There is no definite consensus about what women should do if they are reported to have dense breast tissue. But they should consult their doctors to assess other risk factors, such as family history and previous breast biopsy results, before deciding whether supplemental imaging is necessary.
If there is a very high risk, such as having the BRCA-gene mutation, then a magnetic resonance imaging (MRI) scan needs to be done in addition to mammography, said Dr Jill Wong, a senior consultant at the division of oncologic imaging at the National Cancer Centre, Singapore.
If there is no family history or significant medical history, they may need only a physical examination, on top of mammography.
In the United States, some doctors advocate supplemental ultrasound scans. But these have several drawbacks - they tend to find a lot of abnormalities that are not cancer and lead to unnecessary biopsies, said Dr Wong.
Yet others do tomosynthesis, which creates a three-dimensional picture of the breast using X-rays.
Each extra modality adds cost and some add radiation exposure to the screening process, said Dr Wong. Many of these supplemental procedures will find additional abnormalities which may require biopsies that are often negative for cancer, she said.
Despite the lack of statistical evidence to routinely recommend additional ultrasonography or MRI scans, women with dense breasts or significant additional risk factors should be made aware of, and offered, additional options, said Dr Esther Chuwa, a consultant breast surgeon at Gleneagles Hospital.
But as far as cancer screening is concerned, mammography remains the best method.
It is the only test that has been proven to be useful for screening, said Dr Chan Ching Wan, a senior consultant at the division of surgical oncology (breast surgery) at the National University Cancer Institute, Singapore (NCIS).
It detects life-threatening disease at an earlier, more curable stage.
While 15 per cent of cancer cases are not detectable by this method, no other method has been shown to be better in terms of economy, efficiency as well as rates of detection, said Dr Chan. It is also fast. Reports can be out in two hours.
The recently developed three-dimensional imaging technique - tomosynthesis - can potentially improve the accuracy of mammography, by reducing overlapping shadows from breast tissue. Studies have shown that this technique decreases recall rates - when patients are asked to return for further tests due to an abnormal mammogram.
It is better at differentiating between worrying and benign lesions, without a decrease in the number of cancer cases found, said Dr Chan. NCIS will be getting this machine at the end of this year, she added.
Breast cancer is currently the most common cancer among women in Singapore, with more than 9,200 women diagnosed with the disease between 2010 and 2014.
Yet a recent study found that half of women here go for a mammogram only when they have symptoms. The study was carried out by doctors from Changi General Hospital's Breast Centre @ Changi on more than 1,000 women. The study also revealed that women here have poor knowledge about screening mammograms. They are unaware of the appropriate age to begin screening, despite having good general knowledge about the disease.
Ng Wan Ching