How quickly do breast cancers grow?

In these projects, data from BreastScreen Norway are used to develop statistical models that can increase our understanding of the development of breast tumors and women’s breast cancer survival.

Last updated: 11/12/2023

Background

Breast cancer is the most common cancer among women in Norway. However, much is still unknown about breast cancer tumours and their ability to grow and develop.

In BreastScreen Norway, asymptomatic women are screened for breast cancer every other year. Data from BreastScreen Norway can be used in statistical models to estimate the time period between when a breast tumor can be detected on screening mammograms and when the tumor is detected due to symptoms. This period is not directly observable, but is important to gain knowledge about in order to increase our understanding of how breast tumours grow and develop, and how the disease could have developed had the tumours not been detected by screening. This way we can also increase our understanding of overdiagnosis and overtreatment in breast cancer screening.

We also need more knowledge about breast cancer detection and so-called false positive screening examinations, which refers to when radiologists observe suspicious findings on the screening mammograms, but additional examinations do not detect cancer. Previous studies have shown that women with a false positive screening examination have increased risk of developing breast cancer later in life, and we thus need more studies to elucidate this correlation.

These types of studies will increase our knowledge about overdiagnosis and survival of breast cancer in BreastScreen Norway, and can also contribute as a scientific basis for more a personalized screening program where e.g., frequency of screening is more adapted to women’s individual risk of breast cancer.

The section for breast cancer screening at the Cancer Registry of Norway is currently project partner in two international research projects that aim to develop and use advanced statistical models utilizing data from BreastScreen Norway in order to increase our understanding of how breast tumors grow, develop and are detected, thus providing increased knowledge about overdiagnosis and survival of breast cancer among women participating in BreastScreen Norway.

Aim

The aim of the project is to enhance our understanding of how breast cancer develops, including why and how false positive screening results occur, and provide increased knowledge about overdiagnosis and survival of breast cancer. This will help improve BreastScreen Norway.

The projects will also help us gain knowledge about the possibilities of a more personalized screening program, meaning the screening service can be adapted to groups of women or individuals according to different parameters, like risk of breast cancer and screening history among others.

Project implementation

We will use screening information and information about breast cancer diagnoses from the Cancer Registry’s databases, in accordance with the Cancer Registry Regulation.

The study population is women aged 50 to 69 that have been screened in BreastScreen Norway and/or have been diagnosed with symptomatic breast cancer from 2006 and later. The projects will only use data from women who have not refused permanent storage of their personal information related to their screening examinations with normal results in the Cancer Registry of Norway.

The studies are registry-based and women will not be contacted about the project. It will not be possible to recognize individuals in the published results.

Organization

The Cancer Registry of Norway is the responsible research institution in both projects, and responsible for obtaining necessary ethical approvals in Norway, as well for the extraction, pseudonymization and transfer of data to external project partners. The Cancer Registry will contribute with analyses and interpretation of data.

The first project, "Estimation of the history of development and evolution of breast cancer from data collected as part of BreastScreen Norway", is a cooperation between the Cancer Registry and Università Commerciale 'Luigi Bocconi' in Italy. In this project, Università Commerciale 'Luigi Bocconi' is the institution responsible for the data in Italy, and responsible for obtaining necessary approvals there. They are also responsible for administering and analyzing the data in the project. The project is approved in the Regional Committee for Medical and Health Research Ethics (REK), project number 150166.

The second project, "Studying tumour progression and causes and consequences of false positive screening results in BreastScreen Norway", is a cooperation between the Cancer Registry and Karolinska Institutet in Sweden. In this project, Karolinska Institutet is the institution responsible for the data in Sweden, and responsible for obtaining necessary approvals there. They are also responsible for administering and analyzing the data in the project.

Status

Necessary agreements between the Cancer Registry and cooperating institutions are signed.

The dataset for the project in Italy has been delivered and made available to the project group trough the TSD (Tjenester for Sensitive Data) server. The project group in Italy are currently working on analyzing the data.

For the project in Sweden, the project group have applied for data from the Cancer Registry, and they will start working on data processing and analyses as soon as they have received the dataset.