3-dimensional conformal radiation therapy in carcinoma of the nasopharynx

This study was designed to demonstrate the potential therapeutic advantage of 3-dimensional (3-D) treatment planning over the conventional 2-dimensional (2-D) approach in patients with carcinoma of the nasopharynx. The two techniques were compared both qualitatively and quantitatively for the boost portion of the treatment (19.8 Gy of a total 70.2 Gy treatment schedule) in patient with T4. The comparisons between 2-D and 3-D plans were made using dose statistics, dose-volume histogram, tumor control probabilities, and normal tissue complication probabilities. The 3-D treatment planning improved the dose homogeneity in the planning target volume. In addition, it caused the mean dose of the planning target volume to increase by 15.2% over 2-D planning. The mean dose to normal structures such as the temporal lobe, brain stem, parotid gland, and temporomandibular joint was reduced with the 3-D plan. The probability of tumor control was increased by 6% with 3-D treatment planning compared to the 2-D planning, while the probability of normal tissue complication was reduced. This study demonstrated the potential advantage of increasing the tumor control by using 3-D planning, but prospective studies are required to define the true clinical benefit