Blood test for early detection of breast cancer in high-risk patients

Women with a high risk of developing breast cancer can take part in adapted screening programs. However, interval cancer still appears in 3-17% of the cases and screening is often postponed during pregnancy and lactation. Therefore, the TESBREAST study aimed to develop a non-invasive method for the early detection of breast cancer in high-risk women using blood serum-based proteins. The first analysis identified a panel of six highly discriminating proteins that differ between cases and controls up to 1-2 years before diagnosis.

Women with breast cancer susceptibility genes, such as the BRCA1 mutation, or a family history of breast cancer, have an increased lifetime risk of developing breast cancer of up to 72%.  Because of this increased risk, they take part in adapted screening programs. However, there are downsides to the current way of screening: there is still interval cancer that appears in 3-17% of the cases, and screening is often postponed during pregnancy and lactation. More importantly, cancer is only detected when it is already present. Therefore, the goal is to develop a less invasive method that can predict tumour onset. This was the reason to initiate TESTBREAST in 2011, a study for the early detection of breast cancer in high-risk women using blood serum-based proteins. The first results of this study were presented at EBCC 2022.

Study design

The TESTBREAST study was designed to include 1,250 women between 25-75 years old across several hospitals in the Netherlands who had an indication for frequent screening due to high-risk of developing breast cancer, including familial or genetically enhanced risk. Patients with previous invasive breast cancer or other malignancies in the last ten years (with the exception of basal cell carcinoma) were excluded from the study. Of these 1,250 patients, 40 women were expected to develop breast cancer during the study period. Blood samples were collected 1-4 times (two times on average) per year during screening appointments and at the time of breast cancer diagnosis. Changes in protein levels were analysed through targeted mass spectrometry. Controls were matched to the cases according to the hospital where they were included, birth year and the time the samples were taken. Cluster analyses were done to indicate differences between and within protein levels in serum samples of individuals. Statistical analyses were performed using ANOVA to select distinctive proteins for early breast cancer detection.

Results

After ten years, 1,164 women from 9 centres in the Netherlands have been included in the study, and approximately 60 of them have developed breast cancer. Some women surpassed 20 study visits and over 3,000 serum samples have been acquired. In a nested case-control analysis, serum samples of three women who developed a breast malignancy (cases) were longitudinally compared to three high-risk women who did not get the disease (controls).  Five blood samples were obtained per patient (n=30 longitudinally acquired blood samples). In total, around 700 proteins were identified in the cluster analysis. Overall, 90% of them differ more among patients than within the same patient, indicating a greater interpatient than intrapatient variability in protein levels of the longitudinally acquired samples. This suggests that patients could serve as their own control during the screening, since changes from baseline levels could predict tumour onset.  Based on two methods, one based on universally (ab)normal protein levels and one based on individually (ab)normal protein levels, six distinctive proteins indicative of early breast cancer onset were selected (p<0.05). The levels of these proteins increase towards diagnosis in the patients (already 1-2 years before diagnosis), while their levels stay stable in the controls.

Conclusions

The first analysis of the TESTBREAST study showed strong clustering patterns within longitudinal intrapatient samples, demonstrating the importance of identifying small changes in protein levels for individuals over time. Additionally, a panel of six proteins for early breast cancer detection in high-risk women was established, which are highly discriminating between cases and controls and differ already 1-2 years before diagnosis. This protein panel will be validated in the complete TESTBREAST cohort, with the final goal of developing a blood test that can be used for the early detection of breast cancer in high-risk women.

Reference

Hagenaars S, et al. Detection of breast cancer in high-risk women based on longitudinal changes in serum-based proteins: the TESTBREAST study. Presented at EBCC 2022; Abstract PPT-051.