Monday Pharmaceutical Mystery: Why is an Oncologist Prescribing Aspirin?

HL is a 35 year old male who comes to the pharmacy with a new prescription for acetylsalicylic acid (ASA) 650 mg qd #60. He asks for a price quote for the medicine. He says it is his cancer medication, and he is not sure he can afford it.

You see that the prescription is indeed written by an oncologist, and you know the indication for this medication at this dose. You ask HL if he has Lynch syndrome, a hereditary condition that puts young people at high risk for colon cancer. He says “yes.”

Then, you tell him the good news. The cash price for this cancer medication is less than $10 for an entire year’s supply. It is old fashioned aspirin, and the generic is just as good as the name brand.

Mystery: Since when is aspirin a cancer medication?

Solution: It was an accidental discovery, in 1988, when a large case-control study examined the use of several random medications and the occurrence of colorectal cancer. This study unexpectedly discovered that daily aspirin users had lower rates of colorectal cancer.¹

That discovery led to more studies, and in 2016 this information was examined by the US Preventative Services Task Force, a volunteer panel of national experts. The task force’s assessment and recommendations were published in JAMA Oncology.²

Task force investigators found that years of frequent aspirin use resulted in a reduction in the risk of developing both colorectal cancers (CRC) and esophageal cancers (19% and 15% respectively,). The task force also found that 8.0% of all GI tract cancers, and10.8% of CRCs could have been prevented with regular aspirin use.

According to the task force, protection against GI tract cancers occurs at relatively low doses of 0.5 to 1.5 standard tablets a week. The people studied used aspirin for various reasons such as cardiovascular protection, headache, arthritis, and musculoskeletal pain.²

More studies are needed to confirm the exact regimen needed for maximum results and specific risk reductions.

Patients who started taking aspirin after being diagnosed with a GI cancer lived twice as long as those who did not take aspirin. Specifically, after 5 years, survival was 75% among aspirin users, and 40% among non-aspirin users. The people studied had esophageal, colon, and rectal cancers.³ The study investigators speculated that aspirin prevents the circulating tumor cells from hiding inside the platelets. Therefore the immune system can attack and kill the cancer more easily.⁴

Pharmacists are the consumer’s advocate. It’s up to the pharmacist to give good advice on aspirin use.

Things to note:

• Investigators agree that going for a colonoscopy and having polyps removed will do way more to reduce the cancer occurrence than aspirin alone. Patients should not use aspirin in place of having polyps removed, but rather in addition to polyp removal.
• People need to take aspirin for several years before the protection kicks in. With continuous use, the protection increases and maxes out at 5-6 years. Also, after stopping aspirin, the protection continues for a couple years.
• Bleeding is a known adverse effect of aspirin use. GI bleeds and brain hemorrhages are especially concerns.

REFERENCES

• Kune GA, Kune S, Watson LF. Colorectal cancer risk, chronic illnesses, operations, and medications: case control results from the Melbourne Colorectal Cancer Study. Cancer Res. 1988; 48:4399. https://cancerres.aacrjournals.org/content/canres/48/15/4399.full.pdf
• Vilar E, Maresso KC, Hawk ET, et al. Aspirin for Cancer Prevention: One Step Closer. JAMA Oncol. 2016; 2(6): 770-771.
• Movahedi M, Bishop DT, Macrae F, et al. Obesity, Aspirin, and Risk of Colorectal Cancer in Carriers of Hereditary Colorectal Cancer: A Prospective Investigation in the CAPP2 Study [Published online ahead of print August 17, 2015]. J Clin Oncol. doi: 10.1200/JCO.2014.58.9952.
• European Cancer Congress (ECC) 2015: Abstract 2306. Presented September 28, 2015.