Improved CRC Prognosis Goes Beyond the Success of Screening, Say Experts

Two health policy researchers, both physicians, have cautioned clinicians to tone down the perceived benefits of earlier screening in colorectal cancer (CRC) as being responsible for the positive trends that have been witnessed with the disease.

In their commentary in the New England Journal of Medicine, H. Gilbert Welch, MD, MPH, and Douglas J. Robertson, MD, MPH, both from the Dartmouth Medical School, appreciate the impact that screening has had on CRC incidence and mortality. The authors reference multiple trials that established the positive impact of screening:

• Fecal occult blood testing resulted in a 5% decrease in incidence and a 14% decrease in mortality due to CRC.
• Sigmoidoscopy resulted in a 28% reduction in mortality and 18% reduction in incidence.

However, when the authors evaluated the overall disease trend over nearly 40 years, between 1975 and 2012, among adults older than 50 years, they observed a 40% reduction in incidence since 1975. Additionally, CRC-related death reduced by more than 50% during that period, they write.

What the authors question is the timing of the observed trends, considering the delayed adoption of CRC screening in the clinic—only 23% of those 50 years and older were screened in 1987 and only 50% in 2005. Accounting for the lag time in the effect on mortality, “it’s hard to imagine a substantial screening effect at the population level showing up much before this new millennium started,” according to the authors. They propose the following to explain the decrease in mortality:

• Improved treatments. Improvements in surgical techniques, peri- and post-operative care, and better drugs. Additionally, adjuvant chemotherapy in patients with regional disease has been proven to reduce long-term mortality.
• Earlier detection, even without screening for disease. Endoscopy has lowered the threshold for directly examining the colon in people with possible symptoms of cancer. This allows identifying the disease at an early stage, so patients stand a chance for better prognosis.
• Lower incidence, period. Reduced incidence itself could be a significant determinant of outcomes. The authors believe that awareness in the population about the harms of bad dietary habits (smoked and cured meats) or changes in the gut flora with the widespread use of antibiotics could be likely reasons.

At the recently held annual meeting of the National Comprehensive Cancer Network, Alan P. Venook, MD, professor of Clinical Medicine at the University of California, San Francisco, however explained that despite the advances in understanding CRC and the improved treatments, success—measured in terms of mortality—has been rather insignificant. “There have been significant improvements in diagnosis and imaging techniques over the past few years, which can aide decisions on who could gain from surgery. However, a sum of all treatments that have been developed over the last decade finds that 10 months [overall survival] seems the most that has been achieved, although progression-free survival keeps improving.”

Welch and Robertson warn that exaggerating the benefits of screening could result in unnecessary follow-up colonoscopies in the older population, which might even cause harm.

Reference

Welch HG, Robertson DJ. Colorectal cancer on the decline—why screening can’t explain it all. N Engl J Med. 2016;374:1605-1607. doi:10.1056/NEJMp1600448.