Factors Associated with the Use of Gene Expression Profiles in Estrogen Receptor-Positive Early-Stage Breast Cancer Patients: A Nationwide Study

The Changing Role of Gene-Expression Profiling in the Era of De-escalating Adjuvant Chemotherapy in Early-Stage Breast Cancer

PURPOSE

We assessed the recent trends in the administration of adjuvant chemotherapy thereby evaluating the role of the 70-gene signature (70-GS) testing in decision-making in the systemic treatment of patients with lymph node negative (N0) and lymph node positive (N+) breast cancer.

METHODS

Patients with a national guideline directed indication for 70-GS use treated between 2013 and 2016 were selected from the Netherlands Cancer Registry. Time trends in the administration of adjuvant chemotherapy were evaluated within guideline- and age-delineated subgroups. The influence of the 70-GS on chemotherapy use was assessed with logistic regression.

RESULTS

During the study period, the overall administration of adjuvant chemotherapy decreased from 49 to 23% and 70-GS use increased from 24 to 51%. The 70-GS was not associated with a decreased likelihood for N0 patients to receive chemotherapy (odds ratio [OR] 1.0; 95% confidence interval [CI] 0.86-1.17), as the proportion of N0 patients who received chemotherapy in the absence of 70-GS use decreased during the study period. In patients with N1a disease, 70-GS testing was associated with a decreased likelihood to receive chemotherapy (OR 0.21; 95% CI 0.15-0.29). In patients < 50 years and 50-59 years of age, 70-GS use was associated with a consistent lower proportion of patients receiving chemotherapy throughout the study period (OR 0.17; 95% CI 0.13-0.23 and OR 0.53; 95% CI 0.43-0.65, respectively).

CONCLUSIONS

In this population-based study, the administration of adjuvant chemotherapy in ER+ breast cancer strongly declined. For node-positive and younger patients, 70-GS use was associated with a decreased probability for patients to receive adjuvant chemotherapy.

Use and Impact of the 21-Gene Recurrence Score in Relation to the Clinical Risk of Developing Metastases in Early Breast Cancer Patients in the Netherlands

BACKGROUND

The nationwide use of the 21-gene recurrence score (21-RS) and implications regarding chemotherapy administration in relation to clinical risk in early breast cancer patients are investigated.

METHODS

Breast cancer patients surgically treated between 2014 and 2016 were selected from the Netherlands Cancer Registry and categorized as having a clinical low, intermediate, or high risk of developing metastases. Deployment of the 21-RS is advocated in patients with an intermediate risk of developing metastases. The use and impact of the 21-RS test result on chemotherapy administration were assessed in relation to the clinical risk as well as patient and tumor characteristics; χ2 tests were used for analysis.

RESULTS

Of all patients, 20,488 were considered as clinical low-, 4,309 as intermediate-, and 15,266 as high-risk patients. The 21-RS was deployed in 0.1% (n = 23), 3.2% (n = 137), and 0.6% (n = 90) of these categories, respectively. In the clinical intermediate-risk group, the 21-RS assigned 73.7, 13.1, and 13.1% of patients to the genomic low-, intermediate-, and high-risk category, respectively. Adherence to the 21-RS was 95.6% in these patients.

CONCLUSION

In the Netherlands, the 21-RS test is applied both inside and outside the guideline-directed area. In case of discordance between the genomic and clinical risk, patients were treated in line with the result of the 21-RS.

Impact of gene-expression profiling in patients with early breast cancer when applied outside the guideline directed indication area

PURPOSE

In Dutch guidelines, gene expression profiles (GEP) are indicated in estrogen receptor positive early breast cancer patients in whom benefit of chemotherapy (CT) is uncertain based on traditional prognostic factors alone. Aim of the present study is to assess the use and impact of GEP on administration of adjuvant CT in breast cancer patients who have according to national guidelines a clear indication to either use or withhold adjuvant chemotherapy (clinical high or low risk).

METHODS

Clinical low- and high-risk patients, according to Dutch breast cancer guidelines, diagnosed between 2011 and 2014 were selected from the Netherlands Cancer Registry. Influence of GEP use and GEP test result on CT administration was assessed with logistic regression.

RESULTS

Overall, 26,425 patients were identified; 4.8% of patients with clinical low risk (444/9354), 7.5% of the patients with a clinical high risk (1281/17,071) received a GEP. GEP use was associated with significantly increased odds of CT administration in clinical low-risk patients (OR = 2.12 95% CI: 1.44-3.11). In clinical high-risk patients, GEP use was associated with a decreased frequency of CT administration (OR = 0.55, 95% CI: 0.48-0.63). Adherence to the GEP result was higher in clinical high-risk patients with a discordant GEP result as compared to clinical low-risk patients with a discordant GEP result: 71.7% vs. 52.2%, respectively.

CONCLUSION

GEP is frequently used outside the indicated area and significantly influenced the administration of adjuvant CT, although adherence to the test result was limited.