Which of the following is a characteristic of hormonal therapy for breast cancer?

Hormonal therapy for breast cancer specifically targets estrogen-sensitive tumors, making it a critical treatment option for patients whose tumors are influenced by hormonal factors. This type of therapy works by blocking estrogen's effects on the tumor or lowering estrogen levels in the body, thereby slowing or stopping the growth of these cancer cells.

This characteristic is particularly relevant in the context of cancers that are hormone receptor-positive, meaning they grow in response to hormones like estrogen and/or progesterone. By effectively blocking these hormone receptors or reducing hormone production, hormonal therapy can improve outcomes for patients diagnosed with this type of breast cancer.

In contrast, other options do not accurately represent the nature of hormonal therapy. Hormonal therapy does not generally target the immune system, is not a part of every breast cancer treatment regimen (nor is it synonymous with chemotherapy), and is only suitable for specific types of breast cancer, primarily those that are hormone receptor-positive.