Abstract 1788: Benefit of low-dose tamoxifen in a large, single-institution cohort of high-risk ER-positive DCIS
Authors: Guerrieri-Gonzaga Aliana , Sestak Ivana , Lazzeroni Matteo , Serrano Davide , Rotmensz Nicole , Cazzaniga Massimiliano , Varricchio Clara , Thorat Mangesh A. , Pruneri Giancarlo , Leonardi Maria Cristina , Galimberti Viviana , Bonanni Bernardo , DeCensi Andrea 
Published: July 2016

Abstract
Background: Low dose tamoxifen has shown comparable antiproliferative activity to 20 mg/day in biomarker trials, but its clinical efficacy is unclear. We assessed the effect of low dose tamoxifen, 10 mg on alternate day in most, on ipsilateral recurrence in high risk DCIS patients treated in a single institution.
Methods: Following breast conserving surgery, women with DCIS received radiotherapy and/or low dose tamoxifen as per clinical judgment and patient preference. Multivariate Cox regression analyses adjusted for potential confounding variables were performed.
Results: In a cohort of 1,091 women, median age was 53 years (IQR 46-62), 544 received radiotherapy versus 547 no radiotherapy. Of these, 883 had ER-positive DCIS, 467 received low-dose tamoxifen versus 416 no tamoxifen. After 7.7 years of median follow-up (IQR, 5.1-9.7), 235 ipsilateral recurrences and 62 contralateral tumors were observed. Low dose tamoxifen decreased any breast event (HR = 0.70, 95% CI, 0.54-0.91) and ipsilateral DCIS recurrence (HR = 0.66, 95% CI, 0.49-0.88), but not ipsilateral invasive recurrence (HR = 0.78, 95% CI, 0.56-1.09) or contralateral tumors (HR = 0.89, 95% CI, 0.51-1.55). Radiotherapy decreased any breast event (HR = 0.55, 95% CI, 0.42-0.72). Low dose tamoxifen was more effective in women aged &gt;50 years for all events (HR = 0.51, 95% CI, 0.33-0.77) and ipsilateral recurrences (HR = 0.43, 95% CI, 0.26-0.72) than in women aged 50 or younger (HR = 0.84, 95% CI, 0.60-1.18 and HR = 0.80, 95% CI, 0.55-1.16, respectively, p-interaction = 0.03). Young age or premenopausal status, positive margins, high Ki67, high grade and low BMI were independent predictors of ipsilateral recurrence. No increase in endometrial cancers was observed and fewer deaths occurred in women on low dose tamoxifen.
Conclusions: In high risk ER-positive DCIS, low-dose tamoxifen seems to be safe and effective in reducing ipsilateral recurrence, and represents a valuable option in women aged &gt;50 years. A randomized clinical trial is underway to confirm these results.
Supported by Lega Italiana per la Lotta contro i Tumori, AIRC, Italian Ministry of Health (RFPS-2006-1-339898), Gruppo bancario Credito Valtellinese.
Citation Format: Aliana Guerrieri-Gonzaga, Ivana Sestak, Matteo Lazzeroni, Davide Serrano, Nicole Rotmensz, Massimiliano Cazzaniga, Clara Varricchio, Mangesh A. Thorat, Giancarlo Pruneri, Maria Cristina Leonardi, Viviana Galimberti, Bernardo Bonanni, Andrea DeCensi. Benefit of low-dose tamoxifen in a large, single-institution cohort of high-risk ER-positive DCIS. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1788.