John Byun, MD
Cancer Institute of New Jersey
PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s): The role of postmastectomy radiation (PMRT) in patients presenting with node positive breast cancer who receive neoadjuvant chemotherapy (NAC) and are pathologically node negative is an area of active investigation. With limited available data to guide management, we sought to examine patterns of PMRT and overall survival (OS) in this population using the National Cancer Data Base.
Materials/Methods: We included patients with invasive, non-metastatic, clinical T1-4 node positive breast cancer diagnosed between 2004 and 2013 who received NAC and underwent mastectomy with pathologically negative lymph nodes. Multivariate logistic regression was used to identify predictors of PMRT utilization. Five year OS was estimated using the Kaplan-Meier method, and factors associated with mortality were identified using Cox proportional hazards models.
Results: We identified 8,766 patients who met the study criteria, of whom 61.5% received PMRT. Median age was 49, and median follow-up was 39 months. Clinical N stage prior to NAC was cN1 in 78.2%, cN2 in 13.4% and cN3 in 8.5%. Presenting clinical T stage was T1-2 in 53.4% of patients and T3-4 in 46.6%, while pathologic T stage was T0-2 in 92.5% of patients, demonstrating significant down-staging with NAC. The rate of PMRT receipt by year ranged from 54.1% in 2004 to 65.1% in 2011 (median 62.5%). Predictors of PMRT use included younger age (≤50 vs. >50 years), lower Charlson-Deyo comorbidity score (0-1 vs. 2), non-Medicaid/Medicare insurance, closer distance from the treatment facility (≤50 vs. >50 miles), receipt of hormone therapy, clinical N2 or N3 disease (vs. cN1), clinical T3-4 disease (vs. cT1-2), greater number of LNs examined (≥10 vs. <10), higher grade disease, and absence of an immediate breast reconstruction. Race, income, facility type (academic vs. non-academic), pathologic T stage, and laterality were not significant associated with PMRT receipt. Although unadjusted 5-year OS was higher among patients who received PMRT (85.4% vs. 83.7%, p=0.04), adjusting for demographic and clinicopathologic covariates with multivariable analysis demonstrated PMRT was not associated with improved survival (hazard ratio [HR] 0.88, 95% CI 0.75-1.04). Predictors of mortality on multivariable analysis included older age, Medicaid/Medicare insurance, absence of hormonal therapy, clinical T3-4 disease (vs. T1-2), pathologic T1-2 or T3-4 disease (vs. pT0-Tis), and clinical N2 or N3 disease (vs. cN1).
Conclusion: About 60% of patients with clinically node positive breast cancer who were pathologically node negative after NAC and mastectomy received PMRT. Multiple socioeconomic and clinical predictors of PMRT receipt and survival were identified. Ongoing randomized studies may further elucidate the role of PMRT in this population.
Cancer Institute of New Jersey
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