**Core Concept**
Doxorubicin is an anthracycline antibiotic that intercalates DNA strands, thereby inhibiting the progression of topoisomerase II and inducing apoptosis in cancer cells. As a result of its mechanism of action, doxorubicin exhibits a unique side effect profile.

**Why the Correct Answer is Right**
Cardiotoxicity is a well-documented side effect of doxorubicin, primarily due to its ability to generate free radicals that damage cardiac tissue. This is mediated through the formation of reactive oxygen species (ROS) and the subsequent activation of various signaling pathways that lead to cardiomyocyte apoptosis. The anthracycline moiety of doxorubicin is responsible for its cardiotoxic effects, which can manifest as left ventricular dysfunction, heart failure, or even cardiogenic shock in severe cases.

**Why Each Wrong Option is Incorrect**
**Option A:** Pulmonary fibrosis is a common side effect of bleomycin, another chemotherapeutic agent, but not typically associated with doxorubicin.
**Option C:** Peripheral neuropathy is more commonly associated with agents like vincristine and cisplatin, which directly damage nerve tissue.
**Option D:** Hemorrhagic cystitis is a side effect of cyclophosphamide and ifosfamide, which are alkylating agents that produce acrolein as a toxic metabolite.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the cardiotoxic effects of doxorubicin can be mitigated by administering the anthracycline in a bolus fashion, rather than as a continuous infusion, and by using cardioprotective agents like dexrazoxane.

**✓ Correct Answer: B. Cardiotoxicity**