PPS32. Impact of genetic testing on surgical management in breast cancer: Results from a universal genetic testing program

Friday, March 6, 2026

3:40 PM - 4:10 PM MST

Location: HUB Poster Park - West Hall 1-3

Poster Presenter(s)

Victoria Hayman, MD (she/her/hers)

General Surgery Resident
McGill University
Montreal, Quebec, Canada

Co-Author(s)

ZR

Zoulikha Rezoug, MSc CCGC

Department of Biomedical Sciences, College of Health Sciences, QU Health, Qatar University
Doha, Ad Dawhah, Qatar
ST

Stephanie P. Totten, MD PhD

Department of Human Genetics, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
AA

Adrienne Atayan, MSc CCGC

Lady Davis Institute of the Jewish General Hospital, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
GC

George Chong, PhD

Department of Human Genetics, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
JB

Jean-Francois Boileau, MD MSc

Assistant Professor
Department of Surgery, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
Ipshita Prakash, MD MSc

Assistant Professor
Department of Surgery, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
MB

Mark Basik, MD

Associate Professor of Surgery and Oncology
Department of Surgery, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
Sarkis Meterissian, MD MSc (he/him/his)

Professor
Department of Surgery, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
FT

Francine Tremblay, MD

Department of Surgery, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
DF

David Fleiszer, MD MSc

Department of Surgery, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
DA

Dawn Anderson, MD

Department of Surgery, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
WF

William D. D. Foulkes, MBBS PhD

Director, Program in Cancer Genetics, McGill University
Department of Human Genetics, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada
Stephanie M. M. Wong, MD MPH

Assistant Professor
Department of Surgery, McGill University, Montreal, QC, Canada
Montreal, Quebec, Canada

Introduction

Inherited germline pathogenic variants (GPVs) are identified in 5-10% of breast cancer cases. The American Society of Breast Surgeons recommends universal genetic testing for breast cancer, but the impact of testing on surgical management remains understudied.

Methods

A retrospective chart review was performed for women who received a diagnosis of a first primary invasive breast cancer and underwent multigene testing as part of a multicentered, prospective universal genetic testing study between September 2019 and April 2022. Multivariable analysis was performed to identify factors associated with choice of surgical management, including breast conserving surgery, unilateral mastectomy, or bilateral mastectomy.

Results

Of 805 patients with breast cancer who were eligible and offered genetic testing, 729 (90.6%) underwent testing and 688 (94.4% of those tested) had operable breast cancer. The median age at breast cancer diagnosis was 53 years (range = 23-91 years), and 65.4% were White and of European ancestry. A total of 54 GPVs were identified in 53 (7.3%) of 729 patients tested. With respect to surgical management, 438 (63.7%) underwent breast conserving surgery, 171 (24.9%) underwent unilateral mastectomy, and 79 (11.5%) underwent bilateral mastectomy. In 36 carriers of BRCA1/2 or PALB2 GPVs who had operable breast cancer, 29 (80.6%) had a change in surgical management after undergoing genetic testing. In contrast, among 15 carriers of moderate penetrance GPVs including ATM, CHEK2, and others, only 1 (6.7%) altered surgical management. Bilateral mastectomy rates were 69.4% in BRCA1/2 and PALB2 carriers, 6.7% in moderate penetrance carriers, and 8.3% in non-carriers (p<0.001). On age-adjusted multivariable analysis, clinical factors independently associated with bilateral mastectomy included BRCA1/2 or PALB2 carrier status (odds ratio [OR] 27.3; 95% CI 10.5-70.6), bilateral breast cancer (OR 3.63; 95% CI 2.14-6.15), and invasive lobular/mixed carcinoma (OR 2.77; 95% CI 1.42-5.41). Moderate penetrance GPVs were not associated with increased bilateral mastectomy receipt (OR 0.58; 95% CI 0.07-5.15).

Conclusions

In women with invasive breast cancer, genetic testing at diagnosis was associated with a change in surgical management in over 80% of BRCA1/2 and PALB2 GPV carriers. High penetrance but not moderate penetrance GPVs were independently associated with increased bilateral mastectomy receipt.

Learning Objectives:

Participants should be able to recognize the association between genetic testing and a change in surgical management of breast cancer in women with high penetrance germline pathogenic variants.
Participants should be able to understand the association between high penetrance, but not moderate penetrance, germline pathogenic variants and increased bilateral mastectomy receipt.