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[Helical tomotherapy using simultaneously integrated boost and simultaneous integrated protection technique for unresectable biliary tract cancer].

Objective: To evaluate the safety and efficacy of helical tomotherapy using simultaneously integrated boost and simultaneous integrated protection technique in the treatment of unresectable biliary tract cancers. Methods: The data of 23 patients with unresectable biliary tract cancer who received tomotherapy-based hypofractionated radiotherapy at Comprehensive Cancer Centre of Drum Tower Hospital,the Affiliated Drum Tower Clinical College of Nanjing Medical University between February 2015 and October 2017 were analyzed. There were 10 males and 13 females, aged from 40 to 85 years(median:58 years). Pathological type included intrahepatic cholangiocarcinomas(n=11), gallbladder cancers(n=6),extrahepatic cholangiocarcinomas(n=6). The irradiated sites covered primary tumors and areas of local invasion,including metastatic lymph nodes which were confined to the abdominal or retroperitoneal space. Dose escalation was achieved using simultaneously integrated boost(SIB) technique, and simultaneous integrated protection(SIP)technique was used to protect gastrointestinal tracts and other adjacent organs. Cox regression modal and Kaplan-Meier analysis were used to analyze the associations between patients' characteristics and overall survival(OS). Results: The median total radiation dose was 54 Gy(range: 28-72 Gy)and median biologically effective dose(BED)was 74.4 Gy(range: 37.8-115.2 Gy).The median planning target volume(PTV)was 445.79 cm(3)(range:126.02-950.12 cm(3)). Based on the various PTV,patients received 2.4-6.0 Gy/fraction with 8-28 fractions. The local control rate was 65.2% and the median OS was 11.3 months(range:2.1-31.9 months).The most common cause of death was out-field failure and only 3 patients died of in-field failures. The longest survival was 31.9 months. BED≥70 Gy significantly improved OS,compared to BED<70 Gy(16.8 months vs.5.1 months)(HR=0.146, 95%CI:0.028-0.762, P=0.022). No patients developed grade ≥4 toxicities. Conclusions: Helical tomotherapy-based hypofractionated radiotherapy is effective and well tolerated for patients with unresectable biliary tract cancer. The dose escalation with higher BED could improve the survival for such patients.