Abstract ES8-3: Endocrine management of premalignant lesions and DCIS

Abstract

Abstract It has been recognized for many years that there exist pathological entities associated with an increased risk of invasive breast cancer. The most frequently encountered are atypical hyperplasia (AH), lobular carcinoma in situ (LCIS) and ductal carcinoma in situ (DCIS), although other diagnoses have also been identified. Often these lesions are discovered incidentally, and when diagnosed are found to confer a wide range of elevated breast cancer risk. Clinical management of these conditions has largely consisted of surveillance, sometimes with the addition of endocrine therapy. The selective estrogen receptor modulators (SERMs), including tamoxifen and raloxifene, have been the mainstay of endocrine therapy in this setting. A prospective randomized trial, NSABP P-1 randomized over 13,000 high risk women, defined by a Gail score >1.66, to either 5 years of tamoxifen or placebo.1 Tamoxifen reduced the risk of invasive breast cancer by 49% (p<.00001), with the greatest risk reduction seen in women with ADH or LCIS. The IBIS I study also compared to tamoxifen to placebo and confirmed a risk reduction with tamoxifen, although lower than that reported initially in the P-1 trial (hazard ratio [HR] 0.72 [95% CI 0.59-0.88], p=0.001).2 Most recently, the role of aromatase inhibitors as chemoprevention in this setting has been studied; the results of IBIS II trial, which randomized 3864 high risk postmenopausal women to anastrozole or placebo, found a substantial risk reduction in the AI group (hazard ratio 0.47, 95% CI 0.32-0.68, p<0.0001).3 Endocrine therapy in the adjuvant setting has been reported for DCIS in two prospective clinical studies, the NSABP-B24 and UK/ANZ trials. A meta-analysis of these two trials demonstrated that tamoxifen after lumpectomy for DCIS reduced recurrence of both ipsilateral (HR 0.75; 95% CI 0.61 to 0.92) and contralateral (RR 0.50; 95% CI 0.28 to 0.87) DCIS.4 There was a trend towards decreased ipsilateral invasive cancer (HR 0.79; 95% CI 0.62 to 1.01) and reduced contralateral invasive cancer (RR 0.57; 95% CI 0.39 to 0.83). In addition, the findings of NSABP B-35 randomizing postmenopausal women with ER-positive DCIS reported that 10-year point estimates for DFS were 77.9% for tamoxifen and 82.7% for anastrozole.5 Future challenges for this field will include more precise patient selection for these treatments, as all confer risk of side effects. These have resulted in poor uptake of chemoprevention despite the definitive benefit demonstrated in the large randomized studies. In addition, the utility of endocrine therapy as primary treatment for low risk DCIS or in the neoadjuvant setting are important questions which are currently under investigation. More precise quantification and communication of the risks and benefits of the endocrine therapies will be increasingly needed in order to maximize the benefits of endocrine intervention in this setting. 1Fisher B, Costantino JP, Wickerham DL, et al: Tamoxifen for prevention of breast cancer: report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. J Natl Cancer Inst 90:1371-88, 1998 2Cuzick J, Sestak I, Cawthorn S, et al: Tamoxifen for prevention of breast cancer: extended long-term follow-up of the IBIS-I breast cancer prevention trial. Lancet Oncol 16:67-75, 2015 3Cuzick J, Sestak I, Forbes JF, et al: Anastrozole for prevention of breast cancer in high-risk postmenopausal women (IBIS-II): an international, double-blind, randomised placebo-controlled trial. Lancet 383:1041-8, 2014 4Staley H, McCallum I, Bruce J: Postoperative tamoxifen for ductal carcinoma in situ. Cochrane Database Syst Rev 10:CD007847, 2012 5Margolese RG: Primary Results of NRG Oncology/NSABP B-35: A Clinical Trial of Anastrozole vs Tamoxifen in Postmenopausal Patients with DCIS. J Clin Oncol 33, 2015 (suppl; abstr LBA500), 2015. Citation Format: Hwang ES. Endocrine management of premalignant lesions and DCIS. [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 ES8-3.