The goal of this study was to evaluate the actual anatomical and dosimetric changes of parotid glands in nasopharyngeal carcinoma patients during intensity modulated radiation therapy. With helical tomotherapy, its planning system, and adaptive software, weekly anatomical and dosimetric changes of parotid glands in 35 NPC patients were evaluated. Interweekly parotid volume varied significantly (P<0.03). The rate of volume change reached the highest level at the 16th fraction. The averageV1increased by 32.2 (left) and 28.6 (right), and the averageD50increased by 33.9 (left) and 24.93 (right), respectively. Repeat data comparison indicated that theV1andD50varied significantly among different fractions (both withP=0.000). The variation of parotid volume was inversely correlated with that of theV1andD50(both withP=0.000). In conclusion, parotid volume and actual dose vary significantly in NPC patients during IMRT. Replanning at the end of the fourth week of IMRT may have clinical benefits.
Helical tomotherapy provides efficacy similar to that of intensity-modulated radiation therapy with dosimetric benefits for endometrial carcinoma