Document Type

Service Learning/Capstone Experience

Graduation Date

5-2019

Degree Name

Master of Public Health

Department

Biostatistics

First Committee Member

Lynette Smith

Second Committee Member

Chi Lin

Third Committee Member

Stephanie Koraleski

Fourth Committee Member

Armando De Alba Rosales

Abstract

Introduction

Molecular subtypes of breast cancer (BC) are well-established prognostic markers in early-stage BC patients. The addition of radiation therapy (RT) to breast-conserving surgery has improved outcomes in this patient population, with conventional fractionation (CF) and hypofractionation (HF) regimens displaying comparable morbidity and mortality. However, most studies have not taken into account molecular subtype. Thus, it is still unknown if outcomes are similar between CF and HF for each molecular subtype. Herein, the effects of molecular subtype on the efficacy of CF and HF radiotherapy regimens for early-stage BC patients receiving adjuvant RT was investigated.

Methods

A retrospective review of stage I/II BC patients who received surgical intervention (breast conservation surgery or mastectomy) followed by RT at UNMC between 2010 and 2017 was conducted. Demographics, tumor characteristics, treatment data (course and dose of radiotherapy), and outcomes information (progression and survival) were collected. Cumulative incidence function and Kaplan-Meier testing were used to assess recurrence and survival, respectively. Variables were then further analyzed using univariate and multivariable COX proportional hazard models.

Results

In total, 311 patients met the inclusion criteria, including 211 CF and 100 HF patients. Patients undergoing HF were of lower stage and grade, but increased age. Rates of locoregional recurrence, distant recurrence, and survival were similar between cohorts. When stratifying based on molecular subtype, no differences in recurrences or survival were observed. On multivariable analysis, only stage was a significant predictor of distant failure and survival.

Conclusions

Although patient numbers were low, these findings suggest that HF and CF are equally efficacious in controlling locoregional recurrence in early stage BC patients. Thus, a hypofractionated regimen for radiation therapy should be considered an option regardless of molecular subtype in early stage BC following breast conserving surgery.

Available for download on Wednesday, April 28, 2021

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