Clinical Research Papers:
Clinical study of the time of repeated computed tomography and replanning for patients with nasopharyngeal carcinoma
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Xiujuan Gai1,2,*, Yumei Wei2,*, Hengmin Tao3,4, Jian Zhu5 and Baosheng Li2
1 School of Medicine and Life Sciences, University of Jinan-Shandong Academy of Medical Sciences, Shandong, China
2 Department of Radiation Oncology VI, Shandong Cancer Hospital Affiliated to Shandong University, Jinon, Shandong, China
3 Shandong Provincial Hospital affiliated to Shandong University, Shandong, China
4 Shandong Provincial Western Hospital, Shandong, China
5 Department of Radiation Oncology, Shandong Cancer Hospital Affiliated to Shandong University, Shandong, China
* These authors have contributed equally to this work
Baosheng Li, email:
Keywords: nasopharyngeal carcinoma (NPC), cone beam computed tomography (CBCT), gross tumor volume (GTV), parotid gland, displacement
Received: November 14, 2016 Accepted: March 09, 2017 Published: March 31, 2017
Purpose: To study the necessity of repeat computed tomography (CT) scan and replanning and know a more accurate time using weekly kilovoltage cone beam computed tomography (kV-CBCT) scans for patients with nasopharyngeal carcinoma (NPC) during radiotherapy.
Methods and Materials: Thirteen NPC patients treated with IMRT were enrolled into this prospective study. Weekly pretreatment kV-CBCT scans were performed on the 1st, 6th, 11st, 16th, 21st and 26th radiation time, respectively. Target delineations were contoured on all fractionated CBCT images, including the gross tumor volume of the primary nasopharyngeal tumor (GTVnx) and parotid glands. The volumes of GTVnx and parotid glands were calculated automatically using the Pinnacle3 8.0 system. Compared to the original GTVnx, the percentage of shrinking volume (ΔP) ≥ 50% was considered significantly.
Results: As the radiation proceeding, the GTVnx had a trend of shrinkage. Of all 13 patients, 11 cases (84.6%) had the volume shrinking ≥ 50% before the 21st radiation and 12 cases (92.3%) before the 26th radiation. And the parotid volume decreased significantly in the first four-week radiation, 6.45 ± 3.16cm3 (range, 3.06-13.9cm3) for the left parotid gland and 5.78 ± 2.39cm3 (range, 2.70-11.2cm3) for the right. Furthermore, only a little displacement occurred to bilateral parotid glands.
Conclusion: The replanning for NPC patients with IMRT is necessary, and the time between the 21st to 25th radiations is appropriate.
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