# TDF Plan: Concomitant Boost

For 30 fractions of 180 cGy (54.0 Gy) given once a day, 5 days a week and at the same time (concomitant) a boost to a smaller field of 12 fractions of 150 cGy (18.0 Gy) once a day, you simply add the individual components. The primary component (include as course 1) has a biological effectiveness of 63.7 Gy(10.0) for acute effects. The cone down boost component (include as course 2) has a biological effectiveness of 20.7 Gy(10.0). Set the course start date in the course calendar window. TDF Plan will automatically determine if the courses are concomitant and indicate so by flagging course as Concomitant in red text next to the Tx days/week menu. This concomitant treatment has a biological effectiveness of 63.7 Gy(10.0) + 20.7 Gy(10.0) = 84.4 Gy(10.0) for acute effects and 113.4 Gy(3.0) for late effects. Compared with the hyperfractionation example, this concomitant boost is almost the same for late effects but less effective for acute effects, including tumor control.
The course calendar window will look like the picture below when planning the concomitant boost described above. The primary treatment (Course #1, shaded yellow) starts on August 14th. The concomitant cone down boost (Course #2, shaded green) will begin on September 10th.

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