Drug of choice for choriocarcinoma is?
**Core Concept**
Choriocarcinoma is a type of gestational trophoblastic disease (GTD) characterized by aggressive proliferation of cytotrophoblasts and syncytiotrophoblasts. It is a malignant neoplasm that arises from the placental tissue, typically following a molar pregnancy or spontaneous abortion.
**Why the Correct Answer is Right**
The drug of choice for choriocarcinoma is methotrexate, a folate antagonist that inhibits dihydrofolate reductase (DHFR) enzyme. This enzyme is crucial for the conversion of folic acid into tetrahydrofolate, which is essential for DNA synthesis and cell division. By inhibiting DHFR, methotrexate prevents the synthesis of DNA and RNA, leading to cell death. Methotrexate is effective in treating choriocarcinoma due to its ability to target rapidly dividing malignant cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Actinomycin D - While actinomycin D is used in the treatment of choriocarcinoma, it is typically reserved for patients who are resistant to methotrexate or have metastatic disease. It works by intercalating DNA and inhibiting RNA synthesis, but it is not the first-line treatment.
**Option B:** Cyclophosphamide - Cyclophosphamide is an alkylating agent that is used in the treatment of various types of cancer, but it is not the drug of choice for choriocarcinoma. It works by cross-linking DNA strands, leading to cell death, but it is not as effective as methotrexate in treating this specific malignancy.
**Option C:** Bleomycin - Bleomycin is a glycopeptide antibiotic that is used in the treatment of certain types of cancer, including testicular cancer and Hodgkin's lymphoma. However, it is not the drug of choice for choriocarcinoma.
**Clinical Pearl / High-Yield Fact**
Methotrexate is a high-risk medication that requires careful monitoring, particularly in patients with renal impairment or liver disease. It can cause hepatotoxicity, bone marrow suppression, and gastrointestinal toxicity, among other side effects.
**Correct Answer:** C. Methotrexate