Thursday, 22 October 2009

Rethinking strategies for breast and prostate cancer screening

Twenty years of screening for breast and prostate cancer—the most diagnosed cancers for women and men—have not brought the anticipated decline in deaths from these diseases, argue experts in an opinion piece published Wednesday in the Journal of the American Medical Association

In an article published yesterday (Oct 21, 2009) in JAMA, Laura Esserman et al, one of our UCSF breast surgeons, and leader of the ATHENA project in the University of California, discuss whether we should be reconsidering looking at our screening tools for both breast and prostate cancer, and be more intelligent in their use.

"Screening does provide some benefit, but the problem is that the benefit is not nearly as much as we hoped and comes at the cost of over-diagnosis and over-treatment," said Laura Esserman, MD, professor of surgery and radiology, director of the University of California, San Francisco (UCSF) Carol Franc Buck Breast Care Center.

We acknowledge that screening is not perfect, as there are a proportion of women who are screened but would never die of the disease (lead time bias). Also there are the group of women who present as interval cancers due to their very different biology. These women still get their mammograms at the proscribed times, but tend to develop cancer between their screening tests.

"We need to focus on developing new tools to identify men and women at risk for the most aggressive cancers, to identify at the time of diagnosis those who have indolent or 'idle' tumors that are not life-threatening,"

Periodic screening may find some tumors early, but patients may not be screened often enough for lethal tumors to be detected in time to prevent death, leading the authors to conclude: "Without the ability to distinguish cancers that pose minimal risk from those posing substantial risk and with highly sensitive screening tests, there is an increased risk that the population will be over-treated."

The authors suggested that to improve screening, "a new focus is recommended for research and care to identify markers that discriminate minimal-risk from high-risk disease (and) identify less aggressive interventions for minimal-risk disease to reduce treatment burden for patients and society."

The authors made the following recommendations for early cancer detection and prevention:
  • Develop tests to distinguish between low-risk and lethal cancers.
  • Reduce treatment for low-risk disease. “Diagnosing cancers that don't kill the patient has led to treatment that may do more harm than good,” they wrote.
  • Develop tools for physicians and patients to help them make informed decisions about prevention, screening, biopsy and treatment.
  • Offer treatments individually tailored to a patient's tumor.
  • Work to identify the people at highest risk for cancer and use proven preventive interventions.
As part of the ATHENA project we are looking at these aspects across the whole of the University of California medical centers (UCSF, UCLA, UC Irvine, UC Davis and UC San Diego).
This is a mix of researcher and clinicians who are trying to put research to clinical use (bench to bedside medicine)

Targeting screening tests to the at risk population may give better outcomes with fewer so called "false positives" from screening, thereby benefiting the screened women the most. It will also save us from overtreating some of the lower risk/indolent cancers that occur.

NCI commentary is available in their bulletin