From the Guidelines
Endocrine prophylaxis is not recommended for low-risk DCIS with low estrogen receptor (ER) expression of 8%. For DCIS, endocrine therapy with tamoxifen (20mg daily for 5 years) or aromatase inhibitors like anastrozole (1mg daily for 5 years) in postmenopausal women is typically reserved for cases with higher ER expression (usually >10%) 1. With only 8% ER positivity, the potential benefits of endocrine therapy would be minimal and likely outweighed by the risks of side effects, which include hot flashes, thromboembolic events, and endometrial cancer for tamoxifen, or bone density loss for aromatase inhibitors. The decision should be individualized based on the patient's overall risk profile, including factors such as age, family history, and other pathological features of the DCIS. Standard management for low-risk, low ER-expressing DCIS typically involves:
- Surgical excision with clear margins
- Possibly followed by radiation therapy depending on the extent of disease
- Close surveillance afterward rather than endocrine prophylaxis 1. According to the ASCO/CAP guideline update, breast cancer samples with 1% to 100% of tumor nuclei positive should be interpreted as ER positive, but cases with 1% to 10% staining should be reported as ER Low Positive, with a recommended comment explaining the more limited clinical data, heterogeneous behavior, and biology of this subgroup of ER-positive cancers 1.
From the FDA Drug Label
The decision regarding therapy with tamoxifen for the reduction in breast cancer incidence should be based upon an individual assessment of the benefits and risks of tamoxifen therapy. In women with DCIS, following breast surgery and radiation, tamoxifen citrate tablets are indicated to reduce the risk of invasive breast cancer
The use of tamoxifen for endocrine prophylaxis in patients with ER low (8%) DCIS is not directly addressed in the provided drug labels. However, it is indicated that tamoxifen can reduce the risk of invasive breast cancer in women with DCIS.
- The labels do not provide information on the specific ER status of the tumors in the studies.
- The decision to use tamoxifen should be based on an individual assessment of the benefits and risks of therapy.
- There is no direct information to support the use of endocrine prophylaxis in ER low (8%) DCIS 2, 2.
From the Research
Endocrine Prophylaxis in ER Low (8%) DCIS
- The decision to use endocrine prophylaxis in patients with ER low (8%) DCIS is complex and depends on various factors, including tumor characteristics, patient age, and treatment history 3, 4, 5, 6, 7.
- Studies have shown that endocrine therapy can reduce the risk of recurrence in patients with ER-positive DCIS, but the benefit is generally confined to those with higher levels of ER expression 6, 7.
- In patients with ER low (8%) DCIS, the benefit of endocrine prophylaxis is less clear, and the decision to use it should be individualized based on patient-specific factors 3, 5.
- The use of aromatase inhibitors, such as anastrozole, has been shown to be effective in reducing the risk of recurrence in postmenopausal women with hormone-receptor-positive DCIS, but the evidence for their use in patients with ER low (8%) DCIS is limited 4, 7.
- The National Surgical Adjuvant Breast and Bowel Project (NSABP) B-24 study demonstrated a significant reduction in the risk of recurrence with the use of tamoxifen in patients with ER-positive DCIS, but the study did not specifically address the use of endocrine prophylaxis in patients with ER low (8%) DCIS 6.
Factors Influencing the Decision to Use Endocrine Prophylaxis
- Patient age: Younger patients may be more likely to benefit from endocrine prophylaxis, while older patients may be at higher risk for adverse events 5, 7.
- Tumor characteristics: Patients with higher-grade tumors or larger tumors may be more likely to benefit from endocrine prophylaxis 3, 6.
- Treatment history: Patients who have undergone breast-conserving surgery or radiation therapy may be more likely to benefit from endocrine prophylaxis 3, 7.
- ER expression level: Patients with higher levels of ER expression are more likely to benefit from endocrine prophylaxis, while those with low ER expression (such as 8%) may not derive as much benefit 6, 7.