Final answer:
An echocardiogram is the key test to order before administering doxorubicin due to the drug's potential cardiotoxic effects on the heart, thus ensuring the patient's heart function is adequate.
Step-by-step explanation:
The correct test to order prior to the administration of doxorubicin is an echocardiogram. Doxorubicin is an anthracycline chemotherapeutic agent used to detect cancer, determine the amount of cancer spread, and assess the effectiveness of treatment plans. However, doxorubicin can have cardiotoxic effects, making the assessment of heart function through an echocardiogram crucial to ensure patient safety. An echocardiogram will determine blood flow to the heart muscle and evaluate cardiac function before the patient is exposed to the potential cardiotoxic effects of doxorubicin. Unlike other tests listed, such as lower extremity dopplers, pulmonary function tests, and colonoscopies, the echocardiogram directly assesses heart health, which is vital given the cardiotoxic risks associated with doxorubicin.