Breast-Conserving Surgery in Patients With Mammary Paget's Disease.

BACKGROUND: We aimed to analyze the association between Paget's disease (PD) and breast cancer (BC) subtypes and compare the effect of breast-conserving surgery (BCS) as a local treatment with mastectomy for PD.

MATERIALS AND METHODS: Data of patients with histologic type International Classification of Diseases-0-3 8540-8543 who were treated from 1973 to 2014 were retrieved from the Surveillance, Epidemiology, and End Results database of the National Cancer Institute. A chi-square test was used to identify differences in categorical data among different groups. Overall survival (OS) was analyzed using the Kaplan-Meier method, log-rank test, Cox proportional hazards models, sequential landmark analysis, and propensity score-matched analysis.

RESULTS: The study cohort included 5398 patients. Triple-negative BC accounted for the fewest patients with PD-only (1/22, 4.54%), Paget's disease-ductal carcinoma in situ (PD-DCIS) (3/48, 6.25%), and Paget's disease-invading ductal carcinoma (PD-IDC) (23/352, 6.53%). According to the results of the log-rank test and Cox analysis, the 10-year OS rates were similar for the BCS and mastectomy subgroups among patients with PD-DCIS or PD-IDC. Furthermore, there were no significant differences in survival benefits among the different surgeries after propensity score matching. Landmark analyses for OS of patients with PD-DCIS or PD-IDC surviving more than 1, 3, and 5 y showed no significant differences in survival. There were statistical differences in 10-year OS rates for patients with PD-DCIS or PD-IDC who underwent radiation therapy, or not, following BCS (both, P < 0.001).

CONCLUSIONS: For patients with PD-DCIS or PD-IDC, breast conservation therapy with lumpectomy and radiation is an effective local treatment strategy, compared with mastectomy.