Background: To evaluate dosimetric differences of salvage irradiations using two commercially available volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) techniques: RapidArc (RA) and HyperArc (HA), for recurrent nasopharyngeal carcinoma (NPC) after initial radiation therapy. Methods: Ten patients with recurrent NPC status previously treated with radiation therapy were considered suitable candidates for salvage SBRT using VMAT approach. Two separate treatment plans were created with HA and RA techniques for each case, with dosimetric outcomes compared with respect to tumor target coverage and organs-atrisk (OARs) sparing. Furthermore, the cumulative radiobiological effects to the relevant OARs from the original radiotherapy to the respective salvage SBRT plans were analyzed in terms of biologically effective dose (BED). Results: Treatment with HA exhibited similar target dose coverage as with RA, while delivering a higher mean dose to the targets. Using RA technique, the mean maximal doses to optic apparatus and the mean brain dose were reduced by 1 to 1.5 Gy, comparing to HA technique. The conformity index, gradient radius, and intermediate dose spillage in HA plans were significantly better than those in RA. With HA technique, the volume of brain receiving 12 Gy or more was reduced by 44%, comparing to RA technique. The cumulative BEDs to spinal cord and optic apparatus with RA technique were 1 to 2 Gy 3 less than those with HA. HA technique significantly reduced the volume within body that received more than 100 Gy. Conclusions: With better dose distribution than RA while maintaining sufficient target dose coverage, HA represents an attractive salvage SBRT technique for recurrent NPC.
lesions, maximum tumor diameter (MTD), combined TACE, radiotherapy dose were included in analysis of prognosis. Results: All patients were treated with intensity modulated radiotherapy by conventional fraction of 2Gy/f. The median dose was 50Gy (28-66Gy). Response rate (RR, complete response + partial response) was 55.7% when considering all lesions of whole body. In field of RT, RR of the primary tumor was 77.1% and RR of the tumor thrombosis was 83.7%. The 2-year overall survival was 29.9% and median survival time (MST) was 13.6 months. Median time to progression (TTP) was 4.7 months. The 2-year progression free survival of tumor thrombosis was 88.6%. Multivariate analysis showed that the MTD>10cm was an independent poor prognostic factor of TTP (HR, 1.961, 95%CI, 1.034-3.717). TTP in patients with MTD 10cm and MTD>10cm were 5.0 months and 3.3 months (pZ0.026), respectively. However, for MST, combination of TACE (both before or after RT) was an independent favor prognostic factor (HR, 0.184, 95%CI, 0.06-0.565). MST of combination therapy was 15 months, and MST of patients receiving radiotherapy alone was 4 months (p<0.001). Of all patients, grade III or higher liver function damage was 1.6%, and no lethal radiation-induced liver disease occurred. Grade III or higher hematological toxicity was 11.5%. Conclusion: The tumor thrombosis is more sensitive to radiation therapy than the primary tumor. Radiotherapy improves survival by the perfect control of tumor thrombosis. Progression of outside field of RT is primary failure mode for patients with main PVTT. Combination of radiotherapy and TACE is benefit to survivals.
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