Aug. 14--A new study of prostate cancer suggests that a tumor's aggressiveness
is inherently fixed at the time of its appearance, although diet, lifestyle and
environmental factors may trigger progression of the disease in low-level cases.
The findings, published Wednesday in the journal Cancer Research, add to
mounting evidence that many small, slow-growing prostate tumors can be left in
the body and carefully monitored instead of being treated with surgery,
radiation, hormone therapy or drugs.
Doctors call this approach "active surveillance," and it's increasingly seen as
a way to reduce the risk that men will suffer side effects like incontinence and
erectile dysfunction after treating tumors that would not have killed them. The
National Cancer Institute estimates that 238,590 men will be newly diagnosed
with prostate cancer this year, though the tumors are generally slow-growing and
most patients will die of something else.
Researchers set out to determine whether prostate tumors begin as indolent
growths and become more dangerous over time, or whether their level of
aggressiveness remains constant.
To accomplish this, the study authors examined 1,200 cases of men who had their
prostates removed from 1982 to 2004 because of cancer. The sample consisted of
men who were diagnosed before and after the introduction of the
prostate-specific antigen test in the early 1990s, which became a popular tool
to diagnose prostate cancer in men who had not yet developed symptoms of the
The researchers focused on two measures that are often used to predict a tumor's
behavior. The first measure, stage, describes the extent to which a cancer has
spread. The second measure, Gleason score, describes just how normal or abnormal
cells are within the diseased tissue.
As expected, the incidence of advanced-stage cancers plummeted after the
introduction of PSA screening, because more cancers were caught early.
Late-stage cancers, defined as T3 or higher, made up 20% of the cases diagnosed
from 1982 to 1993, but constituted only 3% of the cases diagnosed from 2000 to
2004, the researchers discovered.
In contrast, the number of high Gleason grade cancers -- those above 8 -- held
relatively steady: They made up 25% of the sampling from 1982 to 1993, and
dropped to 18% in 2000 to 2004. That difference was not deemed statistically
The researchers determined that the cancer's aggressiveness must remain fixed;
otherwise, high Gleason scores would have dropped more sharply, in line with the
Study leader Kathryn Penney, an epidemiologist at Boston's Brigham and Women's
Hospital and the Harvard School of Public Health, said the results supported the
idea of active surveillance for most prostate cancer patients.
"This isn't a reason in and of itself to take active surveillance," she said.
"But if a patient's physician recommends active surveillance, and the patient
agrees, this finding can make a man feel more comfortable about making that
However, Penney acknowledged that there were still men with high grades of the
disease who survived and men with low grades who died.
"We think that while Gleason itself might be a fixed characteristic, there are
likely other factors that are playing a role," such as diet and lifestyle
factors like smoking, she said.
Dr. Robert Reiter, who directs the prostate cancer program at UCLA, said the
study was important because it addressed the fundamental question of whether
cancers become more aggressive as the months and years pass.
But the data showed that not all cancers were fixed, and that some did change.
The challenge for clinicians, Reiter said, was to "identify ones that have the
potential to morph over time versus those that do not."
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