Doctors believe they have
found telltale signs that can indicate whether breast or prostate malignancies
will remain dormant or develop into aggressive cancers.
These indicators – called
"biomarkers" – are found in the blood or tissues of people with
breast or prostate cancer. Researchers hope to one day use them to develop
tests that will determine the cancer treatment each patient will need.
"It's a dream, I would
say, at the moment. And it's a hope," Dr Clifford Hudis, president of the
American Society of Clinical Oncology (ASCO), said of the potential for using
biomarkers to help determine a person's risk of aggressive cancer. "But
it's not yet clinically validated, and it's not useful yet for patients."
Two research teams are
scheduled to present their findings on possible biomarkers for breast and
prostate cancer this week at the International Conference on Frontiers in
Cancer Prevention Research, hosted by the American Association for Cancer
Research, at the National Harbor in Oxon Hill, Maryland.
Doctors with the University
of Pennsylvania reported that the presence of a protein called Vav2 in breast
tissue might indicate whether a precancerous condition called ductal carcinoma
in situ, or DCIS, will develop into invasive breast cancer.
Chromosomes might provide evidence
Meanwhile, Johns Hopkins
researchers said chromosomes in a man's blood might provide evidence that a
prostate cancer will develop in an aggressive manner.
There is widespread concern
that in both DCIS and prostate cancer, doctors tend to over treat patients.
Two-thirds of DCIS cases
never progress to full-fledged invasive cancer, ASCO's Hudis said, "which
means when we treat DCIS, we are treating many people who would never have
developed invasive cancer."
And few men with prostate
cancer actually die as a result of the cancer, which has prompted much debate
over whether doctors should treat it, said William Phelps, programme director for
the American Cancer Society. The available treatments often lead to unpleasant
side effects such as incontinence and impotence.
themselves are not very good," Phelps said of prostate cancer. "If
the treatments were fairly undamaging, you'd just say, 'Well, let's treat
researchers examined 211 remnants of tissue samples that had been taken to
diagnose breast cancer. Of the samples, 42 were normal breast tissue, 71 were
DCIS and 98 were invasive breast cancers.
DCIS involves the presence
of abnormal cells inside a milk duct in the breast. In "pure" DCIS,
the cells have not become cancerous and started to spread, said senior research
investigator Marina Guvakova, an adjunct assistant professor in the department
of surgery at the University of Pennsylvania.
However, there also are
forms of DCIS that involve either fully invasive cancer or micro-invasive
cancer, in which fewer than 10 percent of the abnormal cells have spread beyond
the original tumour.
The doctors found that the
amount of Vav2 in pure DCIS is as low as in normal breast tissue, but that
presence of the protein gradually increased in DCIS with micro-invasive cancer.
The highest levels of Vav2 were found in DCIS with invasive cancer.
"Those lesions are
twice as likely to have associated invasive breast cancer as lesions with low
expression of Vav2," Guvakova said.
revealed that the ability of Vav2 to predict progressive cancer in DCIS was
0.71. A value of 1 means the marker has a perfect discriminating power, and a
value of 0.5 means that the marker's discriminating power is no better than
"It is, in statistical
terms, considered a very good predictor," Guvakova said. "It's
definitely not by chance."
Their findings have not
been published, but once that is accomplished the team will begin designing a
study that would attempt to predict the behaviour of DCIS in current patients,
The Johns Hopkins research
into prostate cancer focused on telomeres, which are sequences of genetic
material located at the ends of chromosomes, that protect them. They function
in much the same way that the plastic tips at the ends of a shoelace protect
the lace from unravelling.
Doctors examined the DNA in
immune cells drawn from blood samples provided by 441 men who later developed
prostate cancer, as well as 421 men who did not develop prostate cancer.
The researchers found that
among the men who developed prostate cancer, those with the shortest telomeres
in their immune cell chromosomes were more than twice as likely to have
developed aggressive prostate cancer compared to those men who had the longest
Smoking appears to play a
strong role. When the researchers narrowed their analysis down to current or
former smokers, they found that those with the shortest telomeres in their
immune cells were more than four times as likely to have developed aggressive
"We don't yet know why
having short telomeres in blood leukocytes [white blood cells] seems to be
associated with risk of aggressive prostate cancer," researcher Elizabeth
Platz, a professor in the department of epidemiology at Johns Hopkins Bloomberg
School of Public Health in Baltimore, said in a conference news release.
"It may tell us about
a person's exposure to factors that increase their risk of prostate cancer, or
it may be an indication of an inherent inability to maintain telomere length,
which could put them at increased risk for this disease," Platz said.
"If so, it might be that measuring telomere length in blood leukocytes could
even predict risk of many different forms of cancer."
Because the studies were
presented at a medical meeting, the data and conclusions should be viewed as
preliminary until published in a peer-reviewed journal.
For more about breast
cancer, visit the US National Cancer Institute.