SA JOURNAL OF DIABETES & VASCULAR DISEASE
DRUG TRENDS
Substantial evidence for colorectal cancer reduction with daily low-
dose aspirin
H
igh-dose aspirin (
≥
500 mg daily) taken
for a period of five years has been shown
in long-term follow-up studies to reduce the
risk of colorectal cancer in the next decades
of the patient’s life. However, the greater risk
of bleeding complications at this high dose
reduces aspirin’s potential in primary preven-
tion of cancers.
New data from four trials of aspirin,
1
using
daily dosages from 75 to 300 mg were com-
pared to the high-dose aspirin studies and
showed:
• 75 mg aspirin taken daily is as effective as
high-dose aspirin in reducing the 20-year
incidence of colorectal cancer (by 30%) if
taken for approximately five years.
• Not only did the lower dose of aspirin
reduce the incidence of these cancers,
it also reduced mortality from colorectal
cancer.
• The reduction in fatal colorectal cancer
tended to be greater than the reduction in
incidence.
• Very low daily doses of aspirin tended to
not be effective in the prevention of colo-
rectal cancer.
• The reductions in both incidence and death
due to colorectal cancer were greater for
proximal cancer tumours than distal colon
or rectal tumours.
• The reduction in 20-year risk of death
due to colorectal cancer was larger than
expected.
• Larger doses, above 300 to 1 200 mg daily,
did not confer any additional benefits in
terms of reduced incidence or deaths from
colorectal cancer.
The long-term absolute risk reduction of 1–5%
after long-term, low-dose aspirin treatment
has implications for clinical practice. It adds
to the primary preventative benefits of aspirin
and may tip the balance in favour of aspirin
compared to newer anti-platelet agents.
2
J Aalbers, Special Assignments Editor
1.
Rothwell PM, Wilson M, Elwin CE, Norrving B,
et
al
. Long-term effect of aspirin on colorectal cancer
incidence and mortality: 20-year follow-up of five
randomised trials.
Lancet
. Published online Oct 22,
2010. DOI:10.1016/S0140-6736(10)61543-7.
2.
Benamouzig R, Uzzan B. Aspirin to prevent
colorectal cancer: time to act?
Lancet
. Published
online Oct 22, 2010. DOI:10.1016/50140-
6736(10)61509-7.
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