Is Aspirin a Cost-Effective Addition to Colorectal Cancer Screening?

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The summary below is from the full report titled "Aspirin as an Adjunct to Screening for Prevention of Sporadic Colorectal Cancer. A Cost-Effectiveness Analysis." It is in the 6 November 2001 issue of Annals of Internal Medicine (volume 135, pages 769-781). The authors are U Ladabaum, CL Chopra, G Huang, JM Scheiman, ME Chernew, and AM Fendrick.

What is the problem and what is known about it so far?

Colorectal cancer is cancer of the colon (large intestine) or rectum. Screening decreases deaths from colorectal cancer by detecting precancerous abnormalities (polyps) and removing them before they become cancer and by detecting cancer in an early stage when it can still be cured with surgery. Screening tests include fecal occult blood testing (FOBT), flexible sigmoidoscopy, and colonoscopy. FOBT uses a chemical reaction to detect blood hidden in stool. Polyps and colorectal cancers can cause blood to leak into the stool, so a positive result on FOBT suggests the need for further testing. Flexible sigmoidoscopy involves looking into the rectum and lower colon through a tube-shaped instrument; colonoscopy uses a similar but longer instrument to look at the entire length of the colon. While it is not clear which screening strategy makes the most sense in terms of costs and associated benefits, it is clear that some form of routine screening is favorable after age 50 in terms of health benefits and economics. Taking an aspirin a day may also help to prevent colorectal cancer. However, the degree of benefit from aspirin is unclear, and aspirin can cause bleeding complications.

Why did the researchers do this particular study?

To find out whether adding daily aspirin to regular colorectal cancer screening makes sense in terms of health benefits and costs.

Who was studied?

Rather than studying actual patients, the researchers used computers to simulate what would happen to a "virtual" group of patients 50 to 80 years of age. They assumed that patients had no special risks for colon cancer.

How was the study done?

The researchers used published information to estimate what might happen (and how much it would cost) if patients took aspirin in addition to having regular screening for colorectal cancer. They put these estimates into a computer model and calculated how much adding aspirin would cost for each year of life it saves.

What did the researchers find?

The researchers found that using aspirin to prevent colorectal cancer in regularly screened patients costs more per year of life it saves than society typically finds acceptable. This is due in large part to the complications caused by aspirin.

What were the limitations of the study?

This study was a computer simulation, so we cannot be sure what the results would be with actual patients.

What are the implications of the study?

Aspirin alone cannot be considered a substitute for colorectal cancer screening. In terms of costs and benefits, it does not make sense to prescribe aspirin primarily to prevent colorectal cancer in patients who get regular screening.