Abstract | BACKGROUND: METHODS: A total of fifty patients with NPC were divided into two groups according to T-stages of T1-2 and T3-4, and the LCNs of each patient were contoured on CT simulation images. The targets were contoured based on the RTOG 0225 clinical trial and a working committee for clinical stage NPC in China in 2010. The NTCP differences in LCNs between the two plans were calculated. RESULTS: The LCN volume of the 50 patients was 10.07 cc. The Dmax and Dmean of LCNs in RTOG plans were significantly larger than those in reduced-volume plans (7,453 vs. 7,401 cGy, 6,740 vs. 6,436 cGy, P=0.004, 0.000), and these values were lower in the T1-2 group than in the T3-4 group (7,390 vs. 7,464 cGy, 6,442 vs. 6,733 cGy, P=0.019, 0.000). NTCP in RTOG plans was significantly higher than that in reduced-volume plans (59.98% vs. 51.62%, P=0.000), among which NTCP was significantly lower in the T1-2 group than in the T3-4 group (51.72% vs. 59.88%, P=0.002). There were strong correlations of NTCP with Dmean and irradiation volume for more than 6,600 cGy (R=0.847, P=0.000; R=0.841, P=0.000). CONCLUSIONS: the clinical T-stage, a high Dmean and a large irradiation volume are important factors in predicting LCN complications. Of the two most common IMRT guidance plans in China, the LCN NTCP based on the reduced-volume plan is significantly lower than that based on the RTOG plan.
|