Thursday, December 6, 2012

Top Cancer Prevention and Screening Advances in Context

Earlier this week, the American Society of Clinical Oncology (ASCO) published their 2012 annual report on key clinical advances in cancer. Though the document's largely focussed on breakthroughs in treatment and diagnosis, it does highlight three important results in prevention and screening.

Colon Cancer Screening
First are findings from the Prostate, Lung, Colorectal, and Ovarian Cancer (PLCO) Screening Study that further bolstered the benefits of colon cancer screening.  We've written extensively on this blog about the benefits of regular screening tests for colorectal cancer -  whether with the fecal occult blood tests (FOBT), sigmoidoscopy, colonoscopy, or other recommended tests.  Data have consistently borne out the benefits of screening, and not just for finding cancer early, when it's more treatable, but in actually preventing disease in the first place.  The large study by Schoen and colleagues highlighted by ASCO found that screening with flexible sigmoidoscopy at regular intervals could lower the risk of dying from colon cancer by 26 percent and of developing colon cancer by 21 percent.  Though similar to colonoscopy, flexible sigmoidoscopy is a less involved procedure that is quicker to perform and only examines the lower part of the intestine, rather than the full length as with colonoscopy.

Of course, compelling findings alone don't insure that people will follow a new healthy behavior, like getting screened.  Moving from science to action to real world impact usually takes a broad-based, concerted, and often long-term effort to succeed.  Years after colon cancer screening won approval for coverage by Medicare and other health insurers, rates of use still vary greatly across the US.  Massachusetts had the highest uptake of screening in the nation in 2010, capping off a multi-year effort by state and local governments, universities, health insurers, physicians, NGOs and others to make a screening a priority as well as a reality in the state - a successful effort highlighted in a previous post.

Lung Cancer Screening
Next on the ASCO list are findings also confirming something long-suspected, that regular screening with chest X-rays doesn't lower lung cancer mortality rates. Though it seems intuitive that a regular X-ray would help find lung cancer early when it's most treatable - and therefore save lives - the numbers just did not support this.  In a study of over 150,000 people, half of whom received annual chest x-rays over a four year period and half of whom did not, there was no difference between the two groups in the rates of people dying from lung cancer.

Unfortunately, this is how things often play out for potential cancer screening tests.  While on paper they can seem promising, there are many avenues where new tests can fall short and miss a key criteria for an effective test: saving lives.  (See our Cancer Screening page for more on why finding good, new tests can be difficult.)

There is, however, some promise on the lung cancer screening front with spiral CT scans.  In smokers, results from the Lung Cancer Screening Study found that screening with spiral CT could reduce deaths from lung cancer by 20 percent.  It's a significant number but many unanswered questions remain about who exactly should be screened, how often, and what the risks may be.  Tobacco prevention and cessation efforts remain the surest and most cost-effective way to lower the death rate from lung cancer, as we touched on in a previous post.

Regular Aspirin Use
Finally, aspirin.  A new analysis of over 51 different studies found that regular aspirin use for just three years could lower the risk of developing cancer by around 25 percent, and the risk of dying from cancer by 15 percent.  With five or more years of use, cancer deaths dropped by 37 percent. These findings build on results we've written about previously (here, here, and here) showing that long term use of aspirin can significantly and sustainably lower the risk of colon cancer (see figure).  This new analysis, though, shows benefits from relatively short-term use, and given the heart-health benefits of aspirin - and some intriguing new results for liver cancer - it seems it may be time to reassess prevention-oriented recommendations for aspirin that currently largely apply just to those at high risk of heart attack and begin to consider it for a broader swath of the population as well.

Challenges are a constant in the quest to prevent cancer.  But each year we make progress, honing our understanding of the issues and crafting better and more effective ways to improve health and lower risk.  This past year was no exception, and it seems assured that 2013 won't be either.

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