**Core Concept**
Cardiotoxicity caused by radiotherapy and chemotherapy is a significant concern in oncology, as it can lead to cardiac dysfunction and increased risk of heart failure. This condition is often referred to as cardiotoxicity-induced cardiac damage or anthracycline cardiotoxicity. The underlying mechanism involves the generation of reactive oxygen species (ROS) and the disruption of cellular homeostasis.

**Why the Correct Answer is Right**
The correct answer involves the detection of troponin levels in the blood. Troponin is a cardiac-specific protein that is released into the bloodstream when cardiac muscle cells are damaged. Elevated troponin levels are a sensitive marker of cardiac injury and can be used to detect cardiotoxicity caused by radiotherapy and chemotherapy. This is because troponin is a highly specific marker of cardiac damage, and its elevation is closely associated with the extent of cardiac injury.

**Why Each Wrong Option is Incorrect**
* **Option A:** Echocardiography is a useful tool for assessing cardiac function, but it may not be sensitive enough to detect early changes in cardiac function caused by cardiotoxicity.
* **Option B:** Electrocardiogram (ECG) changes may be seen in patients with cardiotoxicity, but they are not specific and can be seen in other conditions as well.
* **Option C:** Cardiac biomarkers such as creatine kinase (CK) and lactate dehydrogenase (LDH) may be elevated in patients with cardiotoxicity, but they are not as sensitive or specific as troponin.

**Clinical Pearl / High-Yield Fact**
Troponin levels should be monitored regularly in patients undergoing radiotherapy and chemotherapy, especially those receiving anthracyclines or other cardiotoxic agents. Early detection of cardiotoxicity can lead to timely intervention and improved patient outcomes.

**Correct Answer: B. Echocardiography is a useful tool for assessing cardiac function but may not be sensitive enough to detect early changes in cardiac function caused by cardiotoxicity.