Precision medicine in breast cancer radiotherapy

Purpose: To advance precision medicine in the field of breast cancer radiotherapy by identifying subgroups with such a favorable prognosis that they can be omitted postoperative radiotherapy.

We will conduct two projects with the aims of developing a radiotherapy omission model and of analyzing how checkpoint molecule expression influences the benefit from postoperative radiotherapy.Project organization: Axel Tullberg, PhD student, Erik Holmberg, statistician, and Per Karlsson, professor.Timeline: The projects will start during 2022 and the results will be published by 2024.Scientific methods: A radiotherapy omission signature will be trained using gene expression data from a population-based cohort from Västra Götalandsregionen (n= 650) where around 200 patients did not receive radiotherapy.

The model will then be validated in the randomized SweBCG91RT cohort (n= 1187) and subsequently also in the SweDCIS(n=1046) cohort.

In the second project, PD-1 and PD-L1 expression will be evaluated and the impact on prognosis and benefit from radiotherapy will be assessed in the randomized trial.

Any potential findings will be validated in the other cohorts.Importance: Radiotherapy represents a cornerstone in the treatment of breast cancer but predictive biomarkers capable of personalizing this treatment are severely lacking.

These unique cohorts provide opportunity to define novel biomarkers which can be used to predict the individual benefit from radiotherapy in breast cancer.