Regional lung density changes after radiation therapy for tumors in and around thorax.
OBJECTIVE
To study the temporal nature of regional lung density changes and to assess whether the dose-dependent nature of these changes is associated with patient- and treatment-associated factors.


METHODS
Between 1991 and 2004, 118 patients with interpretable pre- and post-radiation therapy (RT) chest computed tomography (CT) scans were evaluated. Changes in regional lung density were related to regional dose to define a dose-response curve (DRC) for RT-induced lung injury using three-dimensional planning tools and image fusion. Multiple post-RT follow-up CT scans were evaluated by fitting linear-quadratic models of density changes on dose with time as the covariate. Various patient- and treatment-related factors were examined as well.


RESULTS
There was a dose-dependent increase in regional lung density at nearly all post-RT follow-up intervals. The population volume-weighted changes evolved over the initial 6-month period after RT and reached a plateau thereafter (p < 0.001). On univariate analysis, patient age greater than 65 years (p = 0.003) and/or the use of pre-RT surgery (p < 0.001) were associated with significantly greater changes in CT density at both 6 and 12 months after RT, but the magnitude of this effect was modest.


CONCLUSIONS
There appears to be a temporal nature for the dose-dependent increases in lung density. Nondosimetric clinical factors tend to have no, or a modest, impact on these changes.
Ma
Jinli
J
Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27599-7512, USA.
Zhang
Junan
J
Zhou
Sumin
S
Hubbs
Jessica L
JL
Foltz
Rodney J
RJ
Hollis
Donna R
DR
Light
Kim L
KL
Wong
Terence Z
TZ
Kelsey
Christopher R
CR
Marks
Lawrence B
LB
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000704:Analysis of Variance; D001943:Breast Neoplasms / Q000532:radiotherapy; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000532:radiotherapy; D008223:Lymphoma / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011832:Radiation Injuries / Q000000981:diagnostic imaging*; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D055815:Young Adult