Studies suggest that as many as 30% of the breast cancers discovered via mammograms in recent years may have been treated unnecessarily. Pictured, Dr. Gerald Iba checks mammograms at The Elizabeth Center for Cancer Detection in Los Angeles. Associated Press

…But while there have been large increases in cancers diagnosed early, the drop in cancer deaths has been smaller than expected. That is leading some experts to conclude that many early cancers aren’t life-threatening and others that are deadly are slipping through the cracks.

An estimated 85% of early prostate cancers are thought to be so slow-growing they wouldn’t cause harm in a patient’s lifetime, but about 90% of these men opt to treat them aggressively—despite the risk of side effects such as incontinence and impotence.

… Studies suggest that as many as 30% of the breast cancers discovered via mammograms in recent years may have been treated unnecessarily.

In skin cancers, the panel said 2.2 million Americans are diagnosed with basal and squamous-cell skin cancers annually, up more than 50% in the past decade. Many of those lesions are removed with surgery that can be disfiguring, though they are rarely fatal if left alone.

In lung cancer, CT scans find many more early-stage tumors than chest exams do, but the smallest have only a 1% to 5% chance of being cancer, the article says, which is why the U.S. Preventive Services Task Force recently recommended that only people at highest risk for lung cancer have CT screening routinely.

In thyroid cancer, diagnoses tripled in the U.S. in recent decades, thanks to ultrasound detection, but the death rate remained constant.

The panel said the overdiagnosis and overtreatment concern also extends to precancerous conditions that have only a small percentage chance of becoming cancer, such as Barrett’s esophagus (changes in the lining of the esophagus) and ductal carcinoma in situ (abnormalities in breast mik ducts), known as DCIS.

Nearly 50,000 women with DCIS in the U.S. are being treated each year, including 20,000 with mastectomies, against the possibility that it will develop into invasive breast cancer, yet the incidence of invasive breast cancer hasn’t dropped, the article noted”

Overdiagnosis: when finding cancer can do more harm than good

“What’s the evidence?

Some of the earliest evidence around overdiagnosis came from autopsy studies. Experts found undiagnosed cancers in people who had died from a cause other than cancer. This showed in some cases people can live out their life without ever knowing a cancer is there, or being harmed by it…

  • Thyroid cancer in South Korea – a true epidemic?
  • Breast screening: saving lives and balancing harms
  • Prostate cancer: why there’s no UK screening programme
  • Seek and you shall find