THE GREAT DEBATES
Breast cancer screening has been a source of controversy for decades, with some medical experts and patients questioning whether the benefits of mammography outweigh the risks. Currently, most women use mammography as their main form of routine screening, while other methods like magnetic resonance imaging ( MRI) are typically conducted only for further evaluation, or in conjunction with mammography, particularly for those women at high risk. Though most major health organisations have concluded that mammography is a valuable screening tool, others maintain that MRI is more effective and should be primarily conducted even for those women with an average risk of developing breast cancer.
What’s more, there’s also controversy over the age at which women should start screening for breast cancer – the main reason being that younger women have denser breasts, which makes it difficult to interpret mammograms in women below 50, or below menopausal age. After menopause, the breast’s glandular tissue is replaced by fatty tissue, making mammographic interpretations more accurate. As a result, mammography isn’t generally considered an effective technique for younger women.
The age issue aside, women with denser breasts are usually encouraged to undergo MRI or ultrasound screenings, as mammograms don’t always pick up cancers hidden by the dense tissue, producing false negatives – when findings appear normal even though breast cancer is present, creating a false sense of security and a possible delay in cancer diagnosis. So, while it’s true that MRI has been shown to rule out the presence of cancer to a high degree of certainty, making it an excellent tool for screening – particularly for patients at high genetic risk or those with dense tissue – many experts point out that MRI can miss some cancers that would otherwise be detected by mammography.
And, while MRI is considered to be more sensitive, mammography is considered to be more specific. Breast surgeon DR GEORGETTE CHAN, for instance, recommends MRI scans only in combination with mammograms for certain groups of patients, including young women with dense breasts, those with a strong family history of breast cancer and those with breast implants. Mammography, she says, has an accuracy rate as high as 90 to 95 percent, and has proven effective in detecting cancers early; early discovery is associated with a 20 percent drop in breast cancer mortality.
According to Dr Chan, recent advances in the field of mammography make the screening process even more effective. One example is 3D mammography (tomosynthesis), which is an extension of a digital mammogram. “The breast is compressed once and the machine takes many low-dose x-rays as it moves over the breast,” she explains. “Then, the images are combined to give a three-dimensional picture. This method uses more radiation than the standard two-view mammogram, but it may see problem areas more clearly and may possibly find more cancers.”
Radiation is, of course, a key factor in the cancer screening debate. Like normal x-rays, mammography uses ionising radiation to create images that are then analysed for any abnormalities. According to USbased cancer organisation Susan G. Komen, while the radiation exposure during mammography can increase the risk of breast cancer over time, this increase in risk is very small, with studies showing that the benefits of mammography overshadow the possible dangers from radiation exposure, particularly for women 50 and older. Dr Chan agrees, saying, “The amount of radiation is very low dose, akin to that of a couple of chest x-rays and much lower than a PET scan or a CT scan. So, the risk of harm is low, especially if done only yearly (from 40 to 50), and then every two years (from 50 onwards), as we recommend.” Nevertheless, the concern over exposure to small doses remains, and it’s up to the individual to make that choice for herself.
There’s also the issue of false positives – when findings indicate cancer when no cancer is actually present. Some medical experts and patients feel that, when taking into account the frequency of false positives in mammography and the potential for causing unnecessary distress, the risks of mammography offset the benefits. This is because many women who receive false positive results become anxious and fearful about the possibility of having breast cancer, and must return for anxiety- inducing follow- ups and testing, and unnecessary biopsies. On the other hand, it can be argued that this potential distress may be outweighed by the possibility of detecting cancer in its early stages.
MRIS can present false positives, too. In fact, Dr Chan says that MRI scans create more false positive results than mammograms do, because the scans are more detailed. “There’s a lot of overlap between normal and abnormal tissue. Even the timing of the scan in relation to the menstrual cycle can make a difference because of the hormonal influence.”
Comfort is another consideration that’s central to women’s screening decisions. Many women forgo an MRI based on the claustrophobic sensation, and the length of time the procedure takes. According to Dr Chan, while MRI scans are not painful since breasts are not compressed, the discomfort comes with having to lie on one’s belly for 45 minutes in a confined space. She also notes that MRI requires an intravenous injection of a dye via IV for better visualisation, making it more of an invasive procedure. On the other hand, some feel that MRI is less uncomfortable than mammography – it really depends on the individual’s comfort level.