Late diagnosis outweighs harm of breast cancer overdiagnosis

WOMEN who avoid mammograms due to fear of overdiagnosis and overtreatment are dicing with death as early cancer detection outweighs harms and saves lives.

A report released in the Medical Journal of Australia highlights that while overdiagnosis of breast cancer may be an inevitable consequence of the national screening program, this will never outweigh the harms caused by late diagnosis of the disease.

“Harms can range from the psychological stress of receiving a diagnosis through to the potential for complications and adverse effects of diagnostic procedures or treatments. However, the challenge is that for any individual, it is not possible at diagnosis to determine whether their cancer is overdiagnosed or not. The cancers that are overdiagnosed are indistinguishable from other cancers histologically,” authors led by Dr Vivienne Milch, Medical Director of Cancer Australia, wrote.

Cancer Australia has estimated that for every 1000 Australian women screened for breast cancer every two years from age 50 to 74 years, around eight breast cancers may be found and treated which would not otherwise have been found in a woman’s lifetime. An equivalent number of breast cancer deaths would be avoided in these women.

“Based on current international evidence, if left untreated, more than 90 per cent of cancers found through routine screening would progress and become symptomatic and be potentially lethal, depending on modelling assumptions,” Milch and colleagues wrote.

“These estimates are indicative of the scale of risk of developing a symptomatic breast cancer which could be detected earlier through screen detection. Screen-detected cancers are found at an earlier stage and tend to be smaller; treatment guidelines advise less extensive surgery and reduced need for adjuvant treatments, as well as being associated with improved survival.”

The authors highlighted the need to distinguish between formal screening programs such as the national breast screening program, and informal or opportunistic approaches to early detection, such as prostate-specific antigen (PSA) testing in prostate cancer.