Reform needed to counter cancer overdiagnosis

A new study published in the Medical Journal of Australia has found Australians are increasingly being diagnosed with cancers that would not have caused any problems if left undetected or untreated, potentially exposing them to unnecessary surgeries and chemotherapy.

The researchers from the University of Sydney and Bond University are calling for greater vigilance in monitoring overdiagnosis and revised screening tests, and for urgent policy changes to address overdiagnosis in Australia.

The results suggest Australians are much more likely to experience a cancer diagnosis in their lifetime compared to 30 years ago.

The work draws on data from the Australian Institute of Health and Welfare to compare how the lifetime risk of five cancer types changed between 1982 and 2012.

The research was led by Professor Paul Glasziou,  Director of the Institute for Evidence-Based Healthcare at Bond University in conjunction with co-authors Professor Alexandra Barratt and Associate Professor Katy Bell of the University of Sydney’s Faculty of Medicine and Health and Associate Professor Mark Jones and Dr Thanya Pathirana of Bond University. 

Key findings

The figures suggest that in 2012, 24 percent of cancers or carcinomas were overdiagnosed in men.

These included:

• 42 percent of prostate cancers
• 42 percent of renal cancers
• 73 percent of thyroid cancers
• 58 percent of melanomas.

In women, 18 percent of cancers were overdiagnosed.

These included

• 22 percent of breast cancers
• 58 percent of renal cancers
• 73 percent of thyroid cancers
• 58 percent of melanomas.

The figures are significant because of the harm that can occur from cancer treatment of patients who would never have had symptoms in their lifetime.

“Cancer treatments such as surgery, radiotherapy, endocrine and chemotherapy carry risks of physical harms,” the authors of the study state.

“In the absence of overdiagnosis, these harms are generally considered acceptable. In the context of overdiagnosed cancers, however, affected individuals cannot benefit but can only be harmed by these treatments.”

Getting the balance right

Study co-author Associate Professor Katy Bell said that the findings also suggest an important role for health services such as the Australian Institute of Health and Welfare, in detecting potential overdiagnosis and alerting health policy decision-makers to the problem early on.

“Patterns of increased test use, cancer incidence, or treatment rates, without corresponding rises in mortality could indicate emerging areas of overdiagnosis,” she said.

The authors also refer to separate studies showing overdiagnosis could be associated with psychological problems.

“For example, men’s risk of suicide appears to increase in the year after receiving a prostate cancer diagnosis.”

Professor Glasziou said increasing rates of diagnosis were a result of improvements and wider use of testing and screening. However, many overdiagnosed cancer cases are incidental findings that is when the patient is being tested for something when the cancer is detected.

“Getting the balance right between too little and too much screening and testing will not be easy, but this is an important step.

It is the first time that the risk of overdiagnosis has been quantified across five cancers, anywhere in the world.” says Professor Glasziou.

“People still need to remain vigilant when it comes to early detection of cancers, however, they need to be informed and engage in shared decision making with their medical professionals about the harms of cancer screening and other associated procedures.”

Declaration: The researchers received funding from the Australian National Health and Medical Research Council.