2917 - Treatment Patterns and Outcomes in Metaplastic Breast Cancer: A Single-Institution Retrospective Study

03:00pm - 04:00pm PT

Hall F

Screen: 14

POSTER

Presenter(s)

Samar Khan, MD, MS, BS - Loyola University Medical Center, Maywood, IL

M. Bolouri¹, S. A. Khan¹, P. Tang¹, K. Gomez², J. Weiss¹, P. Bhakta¹, C. Reyna³, W. Small Jr², and T. Refaat²; ¹Loyola University Medical Center, Maywood, IL, ²Department of Radiation Oncology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, ³Crozer Health, Drexel Hill, PA

Purpose/Objective(s): Metaplastic breast cancer (MBC) is a rare, aggressive subtype with distinct biological behavior and limited treatment guidance. This study evaluates treatment patterns and outcomes to inform clinical decision-making.

Materials/Methods: This IRB-approved retrospective study analyzed women diagnosed with MBC treated at a single institution from 2000 to 2022. Patient demographics, tumor characteristics, treatment modalities, and outcomes were collected. Kaplan-Meier survival analysis estimated local control (LC), distant control (DC), disease-free survival (DFS), and overall survival (OS).

Results: Among 43 patients, the median age was 61 years. Most were White (75.5%) and postmenopausal (71.4%). Tumor size was <2cm in 27.5%, 2-5cm in 35.3%, and >5cm in 19.6%. Chemotherapy was given to 65.9% (17.1% neoadjuvant, 36.6% adjuvant, 12.2% both), radiation therapy to 58%, and mastectomy was performed in 60.4%, while 39.6% underwent lumpectomy. At 1-, 3-, and 5-years, LC rates were 85.5%, 75.9%, and 71.7%; DC rates were 80.7%, 72%, and 65%; DFS rates were 76.2%, 67.6%, and 60.6%; and OS rates were 88.1%, 74.6%, and 67.5%. LC was 81.1%, 69.9%, and 62.9% with chemotherapy versus 93.3%, 86.7%, and 86.7% without. Radiation therapy improved LC to 92%, 80.4%, and 72.4% versus 69.2%, 57.7%, and 57.7% without. DC at 1, 3, and 5 years was 69.8%, 60.8%, and 51.0% with chemotherapy versus 100%, 92.9%, and 92.9% without, and 92%, 81.5%, and 68.4% with radiation versus 53.8%, 44.9%, and 44.9% without. DFS was 66.7%, 57.4%, and 47.4% with chemotherapy versus 93.3%, 86.7%, and 86.7% without, and 88%, 76.9%, and 63.5% with radiation versus 46.2%, 38.5%, and 38.5% without. OS at 1, 3, and 5 years was 88.1%, 74.6%, and 67.5%. Among 26 mastectomy patients, 12 (46%) received adjuvant radiation, while 14 (54%) did not. Local recurrence was 25% with radiation and 36% without, while distant metastases were 33% and 50%, respectively. Among 17 lumpectomy patients, 13 (76%) received adjuvant radiation, while 4 (24%) did not. Local recurrence was 7.6% with radiation and 25% without, while distant metastases were 15% and 25%, respectively. DFS (p=0.0204) and OS (p=0.0202) were significantly improved with radiation therapy.

Conclusion: In this single-institution retrospective study, radiation therapy was associated with improved DFS and OS in patients with metaplastic breast cancer. Further research is needed to refine treatment strategies and explore molecular targets for personalized therapy.