Which scenario reduces the lifetime cumulative dose of doxorubicin to 450 mg/m2?

• A. No cyclophosphamide
• B. No prior radiation
• C. Prior chest irradiation
• D. Concurrent radiotherapy

Answer: (C)

Doxorubicin’s risk of heart damage increases with the total amount a patient receives over time. When the heart has already been exposed to radiation, its tolerance to additional injury from chemotherapy is reduced, so clinicians tighten the safe lifetime limit on doxorubicin. Prior chest irradiation specifically lowers the approved cumulative dose to about 450 mg/m2 to help protect cardiac function. The other scenarios don’t by themselves mandate this particular reduction: removing cyclophosphamide doesn’t change doxorubicin’s cardiotoxic potential, and not having prior radiation would allow a higher cumulative dose. Concurrent radiotherapy also raises cardiac risk, but the situation described points to prior chest irradiation as the reason for the 450 mg/m2 cap.