A total of 12 patients (13.5%) took tamoxifen, including 10 with estrogen receptor-positive tumors.

In all, there were 27 patients who had estrogen receptor-positive tumors and had BCS or unilateral mastectomy. In this group, tamoxifen was recommended to 100% of the 10 patients who took it and 88% of the 17 patients who did not. 

Of the patients who did not take tamoxifen, 41% said that was mainly their decision, and 29% said they made the decision with their doctor. Data on decisional involvement and patients’ confidence in their decision was missing for 24% of patients. However, 35% said they were extremely confident in their decision to forgo ET, and 29% said they were very confident in the decision.

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Some patients did modify their lifestyle choices after DCIS diagnosis. Four patients quit smoking within 1 year of diagnosis, 8% (6/72) of patients lowered their alcohol consumption, and 73% (58/80) of patients reported engaging in more than 150 minutes of moderate-intensity physical activity weekly at 1 year after diagnosis. 

Modifying the Dose and Duration of ET

Some oncologists may consider ET to be worth the risks for patients with DCIS. The survey of the Young Women’s Breast Cancer Study cohort suggests that young women with DCIS may see the situation differently.2

Their responses indicate that patients understand the importance of reducing the risk of subsequent breast cancer-related events and are willing to make sacrifices to lower their risk. However, they often prefer mastectomy and exercise to BCS and ET. 

A review on adherence to ET suggested that less than half of patients with breast cancer will complete their prescribed 5 years of treatment.4 Factors associated with nonadherence included side effects, the perception of low recurrence risk, age extremes, medication cost, suboptimal patient-physician communication, and lack of social support.

A recent trial suggests that decreasing the dose and duration of ET could improve adherence by reducing side effects.5 The trial showed that patient-reported outcomes are generally similar in patients with breast proliferative lesions who receive placebo and those who receive a de-escalated dose (5 mg/day) and duration (3 years) of tamoxifen. 

The frequency of thromboembolism and endometrial cancer with the de-escalated dose and duration was lower than anticipated from the standard dose (20 mg/day) and duration (5 years) of tamoxifen. However, the de-escalated dose and duration provided a comparable reduction in breast cancer events as the standard. 

A real-world study of patients with noninvasive breast lesions who were offered ET showed that 76% of those who were given the option chose a de-escalated tamoxifen regimen.6 Ongoing research is investigating lower-intensity aromatase inhibitor regimens as chemoprevention.

Disclosures: Dr Hirst reported having a spouse/partner who is a stockholder in Nanostring, Gilead, Moderna, and Exact Sciences. Dr Tesch reported having no financial relationships to disclose.


1. O’Keefe TO, Yau C, Iaconetti E, et al. Duration of endocrine treatment for DCIS impacts second events: Insights from a large registry of cases at two academic medical centers. Presented at AACR Special Conference: Rethinking DCIS: An Opportunity for Prevention? September 8-11, 2022. Abstract PR008.

2. Tesch ME, Wong JS, Dominici L, et al. Breast cancer (BC) risk reduction in young women with ductal carcinoma in situ (DCIS). Presented at AACR Special Conference: Rethinking DCIS: An Opportunity for Prevention? September 8-11, 2022. Abstract PR009. 

3. Tesch ME, Rosenberg SM, Collins LC, et al. Clinicopathologic features, treatment patterns, and disease outcomes in a modern, prospective cohort of young women diagnosed with ductal carcinoma in situ. Ann Surg Oncol. Published online August 12, 2022. doi:10.1245/s10434-022-12361-y

4. Chlebowski RT, Kim J, Haque R. Adherence to endocrine therapy in breast cancer adjuvant and prevention settings. Cancer Prev Res. 2014;7(4):378-387. doi:10.1158/1940-6207.CAPR-13-0389

5. DeCensi A, Puntoni M, Guerrieri-Gonzaga A, et al. Randomized placebo controlled trial of low-dose tamoxifen to prevent local and contralateral recurrence in breast intraepithelial neoplasia. J Clin Oncol. 2019;37(19):1629-1637. doi:10.1200/JCO.18.01779

6. Patel R, Jin C, Tiersten A. Low-dose tamoxifen for breast cancer prevention in patients with ductal carcinoma in situ (DCIS) and atypical lesions: A real-world experience. J Clin Oncol. 2022;40(16 Suppl):e12537-e12537. doi:10.1200/JCO.2022.40.16_suppl.e12537