PERMS-0: Pilot project for personalized mammographic screening in Norway

Background

Population-based screening programs for breast cancer, such as BreastScreen Norway, target asymptomatic women with an average risk of breast cancer. In Norway, all women aged 50 to 69 are invited to have a screening mammogram every two years in BreastScreen Norway. In this target group, both women with lower and higher risk of developing breast cancer are included.

Although screening intervals and age groups in breast screening programs may vary between countries, women included in the same screening program follow the same screening scheme, regardless of their individual risk of developing the disease. However, this "one-size-fits-all" approach is increasingly discussed among professionals and scientists. Studies have shown that more personalized mammographic screening, where the screening scheme is based on the individual's risk of developing breast cancer, may increase benefits and reduce harms for the women.

Among factors discussed related to such risk-based screening programs, is mammographic density. A woman's mammograhic density can be determined from her mammograms and is - briefly explained - a description of the amount of fat, glandular and connective tissue in the breast. The risk of developing breast cancer increases with increasing mammographic density. Also, the sensitivity of mammography is lower for women with high mammographic density. In addition, tumors present on mammograms with the same light color as do dense glandular and connective tissue, which means tumors may be difficult to detect. The European Society of Breast Imaging (EUSOBI) therefore recommend offering women with high mammographic density an additional examination as part of a personalized screening scheme. However, to date, no screening programs in Europe have established such a scheme, in large due to lack of capacity. Only few studies have been conducted on the topic, and they all show that women participate to a low degree in the studies where they are offered an extra examination, 50% or fewer. This pilot study will study this for Norwegian women.

Another risk factor for breast cancer is false positive screening result. This term is used when a woman who is called back for further examinations due to suspicious findings on the screening mammograms, while further examinations show that she does not have breast cancer. Studies, including some from BreastScreen Norway, have shown that women with a false positive screening result have an increased risk of later being diagnosed with breast cancer, either between screening rounds (so-called interval cancer) or at a later screening examination. It is suggested that mammography performed more frequently than every other year may be beneficial for these women.

In spite of increasing evidence about the potential benefits of personalized breast cancer screening programs, few studies to date have examined the practical aspects of offering such a program. Also, there is little knowledge about how such an offer would be received by the target group.

Purpose

The overall purpose of the pilot project is to gain more knowledge about the practical aspects of offering a personalized screening scheme in BreastScreen Norway. This knowledge will be used in further planning for a future personalized screening program in Norway.

The main goal is to gain knowledge about what proportion of women with increased risk of breast cancer due to their mammographic density or false positive screening result, would actually use an offer of having an additional examination.

We will also examine other quality indicators related to participation in BreastScreen Norway, such as the proportion of women called back for additional examinations and the proportion of breast cancers detected.

Implementation

PERMS-0 is a prospective cohort study consisting of two sub-studies. The sub-studies will be conducted in collaboration with the breast centers at Akershus University Hospital (Ahus), Oslo University Hospital (OUS) and Vestre Viken Hospital. Results will be compared with historical data from BreastScreen Norway.

Sub-study A - mammographic density: Will be conducted at Ahus. Women who attend screening will have their mammographic density measured, and those found to have high mammographic density will be invited to receive an additional examination with tomosynthesis within three months after the original screening examination.

Sub-study B - false positive screening result: Will be conducted at Vestre Viken Hospital and OUS. Women who receive a false positive screening result after regular attendance in BreastScreen Norway will be invited to receive an additional examination with mammography one year after their original screening examination.

All study participants must signe an informed consent before participating in the study. The women who are included will be followed for two years, to include information from the subsequent screening round in the analyses.

Data

The pilot project will only use information about women who have not rejected having their personal information related to screening examinations with normal findings stored in the Cancer Registry of Norway, in accordance with the Cancer Registry Regulations.

In substudy A, the Cancer Registry will register and use information about the additional examinations. In addition, the study will use the information related to attendance and findings on mammograms, which is stored in the Cancer Registry when you participate in BreastScreen Norway. This includes information about the radiologists' assessments, including results of the screening examinations (screening information). Information about the measurements of mammographic density at the screening appointment will also be used.

In substudy B, the Cancer Registry will register and use information about the additional examinations that are performed, and screening information from the current and previous appointments in BreastScreen Norway.

It will be impossible to recognize individuals in published results .

Organization 

The Cancer Registry of Norway at the Norwegian Institute of Public Health (NIPH) is the coordinating institution and data controller in the study. This includes responsibility for obtaining necessary approvals, collecting data, monitoring the study, quality assurance and analysis of data, as well as publication and reporting of results.

Both the Cancer Registry of Norway and the collaborating health trusts are responsible research institutions according to the Health Research Act. The parties have an independent responsibility for organizing and implementing the part of the study that is carried out at their own institution, and for ensuring that this is done in accordance with relevant regulations and formal approvals.

Status

The Cancer Registry of Norway is currently working to obtain the necessary approvals and prepare for the pilot project's start-up, including installation of necessary equipment, software and IT systems. The pilot project is scheduled to start in 2025.