Breast cancer is, like all cancers, something that should be caught as early as possible, and testing has proven to be a very good thing.
Although the rate of breast cancer rose throughout the 90s, the amount of death it caused over that time actually went slightly down, which some experts believe is due to increased adoption of testing procedures like the mammography.
(On an unrelated but interesting note, the amount of breast cancer went down for the first time in the early 2000s, which may be due to less use of hormone replacement therapy.)
Testing saves lives. Getting routinely tested for breast cancer could lower the risk of dying from it around 30% in women older than 50, and around 20% in women 40-50. But how often and at what ages should mammograms be done?
The tests, after all, are pretty non-specific. A significant majority of mammograms that require further testing via biopsy are false-positives, which has significant economic and personal impact. Imagine being told you might have cancer. It’s very scary.
That said, breast cancer testing is a far cry from situations like that with prostate cancer. The initial tests for prostate cancer are 10-15% positive in healthy people, require multiple biopsies, and perhaps lead to a over-diagnosis rate possibly higher than 50%.
The three main tests for detecting breast cancer are: mammography, MRI, and sonography. There is a lot of debate over which methods to use and when, and each method has its own variations and methods. This article looks only at digital versus film-screen mammography.
Digital mammography is an emerging and increasingly popular method of mammography, versus the film-screen mammography that, logically enough, uses film. Importantly, the digital tests are at least as effective as the film version, but may be better at detecting abnormalities in pre-menopausal women. This is because the digital method allows greater manipulation for contrast and brightness and can detect cancers in women with denser breasts. And younger women have denser breasts.
Additionally, digital mammography may be superior at detecting cancer early on in women who are BRCA mutants and at very high risk. Someone with a BRCA1/2 mutation, for instance, may have a lifetime risk of 21-65% of breast cancer, most happening before age 40. Detecting cancer in those women is so a very high priority.
Finally, digital mammography may use less radiation, and provide digital results that don’t take up space, can be read by multiple experts at the same time, and all the benefits of having something be digital versus a physical copy.
That said, digital testing is more expensive and requires more training. Some technicians may prefer being able to hold results and inspect them by hand. Other limitations of digital screening include the large file sizes – which may be an issue on less than ideal computers.
Also, there is the theoretical possibility that a certain type of abnormality in breast tissue, that of calcifications – where growing cells leave traces of calcium – might be not seeable on digital screens. This could happen if the abnormality is smaller than a pixel and so missed.
A major study, the Digital Mammographic Image Screening Trial (DMIST), looked at about 50,000 women who used either digital or screening mammography. It found no difference in terms of diagnostic accuracy, but that digital were better at finding cancer in younger women. That said, however, there was no difference between the two groups in terms of size or stage of breast cancer when it was detected.
Ultimately, the most important factor may continue to be the expertise of the person reading the test results.