A breast consists of glands and fat. Women with very dense breast tissue have a lot of glandular tissue and little fat in their breasts. Glands show up as white matter on an X-ray. Breast cancer also shows up as white. This makes it challenging to identify the breast cancer. The star in the four X-rays below shows this: in the rightmost X-ray, the star is more difficult to see. 

X-rays of the breasts (mammograms) are taken to determine the density. On a mammogram, fat is black and glandular tissue is white. At density D, there's a lot of white, which makes it hard to see tumours. There are four categories, going from not dense (category A) to very dense breast tissue (category D).

The National Programme for Breast Cancer Screening is for people between 50 and 75 years old. On average, 8 out of every 100 people in this group have very dense breast tissue. 

On an X-ray of the breasts, special software can measure whether someone has very dense breast tissue. An assessment of the density based on a breast X-ray is not reliable. People cannot feel it either.

At present, the density of the breast tissue is not measured by the mammogram in the National Programme for Breast Cancer Screening.

Having very dense breast tissue is partly hereditary. But this is not the only explanation. Other factors, such as age and hormones, also affect the density of breast tissue. As people get older , in most cases the density of their breast tissue decreases.

Yes, women between 50 and 75 years of age with very dense breast tissue have a higher risk of breast cancer than the 'average' Dutch woman in this age group.

See this page for more information on risk factors for breast cancer.

Currently, the density of the breast tissue is not measured by the population screening mammogram. From 2030, when MRI is added, this will happen. At that time, if you have very dense breast tissue and would like to know this, the information will be in your results letter.

If you are eligible for an additional MRI, you will then be referred.

Recently, a motion was passed in the Dutch House of Representatives to measure breast tissue density and link it back to mammogram participants even before 2030. This is currently being developed further.
 

Yes, you can request your X-rays. You can contact the population screening implementation organisation about this. 

If you are concerned about your breasts, you can make an appointment with your GP to discuss this. The GP cannot specifically   refer you for an MRI scan. That is a decision made by the breast cancer specialists in the hospital. The healthcare provider guideline states that at this time, dense breast tissue is not an indication for an MRI scan.

When referred, the radiologist will determine the best form of examination. This can  be an MRI scan or possibly an alternative form of examination.

With the regular population screening based on a mammogram, tumours are missed relatively more frequently in participants with very dense breast tissue. However, population screening is absolutely important to them as well. In participants with very dense breast tissue (density D), approximately 60% of tumours are detected, compared with 70-85% in women with lesser breast density. It is and remains important to participate in regular population screening.

Both studies are about a different way of examining breasts in women with very dense breast tissue, namely MRI. There is a difference between the MRI scan in the prior DENSE study and the MRI scan in the DENSE-2 study. In the first DENSE study, it took about 20 minutes to perform the MRI, while in the DENSE-2 study, it only takes about 5 minutes. We therefore call the MRI scan in the DENSE-2 study an abbreviated MRI scan. In the DENSE-2 study, we also investigate another technique, namely a contrast-enhanced mammogram.

The MRI offer must be available from 2030.

Currently, preparations are being made for the implementation of the density measurement and MRI option. This must meet high standards, and radiologists must be trained.

At present, scientific research is being conducted into alternative methods to improve breast cancer screening for women with very dense breast tissue. This is the DENSE 2 study.

It may be that results from this study show that MRI is not the best method. This will be known after the completion of the DENSE 2 study in 2031. A reassessment will then take place as to what is the best way to screen women with very dense breast tissue.

Until then, MRI will be offered to women with very dense breast tissue, and beyond that, there will continue to be an additional option for this group.

With the introduction of MRI in 2030, the mammogram will also measure breast tissue density. That is the breast cancer screening method already being used for women between 50 and 75 years of age. Because breast tissue density decreases with age, a mammogram is performed first.

• An MRI will only be offered to women with very dense breast tissue (density D).
• An MRI is offered every screening round.
• Due to healthcare capacity problems, the MRI expansion will be phased in. That means that not all women with dense breast tissue will be invited at the same time.
• The women will be informed clearly after decisions have been taken.

When breast cancer screening is expanded to include an MRI offer, breast tissue density is measured in each screening round. Because the density decreases with age, it must be measured each round. Participants with very dense breast tissue are referred for an MRI.

When the use of MRI is implemented, the exact guidelines for this will need to be established. It is important that women get an MRI as soon as possible after their mammogram if they have very dense breast tissue. This limits the uncertainty to a brief period. The waiting time also depends on the available MRI capacity. The RIVM report assumes that the MRI can be scheduled approximately 2 months after the mammogram.

It is important that women get an MRI as soon as possible after their mammogram if they have very dense breast tissue. This limits the uncertainty to a brief period. The waiting time also depends on the available MRI capacity. The RIVM report assumes that the MRI can be scheduled approximately 2 months after the mammogram.

Whether everyone with extremely dense breast tissue can be offered an additional MRI scan straight away will depend on the phased implementation model.

From 2030, the MRI will temporarily become a permanent part of the National Programme for Breast Cancer Screening. This means that the screening test is not subject to the excess, and is offered free of charge to women with very dense breast tissue.

The main problem is the availability of radiographers. Radiologists expect fewer problems if there is good training and organisation available. There seems to be enough capacity at the moment, but it is important that women are invited on the basis of what is possible. This avoids waiting lists and displacement of other care.

There have been many discussions about this. Hospitals and independent treatment centres indicate that they can usually expand their capacity. After the MRI has indicated a finding, women are referred to follow-up care. There are currently signs that a direct introduction could lead to the displacement of other care. The implementation involves careful work to reduce the risk of displacement. Staff shortages can be solved by additional training, the smart deployment of staff, and using faster MRI protocols.

It appears there is enough capacity for MRI scans. RIVM advises to regulate the influx of women on the basis of available capacity. In addition, the influx must be handled gradually, so that additional capacity can be arranged. This ensures there is room on the MRI schedule for everyone, including women who have a hereditary predisposition for breast cancer.

When MRI is to be offered to women with very dense breast tissue, it is important to ensure that there remains sufficient MRI capacity for women with a hereditary predisposition.

It appears there is enough capacity for MRI scans. RIVM advises to regulate the influx of women on the basis of available capacity. In addition, the influx must be handled gradually, so that additional capacity can be arranged. This ensures there is room on the MRI schedule for everyone, including women who have a hereditary predisposition for breast cancer.

When MRI becomes available in 2030 for women with very dense breast tissue, it is important to ensure that sufficient capacity remains for women with hereditary predisposition.

In that case, the participant will be referred for follow-up and treatment. The population screening will only pass on the invitation and the result.

RIVM recommends that MRI be implemented step-by-step. The capacity for MRI testing and follow-up care is limited and must be well distributed. Gradual implementation prevents other patients from receiving less care. This ensures that the capacity and quality can be closely monitored.
A rushed roll-out could cause problems for other groups, such as women with hereditary predisposition. The details will be documented in an implementation plan.

Scientific research has only been conducted on MRI for women with density D. This implementation assessment also looked only at the options to make MRI available for women with density D. About 5-8% of women have density D, and 33% have density C (almost 1 million women).

It is not known how many cancer diagnoses are missed in women with density C. The effect of MRI screening in women with density C is also unknown.