This post is prompted by a new study [B6].
I use NSAIDs maybe once or twice a year, in a bad year. I have never been tempted by prophylactic use of aspirin - even low-dose.
Aspirin has been around for well over a century (since 1899), so never needed U.S. FDA approval. Some say that if it were a new drug, it could never be approved. It accounts for a sizeable number of ER visits. The fathers of two friends who were taking baby aspirin daily, both ended up in ER hell in the middle of the night because of blood in their toilet bowls. For some, it can be rough on the stomach. & it can damage the kidneys.
But chronic use of aspirin is widespread & there are positive things to report.
How might aspirin help improve survival? As a NSAID, aspirin might extend life by reducing inflammation. However, I doubt that a daily low-dose aspirin is up to the job, since cancer is a seriously inflammatory disease. Also, if aspirin could lower inflammation significantly, it would likely lower PSA. This might lead to a delay in PCa detection, which would not be expected to improve survival. More likely, IMO, aspirin might improve survival by reducing metastases.
An issue with aspirin use, as with statin or Metformin use, is that the users might have a different PCa risk profile, unrelated to aspirin itself. Non-users might be expected to have less cardiovascular disease risk, but the population would also include those not able or disinclined to take aspirin. And while the user population would be expected to mostly contain men with cardiovascular problems, it would also contain cautious health-conscious healthy men.
[A] Metastatic PCa & aspirin use.
There is a widely held theory that abnormal coagulation assists in metastasis, & that micro-clots might even be essential for the survival of circulating tumor cells. Coagulation is a complicated process involving many factors, but there are two main events: (i) the aggregation of platelets followed by (ii) the acretion of fibrin. Aspirin inhibits the clumping of platelets at low doses.
It is often observed that men with PCa have a higher risk of cardiovascular disease. The PCa population might therefore contain a significant percentage of men using daily aspirin for CVD reasons. Men who began using aspirin regularly before PCa diagnosis might have the best chance of preventing metastases, if aspirin is indeed protestive.
However, it is possible that aspirin users might also be more inclined to have regular PSA tests, & might be diagnosed earlier. That could have an impact on treatment outcome, i.e. fewer mets.
[A1] (2002 - U.S. - Health Professionals Follow-up Study [HPFS] - Giovannucci)
A "cohort of 47,882" "2,479 new cases of prostate cancer were ascertained. Of these, 608 were diagnosed as advanced (extraprostatic) prostate cancer and 258 as metastatic prostate cancer. We found no association between aspirin use and total prostate cancer."
But: "For metastatic prostate cancer, we observed a suggestive decrease in risk among men reporting greater frequency of aspirin use. The multivariate relative risk of metastatic prostate cancer among men using aspirin 22 or more days/month was 0.73 ... compared with nonusers."
[A2] (2011 - Health Professionals Follow-up Study [HPFS] - Giovannucci - again)
"In a prospective cohort study of 51,529 health professionals": "A total of 4,858 men were diagnosed with prostate cancer during the 18-year study period. Men taking ≥ 2 adult-strength aspirin tablets a week had a 10% lower risk of prostate cancer ... For regionally advanced cancer, we observed no significant associations with aspirin use. For high-grade and lethal disease, men taking ≥ 6 adult-strength tablets/week experienced similar reductions in risk (HR=0.72 ...)"
"For lethal prostate cancer (M1 at diagnosis or the development of bony metastases or fatal prostate cancer during follow-up), we observed a significant inverse trend ... for increasing number of tablets per week whereby men who consumed less than two adult-strength tablets per week (equivalent to one baby aspirin daily) had a non-significant 3% lower risk of lethal prostate cancer ... that further decreased to 20% for 2–5 tablets a week ... and 29% ... for 6 or more tablets per week, when compared to non-users."
[A3] (2012 - Health Professionals Follow-up Study [HPFS] - Chan (& Giovannucci)
"This is the first study reporting on aspirin consumption after a prostate cancer diagnosis and its association with the development of lethal prostate cancer. We observed no association between post-diagnostic aspirin use and metastatic or fatal prostate cancer."
A "potential mechanism for reducing fatal disease may be through aspirin's anti-platelet effects to reduce blood–borne metastases. One may speculate that such metastases may have already occurred by the time of diagnosis, eliminating aspirin's potential effect through that mechanism."
"Our data do not support an association between aspirin use after a prostate cancer diagnosis and the development of lethal prostate cancer."
However, one might argue that there is benefit in preventing further metastases. IMO.
[A4] (2013 - Swedish Prescribed Drug Register)
(Amazing that the Swedes can track low-dose aspirin use!)
"Except for a borderline result in prostate cancer (OR ∼0.9 ...), aspirin use was associated with a lower rate of metastatic disease (ORs ∼0.6–0.8) {for colorectal, lung and breast cancers}."
"In summary, we found evidence that the use of low-dose aspirin in the year prior to diagnosis was associated with better tumour extent for colorectal and lung cancers, but not for prostate and breast cancers, and was associated with lower metastatic disease for colorectal, lung and breast cancers."
[A5] (2014 - U.S.)
"We hypothesized that {anticoagulant} therapy confers a freedom from biochemical failure (FFBF) and overall survival (OS) benefit when administered with radiotherapy in patients with high-risk PC."
"Aspirin use was ... associated with reduced rates of distant metastases at 5 years (12.2% vs. 26.7% ...)"
"On subset analysis of patients with Gleason score (GS) 9-10 histology, aspirin resulted in improved 5-year OS (88% vs. 37% ...)" !!!
[A6] (2015 - U.S. - African American men )
"We identified 289 African American men with prostate cancer who were treated with definitive radiation therapy to a dose of ≥7560 cGy."
{The authors tried to make this hard to read. "ASA+" means aspirin users. "DMPFS" is distant progression-free survival. "PCSS" = prostate cancer-specific survival.}
"ASA use was associated with a significant reduction in biochemical recurrences (hazard ratio [HR] 0.56 ...). The 7-year DMPFS was 98.4% for ASA+ and 91.8% for ASA- men ... On multivariate analysis, ASA use was associated with a decreased risk of distant metastases (HR 0.23 ...). The 7-year PCSS was 99.3% for ASA+ and 96.9% for ASA- men ..."
[B] Survival / Mortality.
Some metastases studies in section [A] also report on lethal PCa, but the following survival/mortality papers make no mention of metastases. Even so, lethal PCa is largely due to metastatic disease.
[B1] (2012 - U.S.)
"This study comprised 5,955 men in the Cancer of the Prostate Strategic Urologic Research Endeavor database with localized adenocarcinoma of the prostate treated with radical prostatectomy (RP) or radiotherapy (RT). Of them, 2,175 (37%) were receiving ACs {anticoagulants} (warfarin, clopidogrel, enoxaparin, and/or aspirin)."
"AC therapy, particularly aspirin, was associated with a reduced risk of {prostate cancer-specific mortality} in men treated with RT or RP for prostate cancer." "Multivariable analysis indicated that aspirin use was independently associated with a lower risk of {prostate cancer-specific mortality} (adjusted hazard ratio, 0.43 ...)"
[B2] (2012 - U.K.)
"Post-diagnostic low-dose aspirin use was identified in 52 % of 1,184 prostate cancer-specific deaths and 39 % of 3,531 matched controls ..."
"Compared with no use, patients with 1-11 prescriptions and 12 or more prescriptions had adjusted ORs of 1.07 ... and 0.97 .., respectively."
"We found no evidence of an association between low-dose aspirin use before or after diagnosis and risk of prostate cancer-specific mortality, after potential confounders were accounted for, in UK prostate cancer patients."
Prescriptions for low-dose aspirin?
{After 43 years in the U.S., people still ask me where I am from. But to the English, I now sound like an America. On a vacation in England in 2004, my wife wanted some low dose aspirin for the return flight. (Her brother & father had both died because of blood clots.) So we went into 'Boots, the Chemist" but could not find the stuff. I approached someone who seemed to be in charge, & explained that we were looking for Baby Aspirin. She sighed, & looked at me as if to say "Americans & their infantile euphemisms!." "You mean 75 mg aspirin!" If I had my wits about me, I would have said: "No, no - 81 mg aspirin.", which is the U.S. low dose. Anyway, she walked over to a locked cabinet & found what we needed. No prescription required.}
[B3] (2014 - Ireland)
Prescriptions again - but a different conclusion.
"Men with stage I-III prostate cancer were identified from Irish National Cancer Registry records, which have been linked to national prescribing data from the Irish General Medical Services scheme. Aspirin use in the year preceding prostate cancer diagnosis was identified from this linked prescription-claims data."
"In adjusted analyses, aspirin use was associated with a small, but non-significant, reduced risk of prostate cancer-specific mortality (HR = 0.88 ...)"
"In dose-response analyses, stronger associations with prostate cancer-specific mortality were observed in men with higher aspirin dosing intensity (HR = 0.73 ...) and in men receiving >75 mg of aspirin (HR = 0.61 ...)"
So the dose seems to matter. Note that a low dose is sufficient to prevent platelet aggregation, but an increasing dose would have more effect on inflammation.
[B4] (2014 - U.S. - men with nonmetastatic prostate cancer)
"... the Cancer Prevention Study-II Nutrition Cohort in 1992 or 1993 and June 2009. Aspirin use was reported at enrollment, in 1997, and every 2 years thereafter. During follow-up through 2010, there were 441 prostate cancer deaths among 8,427 prostate cancer cases with information on prediagnosis aspirin use and 301 prostate cancer deaths among 7,118 prostate cancer cases with information on postdiagnosis aspirin use."
Modest protection against lesser cancer, but:
"... among men diagnosed with high-risk cancers (≥ T3 and/or Gleason score ≥ 8), postdiagnosis daily aspirin use was associated with lower {prostate cancer-specific mortality} (HR = 0.60 ...), with no clear difference by dose (low-dose, typically 81 mg per day, HR = 0.50 .., higher dose, HR = 0.73 ...)"
[B5] (2014 - Canadian study using UK data)
Similar to [B2] - failed to find benefit.
[B6] (2017 - U.S. - Physicians' Health Study )
"In 1981/82, the Physicians' Health Study randomized 22 071 healthy male physicians to aspirin, β-carotene, both, or placebo. After the trial ended in 1988, annual questionnaires have obtained data on aspirin use, cancer diagnoses, and outcomes up to 2009 for the whole cohort, and to 2015 for PC patients."
"502 men developed lethal PC by 2009"
"Current and past regular aspirin was associated with a lower risk of lethal PC (current: HR 0.68 ... past: HR 0.54 ... compared to never users."
"In the survival analysis, 407/3277 men diagnosed with nonlethal PC developed lethal disease by 2015. Current postdiagnostic aspirin was associated with lower risks of lethal PC (HR 0.68 ...) and overall mortality (HR 0.72 ...)"
-Patrick
[A1] cebp.aacrjournals.org/conte...
[A2] ncbi.nlm.nih.gov/pmc/articl...
[A3] cancerpreventionresearch.aa...
[A4] ncbi.nlm.nih.gov/pmc/articl...
[A5] ncbi.nlm.nih.gov/pmc/articl...
[A6] ncbi.nlm.nih.gov/pubmed/264...
[B1] ncbi.nlm.nih.gov/pubmed/229...
[B2] ncbi.nlm.nih.gov/pubmed/243...
[B3] ncbi.nlm.nih.gov/pubmed/243...
[B4] ncbi.nlm.nih.gov/pubmed/253...