The influence of changes in tumor hypoxia on dose-painting treatment plans based on 18F-FMISO positron emission tomography.
OBJECTIVE
To evaluate how changes in tumor hypoxia, according to serial fluorine-18-labeled fluoro-misonidazole (18F-FMISO) positron emission tomography (PET) imaging, affect the efficacy of intensity-modulated radiotherapy (IMRT) dose painting.


METHODS
Seven patients with head and neck cancers were imaged twice with FMISO PET, separated by 3 days, before radiotherapy. Intensity-modulated radiotherapy plans were designed, on the basis of the first FMISO scan, to deliver a boost dose of 14 Gy to the hypoxic volume, in addition to the 70-Gy prescription dose. The same plans were then applied to hypoxic volumes from the second FMISO scan, and the efficacy of dose painting evaluated by assessing coverage of the hypoxic volumes using Dmax, Dmin, Dmean, D95, and equivalent uniform dose (EUD).


RESULTS
Similar hypoxic volumes were observed in the serial scans for 3 patients but dissimilar ones for the other 4. There was reduced coverage of hypoxic volumes of the second FMISO scan relative to that of the first scan (e.g., the average EUD decreased from 87 Gy to 80 Gy). The decrease was dependent on the similarity of the hypoxic volumes of the two scans (e.g., the average EUD decrease was approximately 4 Gy for patients with similar hypoxic volumes and approximately 12 Gy for patients with dissimilar ones).


CONCLUSIONS
The changes in spatial distribution of tumor hypoxia, as detected in serial FMISO PET imaging, compromised the coverage of hypoxic tumor volumes achievable by dose-painting IMRT. However, dose painting always increased the EUD of the hypoxic volumes.
Lin
Zhixiong
Z
Department of Radiation Oncology, Shantou University Medical College-Cancer Hospital, Shantou, China.
Mechalakos
James
J
Nehmeh
Sadek
S
Schoder
Heiko
H
Lee
Nancy
N
Humm
John
J
Ling
C Clifton
CC
D015687:Cell Hypoxia; D005240:Feasibility Studies; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism / Q000532:radiotherapy; D006801:Humans; D008920:Misonidazole / Q000031:analogs & derivatives*; D049268:Positron-Emission Tomography / Q000379:methods*; D011836:Radiation Tolerance; D011838:Radiation-Sensitizing Agents; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated
D011838:Radiation-Sensitizing Agents; C031843:fluoromisonidazole; D008920:Misonidazole