Colon and
lung cancer patients who regularly took low-dose aspirin before their diagnosis
tended to have less advanced tumours, in a new study. Scientists already knew
that aspirin was tied to a decreased risk of death for people with colon
cancer, said senior author Yudi Pawitan.
"We showed evidence that it is also beneficial for lung cancer, and has
both early and late protective effects," Pawitan, of the department of
medical epidemiology and bio-statistics at the Karolinska Institutet in
Stockholm, Sweden, told Reuters Health.
However, the finding doesn't mean everyone should be taking aspirin to ward off
advanced cancer, researchers said. Pawitan and his co-authors analysed data
from Swedish cancer and prescription drug registries that included 80 000 patients
with colorectal, lung, prostate or breast cancer.
One in four people with colorectal, lung or prostate cancer had regularly taken
low-dose aspirin before being diagnosed – typically one 75-milligram tablet per
day – compared to about one in seven breast cancer patients.
Findings
The researchers found 20% to 40% fewer colon, lung and breast cancer
patients who had taken aspirin had tumours that had spread to other areas of
the body than those who had not taken aspirin.
For example, 19% of regular aspirin users with colon cancer had
metastatic disease, compared to close to 25% of non-users. Tumours on
average were smaller and less advanced among aspirin users with colon and lung
cancer, but not those with breast or prostate cancer, according to results
published in the British Journal of Cancer.
"The fact that they did not find a similar result for breast and prostate
cancer does not exclude the possibility that aspirin may work at a different
point in the cancer process for those cancers," said Dr Michelle Holmes,
who researches cancer risk factors at Brigham and Women's Hospital and Harvard
Medical School in Boston.
"This paper confirms what is already known: aspirin use is associated with
decreased risk and better survival," said Dr Gerrit-Jan Liefers, a cancer
surgeon at Leiden University Medical Centre in The Netherlands.
Liefers said it was interesting that the study found aspirin was associated
with smaller tumours but not with whether nearby lymph nodes were involved,
which can be an indicator of a cancer's aggressiveness.
Mechanism not fully understood
That's a new finding and will fuel more discussion about how aspirin works,
Liefers, who was not involved in the study, told Reuters Health. "The
mechanism is not fully understood," Pawitan said. Some researchers believe
the anti-inflammatory and blood thinning effects of aspirin contribute to the
lowered risk of certain cancers, he said.
Researchers also aren't sure why aspirin would end up being beneficial for
people who develop colon and lung cancer and not for breast or prostate cancer
patients, though breast and prostate cancers often have more hormonal factors
involved, he said. It is possible that people who regularly take aspirin tend
to have different lifestyles than those who don't, and some other aspect of
their lives contributes to their differing cancer risks, Liefers said.
The researchers in this study accounted for age, gender and socioeconomic
status, but ruling out all other factors in this type of population-based study
is always difficult, he said.
Trials that randomly assign people to take aspirin or not will better be able
to account for lifestyle differences and are already in the early stages in
Asia, The Netherlands and the UK, he said. Without those randomised controlled
trials, researchers can't say aspirin caused the reduced cancer risks observed
in this study, Holmes told Reuters Health.
Regular use of aspirin has been shown to increase the chance of
gastrointestinal bleeds."Because it has side effects, it would be
difficult if not impossible to prescribe aspirin to all people," Pawitan
said. Ideally, only those at high risk for developing cancer would take
aspirin. "Whether such an approach would benefit society as a whole
deserves further studies," he said.