Abstract P1-20-29: Mastectomy rates in a single Brazilian institution through the past 15 years: Are we following the global trend?
Authors: Cunha Thatyane EspósitoGallo , Dassie Thamyse FernandaSá , Lima Julianne MariaSilva , Mano Max Senna , Mori Lincon Jo , Hanna Samir Abdallah , Melo Sandro ViniciusMachado , Marta Gustavo Nader , Andrade Felipe EduardoMartins 
Published: March 2020

Abstract
Background: Recent medical literature reports that mastectomy rates are increasing in early breast cancer. The reasons for this have not yet been elucidated and appear to be complex and can be related to: availability of immediate reconstruction, expertise of the surgeon, increment of genetic tests and beliefs, unwillingness or impossibility of receipting radiotherapy, and information of the patients themselves. The present study aimed to demonstrate mastectomy rates throughout the years from a single Brazilian institution and to correlate it with age, neoadjuvant therapies and tumor staging.
Methods: A retrospective analysis of breast cancer surgeries from patients treated at Hospital Sírio-Libanês cancer center from 2005 to 2018 was performed. The institutional database electronically of physically registered in this period included pathology, radiology, and clinical information. Chi-squared coefficient of correlation was applied for categorical variables analysis of association, and for significant findings a multivariate regression analysis was performed. All statistical analyses were performed in STATA version 15.1C.
Results: Medical records from 2,942 patients treated were analyzed. 1,798 mastectomies (including nipple-sparing mastectomies and skin-sparing mastectomies) were performed against 1,144 conservative surgeries (61.11% x 38.89%). The range of mastectomy rates varied from 73.04% (2007) to 48.8% (2018) and mastectomy rates showed a slight decrease (53.84% in 2005 and 48.14% in 2018). Type of surgery (conservative, mastectomy, skin-sparing mastectomy) was associated with neoadjuvant treatment (p&lt;0.001). Multiple regression analysis found that radical surgery was inversely correlated to the date of surgery, having radical strategies fewer indications along with the time (R &lt; -0.001 ; t= -2.15 ; p=0.03), inversely correlated to age, being older aged patients more likely to underwent radical strategies (R= -0.004 ; t= -4.74 ; p&lt;0.001), directly correlated to advanced stages (R=0.13 ; t=10 ; p&lt;0.001). No significant linear correlation was found between type of surgery and neoadjuvant treatment when controlled for date, age and T staging.
Conclusions: These results demonstrate that our mastectomy rates, differently from global trends, did not increase through the past 15 years. These findings are probably related to impossibility of genetic tests in this population, accurate diagnostic techniques and the achievement of higher response rates with neoadjuvant treatment. Interestingly, breast-conserving surgery rates were inversely correlated with older age, which can reflect an individualized therapeutic approach among a subgroup of patients potentially vulnerable to chemo-related toxicity.
Citation Format: Thatyane EspósitoGallo Cunha, Thamyse FernandaSá Dassie, Julianne MariaSilva Lima, Max Senna Mano, Lincon Jo Mori, Samir Abdallah Hanna, Sandro ViniciusMachado Melo, Gustavo Nader Marta, Felipe EduardoMartins Andrade. Mastectomy rates in a single Brazilian institution through the past 15 years: Are we following the global trend? [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-20-29.