How quickly do breast cancers grow?

This project will use data from BreastScreen Norway to develop statistical models that can contribute to an increased understanding of the development of breast cancer tumours and women's survival of breast cancer.
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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 this project, we aim to develop statistical models to improve our understanding of breast cancer tumors' natural growth and development.

BreastScreen Norway screens asymptomatic women for breast cancer every other year. In this project, we are interested in estimating how long it takes for a breast cancer tumour detected on screening images to cause symptoms. This time period cannot be observed in real life because women whose cancers are found at screening are offered treatment for their disease as soon as possible. We will therefore develop statistical models to estimate the period, using - among other things - information about tumour size at the time of diagnosis, both for breast cancers detected at screening and breast cancers detected due to symptoms.


The aim of the project is to develop statistical models that can contribute to an increased understanding of the development of breast cancer tumours and survival of the disease among those who participate in BreastScreen Norway.

We expect that the knowledge acquired through this project will help developing mammographic screening and BreastScreen Norway by increasing our understanding of overdiagnosis and survival of breast cancer.

Project organization

The project will use information about screening and breast cancer diagnoses from the Cancer Registry's databases, in accordance with the Cancer Registry Regulations.

The study population is women aged 50-69 who have been screened in BreastScreen Norway and/or diagnosed with symptomatic breast cancer in 2006 or later. We will only include data from women who have not refused their personal data related to negative screening results to be permanently stored at the Cancer Registry.

This is a register-based study and the women will not be contacted about the project. It will be impossible to recognize individuals in published results.

The project is a collaboration between the Cancer Registry of Norway and Università Commerciale 'Luigi Bocconi' in Italy. The Cancer Registry is the data controller in Norway, and responsible for securing ethical approvals in Norway, as well as extracting, pseudonymizing and transferring data to the project group in Italy. The Cancer Registry will also contribute with analyzes and data interpretation. Università Commerciale 'Luigi Bocconi' is the data controller in Italy, and responsible for obtaining the necessary approvals in their country. The project group in Italy is also responsible for data management and analysis.


As of January 2023, the necessary agreements between the Norwegian Cancer Registry and Università Commerciale 'Luigi Bocconi' have been signed. The data set has been made available to the project group. The project team in Italy is currently working on analyzing the data.