Breast cancer screening does more good than harm, study suggests

[kkmalaysia]

The good that comes from breast cancer screening in terms of lives saved overrides the harms of overdiagnosis, according to a recent study.

Researchers reported that mammographic screening saves “between 2 and 2.5 lives” for every case that is overdiagnosed.

Although there is a majority view that screening for breast cancer outweighs the harms, the value of screening has recently been an issue of much debate, researchers noted.

Overdiagnosis refers to the detection of cancer through screening that would otherwise have not been detected within a woman’s lifetime, if the screening had not occurred.

It has been “claimed that the benefits in terms of lives saved are much smaller, and the harms in terms of overdiagnosis much larger, than had previously been thought,” wrote the study’s lead author, Professor Stephen W. Duffy, of the Cancer Research (CR)-UK Centre for Epidemiology, Statistics and Mathematics, at the Wolfson Institute for Preventative Medicine, Queen Mary University of London, UK, and his colleagues.

“Our estimates from both service screening and a major randomized trial show that there is a worthwhile benefit of mammography in terms of lives saved, and that this significantly exceeds any harm in the form of overdiagnosis that may occur,” the authors stated.

The findings come from the analysis of breast cancer incidence and death data from the Swedish Two-County study, a randomized trial of mammographic screening involving more than 100,000 women aged 40-74 and the UK National Breast Screening Program which was launched in 1988. [J Med Screen 2010;17:25-30 DOI:10.1258/jms.2009.009094]

“The absolute benefits were estimated as 8.8 and 5.7 breast cancer deaths prevented per 1,000 women screened for 20 years starting at age 50 from the Two-County Trial and screening program in England, respectively. The corresponding estimated numbers of cases overdiagnosed per 1,000 women screened for 20 years were, respectively, 4.3 and 2.3 per 1,000,” the investigators reported.

Dr. Marie Catherine Lee, an assistant professor of surgery in the division of oncologic sciences at the University of South Florida, US, and assistant member of the breast program at the H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, US, said that the study confirmed the belief and the findings of other studies that breast cancer screening continues to save lives.

“Quantifying overdiagnosis is very difficult. We would agree with the authors that the rate of overdiagnosis is small compared to the benefit that women gain by early detection and treatment of breast cancer. We strongly encourage all women of the appropriate age to have annual screening mammography,” said Lee.

Although mammography is not perfect, it is a good way to detect and treat breast cancer early, Lee added. “We know that early diagnosis translates to better survival.”

Dr. Georgette Chan, a general and breast surgeon at The Breast Surgery Centre, Paragon Medical Centre, Singapore, said that the findings of the study are reasonable because the Swedish Two-County Trial is a randomized study with an adequate follow-up, of 21.5 years.

“The estimation of absolute benefit is straightforward and derived from actual numbers from the trial, and hence is likely to be accurate. However, the estimation of overdiagnosis is from derived numbers rather than actual values, so those may not be as accurate,” Chan said.

Source: mims.com