**Core Concept**
Electron beam therapy is a type of radiation therapy that uses a beam of electrons to treat tumors. This modality is particularly useful for treating tumors that are located near critical structures, as the electron beam can be tailored to a specific depth, minimizing damage to surrounding tissues.

**Why the Correct Answer is Right**
Electron beam therapy is effective for treating basal cell carcinoma of the skin, as well as other superficial tumors. The electron beam can be adjusted to a depth that is equivalent to the thickness of the skin, allowing for precise targeting of the tumor while sparing underlying tissues. This is particularly useful for tumors located on the face, scalp, or hands, where damage to surrounding structures would be a significant concern.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect, as electron beam therapy is not typically used for treating brain tumors, which require more precise targeting and higher doses of radiation.
**Option B:** This option is incorrect, as electron beam therapy is not commonly used for treating pancreatic cancer, which often requires more aggressive treatment approaches.
**Option C:** This option is incorrect, as electron beam therapy is not typically used for treating prostate cancer, which is often treated with external beam radiation therapy or brachytherapy.

**Clinical Pearl / High-Yield Fact**
Electron beam therapy is particularly useful for treating superficial tumors, such as basal cell carcinoma, as it allows for precise targeting of the tumor while minimizing damage to surrounding tissues. This modality is often used as an alternative to surgery or other forms of radiation therapy.

**Correct Answer:** C.