BACKGROUND AND PURPOSE: To assess anatomic changes during intensity modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) and to determine its dosimetric impact. PATIENTS AND METHODS: Twenty patients treated with IMRT for NPC were enrolled in this study. A second CT was performed at 38 Gy. Manual contouring of the macroscopic tumor volumes (GTV) and the planning target volumes (PTV) were done on the second CT. We recorded the volumes of the different structures, D98 %, the conformity, and the homogeneity indexes for each PTV. Volume percent changes were calculated. RESULTS: We observed a significant reduction in tumor volumes (58.56 % for the GTV N and 29.52 % for the GTV T). It was accompanied by a significant decrease in the D98 % for the 3 PTV (1.4 Gy for PTV H, p = 0.007; 0.3 Gy for PTV I, p = 0.03 and 1.15 Gy for PTV L, p = 0 0.0066). In addition, we observed a significant reduction in the conformity index in the order of 0.02 (p = 0.001) and 0.01 (p = 0.007) for PTV H and PTV I, respectively. The conformity variation was not significant for PTV L. Moreover, results showed a significant increase of the homogeneity index for PTV H (+ 0.03, p = 0.04) and PTV L (+ 0.04, p = 0.01). CONCLUSION: Tumor volume reduction during the IMRT of NPC was accompanied by deterioration of the dosimetric coverage for the different target volumes. It is essential that a careful adaptation of the treatment plan be considered during therapy for selected patients.
BACKGROUND AND PURPOSE: To assess anatomic changes during intensity modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) and to determine its dosimetric impact. PATIENTS AND METHODS: Twenty patients treated with IMRT for NPC were enrolled in this study. A second CT was performed at 38 Gy. Manual contouring of the macroscopic tumor volumes (GTV) and the planning target volumes (PTV) were done on the second CT. We recorded the volumes of the different structures, D98 %, the conformity, and the homogeneity indexes for each PTV. Volume percent changes were calculated. RESULTS: We observed a significant reduction in tumor volumes (58.56 % for the GTV N and 29.52 % for the GTV T). It was accompanied by a significant decrease in the D98 % for the 3 PTV (1.4 Gy for PTV H, p = 0.007; 0.3 Gy for PTV I, p = 0.03 and 1.15 Gy for PTV L, p = 0 0.0066). In addition, we observed a significant reduction in the conformity index in the order of 0.02 (p = 0.001) and 0.01 (p = 0.007) for PTV H and PTV I, respectively. The conformity variation was not significant for PTV L. Moreover, results showed a significant increase of the homogeneity index for PTV H (+ 0.03, p = 0.04) and PTV L (+ 0.04, p = 0.01). CONCLUSION: Tumor volume reduction during the IMRT of NPC was accompanied by deterioration of the dosimetric coverage for the different target volumes. It is essential that a careful adaptation of the treatment plan be considered during therapy for selected patients.
Authors: Vincent Grégoire; Kian Ang; Wilfried Budach; Cai Grau; Marc Hamoir; Johannes A Langendijk; Anne Lee; Quynh-Thu Le; Philippe Maingon; Chris Nutting; Brian O'Sullivan; Sandro V Porceddu; Benoit Lengele Journal: Radiother Oncol Date: 2013-10-31 Impact factor: 6.280
Authors: Eric K Hansen; M Kara Bucci; Jeanne M Quivey; Vivian Weinberg; Ping Xia Journal: Int J Radiat Oncol Biol Phys Date: 2005-10-26 Impact factor: 7.038
Authors: Jerry L Barker; Adam S Garden; K Kian Ang; Jennifer C O'Daniel; He Wang; Laurence E Court; William H Morrison; David I Rosenthal; K S Clifford Chao; Susan L Tucker; Radhe Mohan; Lei Dong Journal: Int J Radiat Oncol Biol Phys Date: 2004-07-15 Impact factor: 7.038
Authors: Kenneth C W Wong; Edwin P Hui; Kwok-Wai Lo; Wai Kei Jacky Lam; David Johnson; Lili Li; Qian Tao; Kwan Chee Allen Chan; Ka-Fai To; Ann D King; Brigette B Y Ma; Anthony T C Chan Journal: Nat Rev Clin Oncol Date: 2021-06-30 Impact factor: 66.675