The Type of Breast Cancer Determines Effectiveness of Different Hormonal Therapies

According to the results of a recent study published in the Journal of Clinical Oncology, women with certain sub-types of hormone-positive breast cancer appear to benefit differently when treated with hormone therapy.

Hormone-positive breast cancer refers to breast cancer that is stimulated to grow from the female hormone, estrogen. Therefore, a standard treatment component for hormone-positive breast cancer includes an anti-estrogen agent that works to inhibit estrogen from stimulating cancer cells to grow.

The most common anti-estrogen used in the treatment of hormone-positive breast cancer is tamoxifen. Aromatase inhibitors (AIs) are another group of anti-estrogen drugs also used to treat hormone positive breast cancer.

Tamoxifen and AIs produce their anti-estrogen effects through different biologic pathways. Both tamoxifen and AIs are widely used but have different side effects.

Researchers recently evaluated 2,923 women to compare the effectiveness of tamoxifen and Femara® (letrozole), a commonly used AI, in different types of hormone-positive breast cancer.

Participants were divided into two main groups for the data evaluation: those with invasive ductal carcinoma (IDC), meaning the cancer started in the milk ducts, which are ducts that are responsible for carrying the milk from where it is produced to the nipples; and those with invasive lobular carcinoma (ILC), meaning the cancer started in the milk-producing lobules of the breast.

The researchers also evaluated data from two subtypes of breast cancer: luminal B (LB)-like, meaning the cancer cells are rapidly dividing; and luminal A (LA)-like, meaning the cancer cells are not dividing as rapidly.

  • Overall, Femara provided superior cancer-free survival compared to tamoxifen among patients with ILC – in both the LB-like and LA-like subtypes.
  • Among patients with IDC cancers, Femara provided superior cancer-free survival among patients with the LB-like subtype.
  • However, among patients with IDC cancers, Femara and tamoxifen provided similar cancer-free survival among the LA-like subtype.

The researchers concluded that Femara provides a greater magnitude of improvement in cancer-free survival than tamoxifen in hormone-positive IDC and ILC breast cancer, except for women diagnosed with IDC with the LA-like subtype. Among women with this type of breast cancer, Femara is comparable to tamoxifen.

These results will help guide healthcare providers to determine optimal treatment choices for individual patients, taking certain cancer characteristics into consideration.

Reference: Filho O, Giobbie-Hurder A, Mallon E, et al. Relative Effectiveness of Letrozole Compared With Tamoxifen for Patients With Lobular Carcinoma in the BIG 1-98 Trial. Journal of Clinical Oncology. 2015; 33 (25): 2772-2779.

 

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