Why is concurrent chemotherapy with radiotherapy used in locally advanced cancers?

• A. Chemotherapy acts as a radiosensitizer, enhancing tumor cell kill with radiation.
• B. It reduces imaging frequency.
• C. It eliminates the need for radiation fields.
• D. It prevents any acute toxicity.

Answer: (A)

Concurrent chemotherapy with radiotherapy is used because chemotherapy can act as a radiosensitizer, making tumor cells more vulnerable to the damage caused by radiation. By interfering with DNA repair and/or altering the cell cycle, these drugs increase the effectiveness of each radiation dose, leading to greater tumor cell kill than radiation alone. This synergy improves local control in locally advanced cancers where surgery isn’t feasible or where margins may be uncertain, and it can also help address micrometastatic disease systemically.

Other choices don’t fit the goal: reducing imaging frequency isn’t the purpose of combining therapies, and chemotherapy doesn’t replace the need for radiation fields. Nor does it prevent acute toxicity; in fact, concurrent treatment can heighten acute side effects, requiring careful management.