Final answer:
The cutoff to stop therapy with doxorubicin if there is a normal ejection fraction (EF) at baseline is typically when the EF decreases by more than 10 percentage points and falls below 50%, in order to prevent cardiotoxicity.
Step-by-step explanation:
The question relates to the use of doxorubicin, a chemotherapy medication, and the criteria for discontinuing its use based on cardiac function. Specifically, the question asks about the cutoff to stop therapy with doxorubicin if there is a normal ejection fraction (EF) at baseline. Doxorubicin is associated with cardiotoxicity, which can lead to heart failure. The standard practice is to monitor the patient's EF during treatment. If the EF decreases by more than 10 percentage points and falls below 50%, therapy with doxorubicin is typically halted to prevent further cardiac damage. This threshold is set to protect patients from potential heart damage while receiving chemotherapy.