## **Core Concept**
The question tests the understanding of anticancer drugs' ability to cross the blood-brain barrier (BBB), a critical aspect of treating brain tumors and metastases. The BBB is a highly selective semipermeable border that separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS).

## **Why the Correct Answer is Right**
The correct answer, , is known for its ability to cross the blood-brain barrier. This property makes it particularly useful in treating certain types of brain tumors. The drug's lipophilicity and molecular size contribute to its ability to penetrate the CNS.

## **Why Each Wrong Option is Incorrect**
* **Option A:** is not known for crossing the blood-brain barrier effectively. It is primarily used for cancers outside the CNS.
* **Option B:** also does not have significant penetration across the BBB, limiting its use in primary brain tumors or CNS metastases.
* **Option D:** has limited ability to cross the blood-brain barrier, making it less effective for treating CNS tumors compared to .

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the ability of anticancer drugs to cross the blood-brain barrier is crucial for the treatment of brain tumors and CNS metastases. is a classic example of a drug that can do so, making it relevant for certain cases.

## **Correct Answer:** .