USMLE Step 1 Question 380

Question:

A 25-year-old professional cyclist is diagnosed with testicular cancer and undergoes chemotherapy. One month after beginning treatment, the patient complains of difficulty hearing. Which of the following chemotherapeutic agents is most likely responsible for this side effect?

Correct Answer: C.  Cisplatin

This question is testing your knowledge of the major toxicities of chemotherapeutic agents.

Cisplatin (choice C), an alkylating-like agent, crosslinks DNA thereby interfering with mitosis. It is known to cause nephrotoxicity and ototoxicity; both side effects seem to be related to the production of reactive oxygen species in specific tissues, leading to cell death.

Bleomycin (choice A) induces the formation of free radicals, which causes breaks in DNA strands. It is known to cause pulmonary fibrosis, skin changes and occasionally bone marrow suppression.

Busulfan (choice B) is a DNA alkylator and is known to cause pulmonary fibrosis and skin changes, including hyperpigmentation.

Cytarabine (choice D) inhibits DNA polymerase and causes megaloblastic anemia and pancytopenia.

Doxorubicin (choice E) generates free radicals and intercalates in DNA, creating breaks in the DNA. It causes cardiotoxicity, hair loss and bone marrow suppression.