Abstract P5-17-05: Local recurrence rates after mastectomy undertaken for pure ductal carcinoma in situ (2016)

Abstract Currently over 30% of patients with ductal carcinoma in situ (DCIS) are treated by mastectomy. Local recurrence rates (LRR) after simple mastectomy for DCIS have historically been reported as low1. Recent UK and US data has indicated 5-year local recurrence rates after mastectomy for DCIS are increasing2. Skin sparing mastectomy (SSM) offers a better cosmetic outcome however there is little work in the literature comparing local recurrence rates between simple and SSM for pure DCIS. Local recurrence rates may be higher after SSM compared to simple mastectomy3. Aims: 1. To evaluate what local recurrence rates were after mastectomy performed for pure DCIS. 2. To compare LRR in simple against SSM. Methods: We undertook a retrospective analysis of all patients who underwent a mastectomy for pure DCIS at one breast unit between 2000-2010. Operation reports were reviewed and data collected on the type of mastectomy and reconstruction used. Pathology reports were reviewed and the histological type, grade, size of DCIS as well as the presence of micro-invasion, excision margin and molecular phenotype were recorded. We excluded those patients who were having surgery for recurrent ipsilateral disease, gynaecomastia and risk reduction. Results: One hundred and ninety-nine patients had a mastectomy to treat pure DCIS between 2000-2010. Median follow up time was 65 (0-152) months. 102 patients had an SSM compared to 97 who had a simple mastectomy. The mean age was younger in the SSM group 53 as opposed to 61 (p = &amp;lt;0.01, t-test). Overall local recurrence rates were 3.1% at 5 years and 5.6% at 8 years. Fiver-year contralateral recurrence rates were 4.2% and 8.5% at 8 years. All of the recurrences occurred in the SSM group which had 8/102 local recurrences compared to 0/97 in the simple mastectomy group. All 8 of the recurrence were invasive ductal carcinoma with a median disease free survival time of 55 months. Univariate analysis demonstrated that a young age and close margins predicted recurrence. Conclusion: Our overall 5-year local recurrence rate was 3.1%. This is higher than historical data however in line with emerging UK and US data. Five-year LRR was significantly higher after SSM 5.9% compared to simple mastectomy 0%. All recurrences were invasive disease, which represented a loss of control of disease. Further work is needed to evaluate if there is a benefit of undertaking post reconstruction mammography to detect recurrences whilst still in situ disease. Our work corroborates with the literature highlighting the importance of achieving clear margins to prevent recurrence. References: 1. Boyages et al, Cancer, 1999. 2. Wallis et al, British Journal of Cancer, 2012. 3. Carlson et al, Journal American College of Surgeons, 2007. 5 year recurrence rate following mastectomy for pure DCIS Simple (n=97)SSM (n=102) Ipsilateral LRR0%5.9%p = 0.01 1Contralateral RR4.8%3.2%p = 0.68 11 LogRank test Univariate factors predicting recurrence Recurrence (n=8)Non-Recurrence (n=191) Mean Age (years)48 (37-54)57 (33-81)p = 0.01 1Involved Margins (&amp;lt; 2mm)552p = 0.04 2High Grade8131p = 0.06 2ER negative557p = 0.14 2Size (mm)48 (20-80)38 (1-90)p = 0.33 11 T-test, 2 Chi-squared Citation Format: Timbrell SJ, Himdani SA, Shaw O, Morris J, Bundred NJ. Local recurrence rates after mastectomy undertaken for pure ductal carcinoma in situ. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-17-05.