A new review of studies supports the idea that low daily doses of aspirin reduce the risk of certain cancers. A relative benefit, to be weighed against the risks associated with the adverse effects of the analgesic.
Colorectal cancers, breast cancers: new evidence of benefit
Many studies have already established that adults who take aspirin daily (for to inform blood clots) have fewer risk of colorectal cancer than adults of the same age who do not follow this “diet”. Until now, it has been estimated that, in the populations studied, a daily intake of an aspirin tablet is associated with a reduced risk “by 20% to 40%” – which is confirmed by the new meta-analysis.
However, as we explained in May 2016 on the plateau of Health magazine, all aspirin consumers are not equal when it comes to colorectal cancer: some genetic profiles derive more benefit than others from this treatment.
By putting into the equation fourteen observational studies (long-term follow-up of patients), the authors confirm “in the general population” a reduction in the risk of breast cancer, in a range of values between 10% and 47%. Note, here again, that certain genetic profiles could be disadvantaged.
A confirmed effect against the spread of metastases
Several scattered studies suggested that if cancer develops, the risk of developing metastases was lower in people who used low doses of aspirin on a daily basis for a long time. The meta-analysis broadly validates these observations, establishing a risk reduction of at least 46%.
Insufficient data on other cancers
A few optimistic studies on the benefit of aspirin for the prevention of prostate cancer have been in the media in recent years. The new meta-analysis shows, however, that in view of the whole, nothing yet formally demonstrates a preventive effect.
Regarding other types of cancer, too few studies have yet been carried out to formally conclude that there is an association (positive or negative) between taking aspirin and their risk of occurrence. However, an effect seems likely for certain leukemias, as well as on the spread of endometrial cancer.
The meta-analysis does not review current suspicions about the links between frequent aspirin intake and increased risk of kidney cancer.
But proven hemorrhagic risks in some cases
New meta-analysis looked at risk of bleeding in patients already have cancer who would take aspirin (a medicine that has the same property of thinning the blood). The data collected did not make it possible to conclude that this risk existed – without excluding it.
On the other hand, the study does not address the issue of bleeding risks associated with consumption preventive aspirin. However, according to other studies, a daily consumption of aspirin indeed increases by more than 50% the risk of intracranial hemorrhages and gastrointestinal hemorrhages, being able in particular to cause anemia and ulcers in the stomach.
These bleeding risks are, until proven otherwise, particularly important for the elderly, or those with a history of digestive bleeding, kidney failure or liver problems, as well as for heavy smokers and people who consume a lot of alcohol.
See also: Long-term aspirin: risks for those over 75
So should aspirin be prescribed as a preventive measure against cancer?
As the authors of this new work point out, the cause and effect link between taking aspirin and reducing the risk of cancer has not yet been formally established. Indeed, it cannot be ruled out that the pathologies which make it necessary to take aspirin daily are, in themselves, associated with lower risks of cancer …
The benefit / risk ratio of taking aspirin daily remains, in fact, still very controversial. Some researchers still believe that, for patients in good health and not presenting any particular risk factors, it would present more risks than benefits.
However, some studies argue for the benefit of such a treatment “in people aged 50 to 65 ”. Followed over 10 years, it would prevent about 8% of cancers and strokes in this age category. The reduction in mortality at age 20 is estimated at around 4%. An analysis of the scientific literature gave rise, in mid-April 2016, to a (highly targeted) update of official recommendations in the United States (see this box).
Study: PC Elwood, et al. “Systematic review update of observational studies further supports aspirin role in cancer treatment: Time to share evidence and decision-making with patients?”. PLOS One, sept. 2018. doi:10.1371/journal.pone.0203957