title: Feasibility and response of helical tomotherapy in patients with metastatic colorectal cancer.
abstract: OBJECTIVE
  To investigate the treatment outcome and the toxicity of helical tomotherapy (HT) in patients with metastatic colorectal cancer (mCRC).
  
  
  METHODS
  We retrospectively reviewed 18 patients with 31 lesions from mCRC treated with HT between 2009 and 2013. The liver (9 lesions) and lymph nodes (9 lesions) were the most frequent sites. The planning target volume (PTV) ranged from 12 to 1,110 mL (median, 114 mL). The total doses ranged from 30 to 70 Gy in 10-30 fractions. When the α/β value for the tumor was assumed to be 10 Gy for the biologically equivalent dose (BED), the total doses ranged from 39 to 119 Gy10 (median, 55 Gy10). Nineteen lesions were treated with concurrent chemotherapy (CCRT).
  
  
  RESULTS
  With a median follow-up time of 16 months, the median overall survival for 18 patients was 33 months. Eight lesions (26%) achieved complete response. The 1- and 3-year local progression free survival (LPFS) rates for 31 lesions were 45% and 34%, respectively. On univariate analysis, significant parameters influencing LPFS rates were chemotherapy response before HT, aim of HT, CCRT, PTV, BED, and adjuvant chemotherapy. On multivariate analysis, PTV ≤113 mL and BED >48 Gy10 were associated with a statistically significant improvement in LFPS. During HT, four patients experienced grade 3 hematologic toxicities, each of whom had also received CCRT.
  
  
  CONCLUSIONS
  The current study demonstrates the efficacy and tolerability of HT for mCRC. To define optimal RT dose according to tumor size of mCRC, further study should be needed.
authors.affiliation: Department of Radiation Oncology, Soonchunhyang University College of Medicine, Bucheon, Korea.
authors.forename: Sun Hyun
authors.initials: SH
authors.lastname: Bae
authors.affiliation: Department of Radiation Oncology, Soonchunhyang University College of Medicine, Bucheon, Korea.
authors.forename: Seong Kwon
authors.initials: SK
authors.lastname: Moon
authors.affiliation: Department of Radiation Oncology, Catholic Kwandong University International St. Mary's Hospital, Incheon, Korea.
authors.forename: Yong Ho
authors.initials: YH
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Soonchunhyang University College of Medicine, Bucheon, Korea.
authors.forename: Kwang Hwan
authors.initials: KH
authors.lastname: Cho
authors.affiliation: Department of General Surgery, Soonchunhyang University College of Medicine, Bucheon, Korea.
authors.forename: Eung Jin
authors.initials: EJ
authors.lastname: Shin
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon, Korea.
authors.forename: Moon Sung
authors.initials: MS
authors.lastname: Lee
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon, Korea.
authors.forename: Chang Beom
authors.initials: CB
authors.lastname: Ryu
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon, Korea.
authors.forename: Bong Min
authors.initials: BM
authors.lastname: Ko
authors.affiliation: Division of Hematology-Oncology, Department of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon, Korea.
authors.forename: Jina
authors.initials: J
authors.lastname: Yun
keywords: Colorectal cancer; Helical tomotherapy; Metastases