What is the difference between a treatment course and a fraction?

• A. A fraction is the entire plan; a course is one session.
• B. A course refers to the entire treatment plan with total dose; a fraction is a single treatment session dose.
• C. A course is the single dose; a fraction is the entire plan.
• D. A course equals the number of days; a fraction equals the frequency.

Answer: (C)

In radiotherapy, a fraction is the dose delivered in one treatment session, while a treatment course is the entire plan—the total prescribed dose planned across all sessions and the schedule over which those fractions are given. This distinction matters because fractionation lets normal tissue repair between sessions and shapes the overall biological effect on the tumor.

The correct way to state it is that the course equals the entire treatment plan with the total dose, and the fraction is a single treatment session dose. The other descriptions either swap these definitions or mix in days or frequency, which doesn’t match how treatment planning is structured.