Abstract P4-07-41: Is axillary evaluation still necessary in DCIS?

Abstract Background Ductal carcinoma-in-situ (DCIS) is a growing health problem in the world. Before the advent of screening mammography, the incidence of DCIS was low, and patients presented with DCIS that had become clinically symptomatic. Upon this evidence, a strategy of aggressive surgical therapy like the approach with invasive cancer was adopted. The status of the regional lymph nodes is the most important prognostic factor and predictor of survival in breast cancer, but as DCIS is a malignant proliferation of the epithelial inside the breast duct and, therefore, does not have the capacity to generate metastasis. However, an upstaging after surgery is possible. The need for sentinel node biopsy (SNB) in patients with a preoperative biopsy diagnosis of DCIS is still controversial but is done in selected cases. Objectives Our main objective in this study was to evaluate the surgical approach in the axilla (SNB or axillary dissection – AD) of patients diagnosed with DCIS in a single institution and describe the surgical treatment (mastectomy or breast conservative surgery – BCS). In addition, we aimed to find the reasons that led our surgeons to choose one or the other treatment. Methods A retrospective analysis was made using the Pérola Byington Hospital’s database, from January 2011 to December 2019. During this period, 11,373 cases of breast cancer were treated int the institution and 812 (7.4%) were DCIS. Data was available and we could analyze 494 patients who underwent core biopsy or vacuum-guided biopsy guided by mammography or ultrasound and were diagnosed with DCIS and underwent surgical treatment at the Hospital. We grouped the patients into 3 age groups: under 40, 40-49, and 50 and over. In all groups, we had patients who underwent SNB using the patent blue technique or axillary dissection (AD) and were evaluated using the H&E method. We had also evaluated the type of surgery (BCS or mastectomy) in each age group. Results DCIS was diagnosed through mammographic alterations in 62% of all cases and nuclear grade 2 was the most common, with 47%, followed by grade 3 and 1, 46% and 4%, respectively. In 2% of cases the data was missing. Comedonecrosis was present in 78% of our specimens. The type of surgery (radical or BCS) was evaluated and BCS was made in 360 patients (72,87% of the cases), with the axillary approach being performed in 125 patients of these patients (50,20% of cases that went to axillary approach including 9 patients that were submitted to AD). In 27,1% the surgical approach was a radical surgery (total mastectomy or skin sparing mastectomy) and in this group 92,5% were submitted to axillary approach. There was a strong correlation in the type of surgery and axillary approach (p-value 0,000) In the group of patients younger than 40 years, 74% of patients (17 out of 23 in total) underwent an axillary approach regardless of the type of surgery (p-value 0.036) When evaluating the predetermined age groups, we saw that most of our patients were 50 years or more (69%), followed by patients between 40-49 years (26%) and 5% in patients under 40 years. In only 3% of cases (16 in 494) we reclassified the lesion as invasive carcinoma after the surgery. None of them had a lymph node involved by malignant cells after surgery and that’s include the cases reclassified as invasive carcinoma. Conclusion The results obtained in this analysis showing no axillary involvement will make us rethink the indications for the concomitant surgical approach of the breast and the axilla in cases with a diagnosis of DCIS to reduce the axillary surgical overtreatment. It was not our goal to compare the costs, mobility, and complications of the surgical treatment as the survival in these patients that can be addressed in another studies. Citation Format: Marcellus Ramos, Andre Mattar, Andressa Amorim, Felipe Cavagna, Mariana Passos, Raquel Fernandes, Jorge Shida, Luiz Henrique Gebrim. Is axillary evaluation still necessary in DCIS? [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-41.