the United States declined between 1990 and 1995. The overall decline was from 26.5 to 17.3 deaths
per 100,000 men in the population.1 Figure 1 shows that the percentage of decline was greatest for younger white men, for whom the
decline was 11.7%, and smallest for older men and African American
men.2 This downward trend represented a sharp break from the prior
pattern of increasing mortality. The overall prostate cancer mortality
rate in the United States had increased 13.2% during the 5-year interval preceding 1990.
There were no published predictions that this would occur, and
no analyses of other data that might explain the reasons for this trend
have been reported. Knowing that to ‘‘look a gift horse in the mouth’’
can tarnish the event, it is tempting not to raise questions about the
meaning of this trend. On the other hand, shifts in patterns of disease
in populations across time are the results of experiments of nature
from which disease control professionals can measure the effectiveness of preceding health care and disease control interventions. Once
learned, the lessons of past experience can guide efforts that extend
and accelerate trends that previously had occurred only fortuitously.
It is possible that the recent declines in prostate cancer mortality
are related to shifts in detection and treatment dating back to the
1970s. If true, this raises important questions about the impact of the
even greater shifts in detection and treatment that occurred after the
widespread introduction of PSA screening in the late 1980s. Skeptical
observers have cautioned that an increase in early detection without
an ensuing decline in mortality should cast doubt on the effectiveness
of early detection as a prostate cancer control strategy.3 Contrariwise,
does the recent favorable trend in mortality now make the case for
proponents of PSA screening? In other words, does declining prostate
cancer mortality argue for increasing efforts to identify men in the
population who have treatable prostate cancer and offer them the
appropriate treatment choices?
Unfortunately, it is easier to speculate about the meaning of prostate cancer death rate trends than to determine their cause. Historical
trends cannot be studied by experimental or even quasi-experimental
q 1998 American Cancer Society
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W: Cancer
250
CANCER January 15, 1998 / Volume 82 / Number 2
FIGURE 1. The decline in age-adjusted prostate cancer mortality rates
is shown for the period 1990–1995. The rate changes are shown as
percentages.
methods, and the death rate trend for any disease is
usually the product of many different factors occurring
simultaneously. Prominent among the variables that
can influence mortality trends are changes in patterns
of disease occurrence, developments in disease specific methods of detection and diagnosis, and shifts
in treatment practice. All of these changes have been
documented in recent years as pertaining to prostate
cancer. In addition to these obvious factors are more
perplexing ones that can give the appearance of significant progress when little has actually occurred.
Such factors as shifts in competing causes of death or
changes in standards of recording cause of death are
examples of artifacts that can confound understanding
of the underlying trends.
Although the number of uncontrolled variables
and the historical nature of the event make it impossible to prove any particular theory of causation, it is
possible to examine the sequence and magnitude of
events that may be used to evaluate what explanations
are plausible and reasonable. For example, prevention
of prostate cancer can fairly readily be ruled out as
an explanation for declining prostate cancer mortality.
Although significant research progress has been made
concerning the environmental and genetic etiology of
prostate cancer, the cause(s) of the disease remain
largely unknown. Unlike lung cancer trends, in which
reductions in cigarette smoking can be correlated to
declines in deaths from the disease, no preventive intervention can be pointed to as a factor in prostate
cancer trends. In fact, the decline in prostate cancer
mortality has occurred in the face of rising incidence
rates.4
It also seems implausible that the observed trends
can be attributed to general change in the accuracy
or procedures for recording the cause of death. First,
the change in direction in mortality does not date back
to some prior era when determination of cause of
death for a man having prostate cancer might have
been ambiguous or death certification standards were
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not highly developed. Prostate cancer mortality was
rising immediately preceding the recent decline, and
modern standards for recording cause of death are
likely to have been applied equally to both intervals.
Secondly, as the data from the National Cancer Institute show, the decline in the death rate is more pronounced for younger men and white men. Any explanation based on the premise that the decline is the
result of an artifact of changes in death certification
would require a subsidiary explanation for this to occur to a greater extent in some age and race groups
than in others. Finally, and possibly most compelling,
is the finding that no specific revision of coding procedures pertaining to prostate cancer as a cause of death
was introduced at the time the death rate began to
change.
Another possibility to consider is that there has
been some breakthrough in treatment that has rendered prostate cancer more curable. There is ample
precedent for this in oncology. Childhood leukemia,
testicular cancer, and Hodgkin’s disease are wellknown examples of diseases for which new treatments
or new combinations of treatments have resulted in
longterm, populationwide declines in the death rates.
Unfortunately, there have been no comparable prostate cancer treatment advances that would similarly
impact on mortality. Although the major treatment
options of radical prostatectomy and radiation therapy
for localized disease are continually being refined, they
have been in use for many years, and there are no
curative treatments for advanced prostate cancer.
Although the basic treatment options may not
have changed much, there is considerable evidence
that the pattern of use of these treatments has
changed. The repeated studies of the American College
of Surgeons document that the proportion of prostate
cancer patients receiving radical prostatectomy or radiation has increased.5 In 1974, 9.2% of all prostate
cancer patients were treated by radical prostatectomy,
and by 1993 this proportion had increased to 29.2%.
The comparable increase for radiation therapy for the
period 1974 – 1993 was from 5.5% to 30.1%. This increased use of potentially curative treatment (as opposed to observation or palliation) happened in concert with a longterm trend toward earlier prostate cancer detection. Between 1973 and 1993, the proportion
of prostate cancer diagnosed at localized stages increased from 56.7% to 74.0%. The public health consequences of increasing treatment rates for prostate cancer may be reflected in the results of a recent analysis
of national SEER data. Those results showed that the
disease specific mortality rate for men treated for prostate cancer (i.e., by surgery or radiation) declined significantly between 1973 and 1990.6
W: Cancer
U.S. Prostate Cancer Death Rate/Mettlin and Murphy
These observations may support the hypothesis
that prostate cancer death rates are declining because
men are increasingly diagnosed when the prostate
cancer is localized and increasingly receive treatments
that reduce the likelihood of death from the disease.
Although not rising to the level of proof, this hypothesis is consistent with a sequence of changes in patterns
of detection and treatment that is well documented in
the literature. Further research is needed to quantify
the association between early detection and declining
mortality. Further research also is needed on competing hypotheses. Finally, continuing close monitoring
of the mortality trend for prostate cancer in the United
States is needed to establish that the downward trend
is not transient and is responsive to continuing
changes in the cancer control interventions applied to
this disease.
As this needed research goes forward, it seems
reasonable to accept the recent decline in prostate
cancer mortality at face value. It is a favorable trend
that probably reflects the impact of increasing emphasis on early detection and appropriate treatment. The
American Cancer Society recently reissued recommendations that men at risk for prostate cancer be
offered prostate specific antigen testing and digital
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251
rectal examination as part of their routine healthcare.7
Based on the recent evidence, this appears to be a
good recommendation for promoting the public’s
health.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
Surveillance, Epidemiology, and End Results (SEER) Program. Age-adjusted U.S. cancer death rates. J Natl Cancer
Inst 1997;89:12.
Office of Cancer Communications. Questions and answers
on trends in cancer mortality [press release, November 15,
1996]. Bethesda, MD: National Cancer Institute.
Kramer BS, Brown ML, Prorok PC, Potosky AL, Gohagan JK.
Prostate cancer screening: what we need to know. Ann Intern Med 1993;119:914–23.
Merrill RM, Potosky AL, Feuer EJ. Changing trends in U.S.
prostate cancer incidence rates. J Natl Cancer Inst
1996;88:1683–5.
Mettlin C, Murphy GP, Menck HR. Changes in patterns of
prostate cancer care in the United States: results of American College of Surgeons Commission on Cancer studies,
1974–1993. Prostate 1997;32:221–6.
Krongrad A, Lai H, Lamm SH, Lai S. Mortality in prostate
cancer. J Urol 1996;156:1084–91.
Von Eschenbach A, Ho R, Murphy GP, Cunningham M, Lins
N. American Cancer Society guidelines for the early detection of prostate cancer; update 1997. CA Cancer J Clin
1997;47:261–4.
W: Cancer
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