Which of the following is NOT typically considered a direct treatment for ER+ breast cancer?

Trastuzumab is not typically considered a direct treatment for estrogen receptor-positive (ER+) breast cancer because it specifically targets the HER2 protein, which is overexpressed in HER2-positive breast cancer cases. ER+ breast cancer, on the other hand, is characterized by the presence of estrogen receptors, and treatments for this type focus primarily on hormonal therapies or therapies aimed at blocking estrogen's effects.

In contrast, treatments like Exemestane and Fulvestrant are designed to inhibit estrogen production or block its receptors, directly addressing the hormone-dependent nature of ER+ breast cancer. Palbociclib is a targeted therapy that acts specifically on cancer cell cycle regulation but is often used in combination with hormonal therapies for ER+ cases, making it relevant in that context. However, trastuzumab does not have a direct application in treating ER+ tumors, which is why it stands out among the options as not being a direct treatment for this specific subtype of breast cancer.