Development and validation of a prediction model for identifying men with intermediate- or high-risk prostate cancer for whom bone imaging is unnecessary: a nation-wide population-based study

Abstract

Objective: To develop and validate a nomogram that identifies men for whom bone scan is unnecessary.

Material and methods: The study datasets were derived from the National Prostate Cancer Register (NPCR) of Sweden. All men in the NPCR ≤80 years of age who were diagnosed with intermediate- or high-risk prostate cancer and who had pretreatment bone imaging (^99mTc MDP scintigraphy, plain x-ray, computed tomography, magnetic resonance imaging, and/or positron emission tomography fused with computed tomography) were included. Men diagnosed from 2015–2016 formed a development dataset and men diagnosed in 2017 formed a validation dataset. Outcome was metastasis on bone imaging as registered in NPCR. Multivariable logistic regression was used to develop a nomogram.

Results: In the development dataset 482/5084 men (10%) had bone metastasis, the corresponding percentage in the validation dataset was 282/2554 (11%). Gleason grade group, clinical T stage, and prostate-specific antigen were included in the final model. Discrimination and calibration were satisfactory in both the development (AUC 0.80, 95% CI 0.78–0.82) and validation dataset (AUC 0.80, 95% CI, 0.77–0.82). Compared with using the EAU guidelines’ recommendation for selecting men for imaging, using the nomogram with a cut-off at 4% chance of bone metastasis, would have avoided imaging in 519/2068 men (25%) and miss bone metastasis in 10/519 (2%) men in the validation dataset.

Conclusion: By use of our nomogram, bone scans of men with prostate cancer can be avoided in a large proportion of men.

Keywords:

• Bone metastasis
• imaging
• prostate cancer
• staging

Acknowledgements

This project was made possible by the continuous work of the National Prostate Cancer Register of Sweden (NPCR) steering group: Pär Stattin (chairman), Anders Widmark, Camilla Thellenberg, Ove Andrén, Eva Johansson, Ann-Sofi Fransson, Magnus Törnblom, Stefan Carlsson, Marie Hjälm Eriksson, David Robinson, Mats Andén, Johan Stranne, Jonas Hugosson, Ingela Franck Lissbrant, Maria Nyberg, Göran Ahlgren, René Blom, Calle Walller, Per Fransson, Fredrik Sandin, and Karin Hellström.

Disclosure statement

Rebecka Arnsrud Godtman reports lecture fees from IPSEN. Marianne Månsson, Ola Bratt, David Robinsson, Eva Johansson, Pär Stattin, and Henrik Kjölhede have nothing to disclose.

Additional information

Funding

Grants have been received from the Swedish State under the agreement between the Swedish government and the county councils (the ALF-agreement) and the Department of Research and Development, Region Kronoberg.