The studies were conducted by Professor Peter Rothwell of Oxford University. Rothwell and his team had previously published evidence indicating a daily low dose of aspirin can reduce a person’s long-term risk of dying from cancer, and that this benefit does not appear until about 8 to 10 years after starting the regimen.
However, according to Rothwell, "In particular, we show that aspirin reduces the likelihood that cancers will spread to distant organs by about 40-50%," said Rothwell, explaining this was just as important a finding because it is metastasis that commonly kills people with cancer. No drug has been shown before to prevent distant metastasis and so these findings should focus future research on this crucial aspect of treatment of patients with cancer that hasn't already spread."
This suggests that patients who have already received a cancer diagnosis could see benefits from taking aspirin following their diagnosis, as long as their cancer has not yet spread. Rothwell and colleagues claim that it is necessary for new trials to be conducted to confirm these benefits.
It is widely known that daily aspirin consumption is not without risks. There is an increased potential for internal bleeding, especially in the stomach. However, even in this area, Rothwell and his team reveal findings that indicate the harms may be less severe than previously thought. The risk of stomach bleeds appears to diminish with extended use and the risk of dying from a stomach bleed is no greater than with aspirin than with a placebo.
For the first study, Rothwell and colleagues collected data from 51 randomized clinical trials that looked to compare the effect of daily aspirin use with not taking any aspirin on cardiovascular events like heart attack and stroke. These trials also collected data on cancer.
From the results, it was established that aspirin lowered the risk of cancer mortality by 15%, and this reduction increased with long-term use. For example, those who took it for 5 years or more saw a 37% reduction in cancer risk.
Rothwell and colleagues also discovered that taking a low dose of aspirin every day did more than reduce deaths from cancer; it also reduced incidence. Following three years of an aspirin regimen, the reduction in cancer incidence was 23% in men and 25% in women.
In their second study, Rothwell and colleagues examined the impact of aspirin use on metastasis, an event where cancer spreads beyond its original site. In this study, the researchers pooled data from 5 large randomized UK trials that monitored aspirin use in preventing heart disease.
The results indicated that aspirin use led to a reduction in the risk of metastases occurring. The risk was lowered by 36% over the 6.5 year average duration of the studies, and did not vary by age or gender.
For their third study, Rothwell and colleagues again investigated aspirin and cancer risk. However this time they systematically reviewed observational studies instead of clinical trials where participants are randomly assigned to different treatment groups. This analysis confirmed their previous findings and found similar reductions in cancer risk.
Certain cancers also appear to respond more to aspirin use. Rothwell claims that in terms of controlling spread, their findings suggest that the largest effect was seen among esophageal and colorectal cancer. It also includes most breast and prostate cancers, and some lung cancers as well.