Compared planning dosimetry of TOMO, VMAT and IMRT in rectal cancer with different simulated positions.
OBJECTIVE
To compare treatment plans for helical tomotherapy (TOMO), volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) for locally advanced rectal cancer (LARC).


METHODS
This retrospective study from December 2010 to June 2013 included 20 patients with LARC who received neoadjuvant concurrent chemoradiotherapy (CCRT) with radiation doses of greater than 50.4 Gy. Dosimetric quality was evaluated based on doses to organs at risk (OARs), including small bowel, urinary bladder and bilateral femoral head, over the same coverage of the clinical target volume (CTV).


RESULTS
In supine comparison of IMRT with VMAT, VMAT treatment plan had a lower hot spot dose (p=0.0154) and better conformity index (CI, p=0.0036) and homogeneity index (HI, p=0.0246). Lower bladder V34.98 (p=0.0008), V40 (p=0.0058), mean dose (p<0.0001), femoral head mean dose (p=0.0089), V30 (p<0.0001), V40 (p=0.0013) and better CI (p<0.0001) and HI (p=0.0001) were observed for TOMO compared with IMRT. Patients with LARC receiving TOMO planning had lower bladder V34.98 (p=0.0021), V40 (p=0.0055), mean dose (p=0.0039), femoral head mean dose (p=0.0060), V30 (p<0.0001), and V40 (p=0.0044) and better CI (p=0.0157) and HI (p=0.0292) than VMAT. Comparing prone and supine position image planning, there were no significant differences, including in OARs in the three planning systems, except for lower bladder V34.98 (p=0.0403) in the supine position using TOMO.


CONCLUSIONS
Using modern radiation techniques, neither prone nor supine positions provide better values for OARs. TOMO was superior to IMRT and VMAT in sparing OARs and planning quality parameters.
Department of Radiation Oncology, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan, ROC.|Department of Radiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan, ROC.|Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan, ROC.|Department of Radiation Oncology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, ROC.
Jang-Chun
JC
Lin
Department of Radiation Oncology, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan, ROC.|Department of Radiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan, ROC.
Jo-Ting
JT
Tsai
Department of Radiation Oncology, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan, ROC.
Li-Jhen
LJ
Chen
Department of Radiation Oncology, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan, ROC.
Ming-Hsien
MH
Li
Department of Neurological Surgery, Tri-Service General Hospital and National Defense Medical Center, Taipei, Taiwan, ROC.|Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan, ROC.
Wei-Hsiu
WH
Liu
D000328:Adult; D000368:Aged; D059248:Chemoradiotherapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D058958:Organs at Risk; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012004:Rectal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D012189:Retrospective Studies
helical tomotherapy (TOMO); intensity modulated radiotherapy (IMRT); radiation dosimetry; rectal cancer (RC); volumetric modulated arc therapy (VMAT)