E78: Use of Genomic Testing for Locally Recurrent Estrogen Receptor-Positive Breast Cancer

ePoster Abstract Author(s)

Mary M. Mrdutt, MD, MS

Assistant Professor of Surgery
Division of Breast and Melanoma Surgical Oncology, Department of Surgery, Mayo Clinic, Rochester, MN, USA
Rochester, Minnesota, United States

Submitter(s)

Mary M. Mrdutt, MD, MS

Assistant Professor of Surgery
Division of Breast and Melanoma Surgical Oncology, Department of Surgery, Mayo Clinic, Rochester, MN, USA
Rochester, Minnesota, United States

Author(s)

Mary M. Mrdutt, MD, MS

Assistant Professor of Surgery
Division of Breast and Melanoma Surgical Oncology, Department of Surgery, Mayo Clinic, Rochester, MN, USA
Rochester, Minnesota, United States
CD

Courtney Day, MS

Instructor in Biostatistics
Mayo Clinic, United States
Tina J. Hieken, MD

Professor of Surgery
Mayo Clinic
Rochester, Minnesota, United States
Judy C. Boughey, MD (she/her/hers)

Chair, Division of Breast and Melanoma Surgical Oncology
Mayo Clinic
Rochester, Minnesota, United States
MG

Matthew P. Goetz, MD

Deputy Director of Translational Research, Professor of Oncology and Pharmacology
Mayo Clinic, United States
Amy C. Degnim, M.D.

Professor of Surgery
Mayo Clinic
Rochester, Minnesota, United States

Introduction: Multi-gene tumor testing is standardly used to select the optimal systemic therapy for patients with early-stage estrogen receptor-positive (ER+) primary breast cancer. However, while one clinical trial, CALOR, showed no benefit for adjuvant chemotherapy for ER+ locally recurrent breast cancer, multi-gene testing was not employed. Little data exists on the use and value of multi-gene testing for local recurrence (LR) and its role remains undefined. Thus, we evaluated one such test, the 21-gene Recurrence Score (RS), for ER+ LR.

Methods: With IRB approval, we identified 461 patients with ER+ LR breast cancer without distant metastasis treated surgically at our institution from 9/2008-9/2023. Patient demographics, tumor characteristics for primary and LR tumors including RS and treatment modalities were reviewed. To determine RS eligibility, guidelines for primary ER+ breast cancer testing were extrapolated to LR cases. RS use over time was evaluated with Cochran Armitage trend test. Associations between patient and tumor factors with RS use were assessed with Chi-square and Wilcoxon tests.

Results: Of 257 patients with ER+ LR eligible for RS, 58 LRs (22.6%) were tested; the proportion tested was stable over time (p=0.50). An additional 4 patients recommended for testing had no RS data due to patient refusal (n=2), insufficient sample (n=1), and non-RS multi-gene testing (n=1). Patients tested were younger (median 61.8 vs 68.8 years, p< 0.001) and although not statistically significant had a longer disease-free interval before LR [12.2 (IQR:6.9, 17.3) vs 8.6 (IQR: 3.8, 17.1) years, p = 0.07]. Frequency of RS testing also differed by pathologic nodal status, with pN0 66.0%, pN1 20.0%, pNx 14.0% among RS tested versus pN0 56.0%, pN1 9.9%, pNx 34.1% among RS not obtained (p = 0.010). Index surgery did not differ (mastectomy 13.8% vs 23.1%, p=0.13). 41 patients (17.0%) received chemotherapy. Patients whose tumors were tested for RS were twice as likely to receive chemotherapy [15/53 (28.3%) vs 26/188 (13.8%), p=0.013]. A RS ≥26 was more frequent in patients receiving chemotherapy versus those not (80.0% vs. 0.0%, p< 0.001), with RS distribution shown in Figure.

Conclusions:

Over 20% of patients at our institution with ER+ LR breast cancer underwent multigene tumor testing. Testing was associated with a two-fold higher rate of chemotherapy administration. Further studies are ongoing to evaluate the prognostic effects of LR-RS. Prospective clinical trials are warranted to evaluate the role of multi-gene tests to guide systemic therapy for patients with ER+ LR.

Learning Objectives:

describe use of multi-gene testing in estrogen positive primary versus locally recurrent breast cancer.
discuss the use of the 21-gene recurrence score and differences in chemotherapy administration for estrogen positive locally recurrence breast cancer.
list the potential benefit of multi-gene testing for estrogen positive locally recurrent breast cancer.