Forum: Balance benefits of breast cancer screening against potential harms

I refer to senior health correspondent Salma Khalik’s article on the overdiagnosis of breast cancer in women above 70 (Should older women go for breast cancer screening? Experts divided, Aug 26).

This is a timely reminder to the public that cancer screening may cause more harm than good in selected patient population. Potential harms of screening include:

1. False positive findings: This means abnormalities are found in the screening test, but eventually turn out to be non-significant. It is estimated that 10 per cent of all mammograms would lead to further evaluation, yet eventually, less than 10 per cent of these would be found to have breast cancer. This implies many patients would go for further testing after a mammogram, like magnetic resonance imaging or biopsy, for no good benefits.

2. False negative findings: This means the screening test fails to diagnose a real problem.

3. Overdiagnosis: This means the screening picks up a disease that would not have caused a problem or death. It is estimated that 10 per cent to 50 per cent of breast cancers are overdiagnosed. This is especially so in older people, where competing risks like cardiovascular diseases are prevalent. Making a diagnosis of early cancer in an elderly patient may not help prolong life, as she could die from other diseases like heart attacks or stroke, before the cancer exerts symptoms or problems.

4. Other harms: These include pain, cost, anxiety, and repeated exposure to radiation during mammograms.

While Dr Sim Yirong, senior breast surgeon at the Singapore General Hospital, sums up the benefits of breast cancer screening, these benefits must be balanced against the potential harms.

Professor Mikael Hartman, head of breast surgery at National University Hospital, made the best conclusion, that women above age 70 should discuss with their doctors the benefits and potential risks before getting screened.

Not all women would benefit from breast cancer screening.

Desmond Wai (Dr)