| Objective:To evaluate the preliminary clinical outcome and the changes of target volume and organs at risk (OAR) during the helical tomotherapy (HT) for nasopharyngeal carcinoma(NPC).Methods:The retrospective review enrolled 43 patients with NPC treated with HT and had repeat CT imaging and replanning at twenty times during radiotherapy. Volume differences of target volume and OAR were compared between the two scans. Acute toxicities were evaluated with the established RTOG/EORTC criteria, and preliminary tumor response was evaluated at the same time.Results:Median interval between two scans was 25 days(23-28 days). When the second CT vs. the first CT was compared, the volumes of GTVnx and GTVnd decreased remarkably by 30.1% (median 29.8%),41.6% (median 45.9%), respectively. Furthermore, these changes were correlated with its primary volume and the change of GTVnd was correlated with weight lose. The volumes of left and right parotid glands decreased by 35.5% (median 33.4%),36.8% (median 33.5%), respectively. The axial diameters of head decreased 9.39(median 9.1%). Furthermore, all these changes were not correlated with different therapies. Acute toxicity was mostly Grade 1 to 2:skin 95%, salivary gland 100%, mucositis 93%. Six patients achieved complete remission (CR,14%),32 achieved partial remission (PR,74.4%) and 5 had stable disease (SD,11.6%) for the primary nasopharyngeal tumor. Sixteen patients achieved CR (37.2%),21 achieved PR (48.8%) and 1 had SD (2.3%) for regional lymph nodes. The remission rate of primary lesion and positive nodes were 88.4% and 94.9%, respectively. The median follow-up was 9 months. No local recurrence was detected. Two patients developed distant metastasis.Conclusion:The volume of target volumes and OAR were changed during helical tomotherapy. The clinical consequences of these changes maybe have potential dosimetric impact of target volume and/or overdosage of OAR. Therefore, repeat CT imaging and replanning during the course of HT for patients with NPC is essential. The incidence of severe acute toxicities is lower. Prolong follow-up is needed to prove its long-term result. |
