23 Jun 2018

We refer to Ms Lilian Thia's letter (Relook benefits, harm of mammogram screening; June 15).

Mammography is not perfect, but it remains the most effective tool for population-based screening. Its benefits are supported by evidence from large-scale trials showing about 30 per cent reduction in mortality rate. With early detection, breast cancer therapy is also less radical, toxic and costly.

Radiation from mammograms is low and the risk of inducing cancers is negligible relative to the population risk of breast cancer. Some women may be asked to undergo a more complete medical examination after the initial screening and this is usually quickly resolved by further imaging.

Only 1 per cent to 2 per cent of screenings require minimally invasive biopsies. While the medical examination may cause inconvenience and anxiety, the benefit of finding early breast cancers significantly offsets the drawbacks.

Ms Thia mentioned that her friends diagnosed with ductal carcinoma in situ (DCIS) were given radiotherapy, chemotherapy and mastectomy.

DCIS, a pre-invasive cancer, is not treated with chemotherapy. When DCIS is discovered and managed before it progresses to invasive disease, chemotherapy and its side effects are avoided and the prognosis is excellent.

Ms Thia cited a 2015 Breast Cancer Research journal article which reported significant overdiagnosis and no reduction in the invasive breast cancer incidence after DCIS detection and treatment.

The article referred to scientifically unsupported estimates. In contrast, there is data showing prevention of invasive disease, and most experts do not think there is significant overdiagnosis of invasive cancers.

Importantly, mammogram screening reduces late-stage breast cancers.

In Singapore, where screening participation rate is low, women still present with advanced cancers, rendering poorer prognosis.

We agree that more can be communicated about the advantages and limitations of mammogram screening to clarify misconceptions, allay anxiety and help women make informed decisions.

The Swiss Medical Board looked at sub-optimal studies to arrive at its recommendation to stop mammogram screening. In contrast, major medical professional bodies around the world overwhelmingly favour mammogram screening.

We stand by the Ministry of Health's guidelines that women aged 50 to 69 years old be encouraged to have regular two-yearly mammograms.

Dr Lester Leong 

Chairman, Chapter of Diagnostic Radiologists
College of Radiologists, Singapore

Dr Andrew Tan

President, Singapore Radiological Society

Dr Choo Su Pin

President, Singapore Society of Oncology

Professor Tan Puay Hoon 

Fellow, Chapter of Pathologists
Academy of Medicine, Singapore

This letter can be viewed here and on The Straits Times Forum.