The problem of screening younger women for breast cancer is an important health issue.

All too frequently we see women between 30 and 50 years of age presenting with a palpable clinical lump which turns out to be cancer and often at a rather late stage. Furthermore, when compared to the older more typical age group, young women with breast cancer usually have more aggressive high-grade disease. Frequently, even if a mammogram has been performed, nothing has shown up, often because the cancer cannot be distinguished from the normal dense breast tissue which most young women naturally have in preparation for lactation.

As women get older the breasts tend to involute and become more fatty, so mammography then does a much better job – hence the national screening program is aimed at women over 50 years. That said, though, a proportion of women have significant density persisting even beyond menopause.

Mammography, which uses X-rays, is something we try to avoid in younger women because radiation can actually cause cells to undergo malignant change. Guidelines generally recommend avoiding mammography at least until the mid-30s and there is still debate about whether routine screening mammography is worthwhile in the 40-to-50 age group.

The inconvenient truth here is that the sensitivity (detection rate) of X-ray mammography falls to well under 50 per cent in the densest breasts, so only half the cancers that may be present are likely to be detected.

The issue is topical at the moment as several US states have recently legislated that radiologists must tell women if they have dense tissue and explain that as a result mammography will be less effective.

Interestingly this all came about from the efforts of a young woman who was diagnosed with breast cancer and, quite reasonably, wanted to understand why it had not been seen on her recent mammogram. This case is having repercussions in Australia as radiologists are reconsidering the way they approach breast density as well.

So, what are the options? We always encourage women to become breast aware so they get to know what is normal for them. If anything seems different, particularly a new painless lump, women should see their GP for a check and usually have a breast ultrasound. This is a very good test, which can reliably exclude cancer as a cause of a palpable lump, although sometimes aspiration of a cyst or a biopsy may be needed.

As far as screening goes – meaning performing a test when there are no symptoms – the only options are really regular a ultrasound and an MRI (magnetic resonance imaging). Ultrasound screening will find some additional cancers not seen by mammography, but it also tends to find abnormalities which are not cancers – the false-positive result. This is inevitable with any screening procedure, but published ultrasound screening studies show that about 90 per cent of biopsies generated are negative. The false-positive biopsy rate is generally much lower in MRI screening.

To my mind, it is what we call the NPV, the negative predictive value, of breast MRI which is the most valuable in giving reassurance. When a good-quality, well-performed and competently reported MRI returns a normal result, the risk of breast cancer being diagnosed in the next 12 months (an interval cancer) is less than 1 per cent; and we cannot say that for any other breast imaging test.

The downsides of MRI? Cost, of course, is the main one, although Canberra is relatively affordable, with breast MRI available for about $500.

The availability of MRI is an issue, but many more scanners around Australia do now offer breast MRI. However, the level of experience of the technologists and the radiologists involved in the interpretation are other important factors in getting good results.

For whom do we recommend regular MRI? Since 2009, annual breast MRI has been covered by a Medicare rebate for women at the highest risk based on family history, but only up to age 50 years of age and if they are referred by a medical specialist. Typically this would be a young woman who has at least two first or second-degree relatives with breast cancer, at least one of whom had been diagnosed under the age of 40.

Ovarian cancer, bilateral breast cancer and male breast cancer are other important factors in the family history. For these there is now very good evidence that MRI allows much earlier detection. But even if a woman has just one affected first-degree relative, say mother or sister with breast cancer before age 50, they have about double the average risk – so they have a 20 per cent lifetime risk of breast cancer. If they then have significant breast density, this adds to the risk and reduces the sensitivity of mammography.

There is a lot of argument as to who should be screened with MRI and even exactly what constitutes high risk.

A group I would recommend for a regular MRI would be younger women already diagnosed with breast cancer – mainly to check the other breast, which is at substantially increased risk in the future.

We have been monitoring our performance with MRI screening closely since 2005 and have found many cancers by MRI in women who are not in the familial high-risk category – usually they have either a personal history of breast cancer at a young age or have one affected relative – but have significant breast density.

High-profile celebrity breast cancer diagnoses have heightened awareness. Take the recent case of Angelina Jolie, who underwent a double mastectomy because she carried the BRCA1 gene. Women who have a BRCA1 mutation are an important subgroup as they tend to get a particularly aggressive subtype of cancer. In these women it is possible for a cancer to develop between annual MRI screens and even become quite large. In such cases there may also be unseen systemic spread of disease at a relatively early stage. Women with the relatively common BRCA2 gene are much less of worry in that regard – their cancers generally obey the usual rules.

Women at extreme risk should always keep in mind though that increased surveillance does not prevent cancer – it just aims for earlier detection. I have seen instances where most of a breast is involved with cancer and yet nothing had been detected by mammogram or ultrasound. The point is that early diagnosis means more chance of achieving breast conservation with a good cosmetic result and better survival outcomes.

Women need to be aware that if they have breast density they need to be a bit more vigilant and should consider adding ultrasound or MRI to their surveillance program. While mammography is still a very useful test, it has limitations, and having had a recent mammogram does not definitively exclude cancer. So, any change in the breasts, particularly a painless lump, requires a timely trip to the GP.

Dr Jeremy Price is a Canberra radiologist with a special interest in breast imaging and has been performing breast MRI scans since 1995.

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