V18: Temporal Trends and Factors Associated with Receipt of Post-mastectomy Radiation (PMRT) After Neoadjuvant Chemotherapy (NACT) in Women with ct3 Breast Cancer

Tuesday, March 1, 2022

5:55 PM – 5:58 PM CST

Location: Zoom Meeting

Virtual Poster Presenter(s)

Ritika Manik

Research Specialist
University of Pennsylvania
Philadelphia, Pennsylvania, United States

Disclosure: Disclosure information not submitted.

Participants should be aware of the following financial/non-financial relationships:

Ritika Manik: Disclosure information not submitted.

Introduction: T3 disease is an indication for PMRT, but patterns of PMRT administration remain unclear for women with cT3 disease who present with absent or limited nodal disease and receive NACT followed by mastectomy. We sought to evaluate temporal trends in post-NACT PMRT, estimate the relationship between response to NACT and receipt of PMRT, and identify variation in overall survival (OS) in this population.

Methods: We identified women≥18 years old in the National Cancer Database diagnosed 2004-2016 with cT3N0-1M0 breast cancer treated with NACT and mastectomy. Case-mix adjusted logistic regression and Cox proportional hazards models were used to estimate the association between NACT response and PMRT receipt and between PMRT and OS, respectively. NACT pathologic responses were categorized as complete response (CR), partial response (PR), no response, or disease progression.

Results:

We identified 16,854 women (Asian/Pacific Islander=696, Black=2808, Hispanic=1454, White=11,136; median f/u=41 months). Among cN0 patients with CR or PR, PMRT rates declined over time from 71% for each group in 2005 to 37% and 50%, respectively, in 2016. CR and PR in cN0 patients were associated with decreased odds of PMRT receipt and improved OS (Table, p< 0.001); disease progression was associated with increased odds of PMRT receipt (Table, p< 0.001) but was not associated with OS. Among cN1 patients, PMRT rates decreased from 88% to 71% for CR, increased from 70% to 80% for PR, and increased from 71% to 83% for disease progression from 2005 to 2016. CR and PR in cN1 patients were associated with improved OS while disease progression was associated with worse OS (Table, all p< 0.01), but there was no association between NACT response and odds of PMRT receipt for cN1 patients. PMRT was not associated with OS in either cN0 or cN1 patients regardless of NACT response.

Conclusions: Our findings suggest that for cT3N0 patients, NACT response significantly influences decision-making for PMRT, but PMRT recommendations for cT3N1 patients remain inconsistent as we await the results of ongoing clinical trials (e.g., Alliance 11202).

Learning Objectives:

Describe trends in post-mastectomy radiation (PMRT) administration for cT3N0 and cT3N1 patients who have received neoadjuvant chemotherapy (NACT).
Describe the association between NACT response and survival for cT3N0 and cT3N1 PMRT and NACT recipients.
Describe the association between PMRT and survival for cT3N0 and cT3N1 PMRT and NACT recipients.