Functional Image-Guided Radiotherapy Planning in Respiratory- Gated Intensity-Modulated Radiation Therapy (IMRT) for Lung Cancer Patients with chronic obstructive pulmonary disease (COPD)
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(Purpose) To investigate the incorporation of functional lung image-derived low attenuation area (LAA) based on four-dimensional computed tomography (4D-CT) into respiratory-gated intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) in treatment planning for lung cancer patients with chronic obstructive pulmonary disease (COPD).
(Materials and Methods) Eight lung cancer patients with COPD were the subjects of this study. LAA was generated from 4D-CT data sets according to CT values lower than -860 Hounsfield units (HU) as a threshold. The functional lung image was defined as the area where LAA was excluded from the image of the total lung. Two respiratory-gated radiotherapy plans (70 Gy/35 fr) were designed and compared in each patient as follows: 1) Plan A: anatomical IMRTor VMAT plan based on the total lung 2) Plan F: functional IMRT or VMAT plan based on the functional lung. Dosimetric parameters (V20: the percentage of total lung volume irradiated with ≥ 20 Gy,MLD:mean dose of total lung) of the two plans were compared.
(Results) V20 was lower in Plan F than in Plan A (mean 1.5 %, p= 0.025 in IMRT, mean 1.6 %, p= 0.044 in VMAT) achieved by a reduction in MLD (mean 0.23 Gy, p= 0.083 in IMRT, mean 0.5 Gy, p= 0.042 in VMAT). No differences were noted in target volume coverage and organ-at-risk doses.
(Conclusions) Functional image-guided radiotherapy planning based on LAAin respiratory-guided IMRT or VMAT appears to be effective in preserving a functional lung in lung cancer patients with COPD.
This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan (Grant no. 22591385), and a Grant-in-Aid for Scientific Research from the Association for Nuclear Technology in Medicine.
This work was partly presented at the 52nd Annual Meeting of the American Society of Radiation Oncology, San Diego, CA, Oct 31 - Nov 4, 2010.
International Journal of Radiation Oncology, Biology, Physics
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