Daily megavoltage computed tomography in lung cancer radiotherapy: correlation between volumetric changes and local outcome.
OBJECTIVE
To assess the predictive or comparative value of volumetric changes, measured on daily megavoltage computed tomography during radiotherapy for lung cancer.


METHODS
We included 80 patients with locally advanced non-small-cell lung cancer treated with image-guided intensity-modulated radiotherapy. The radiotherapy was combined with concurrent chemotherapy, combined with induction chemotherapy, or given as primary treatment. Patients entered two parallel studies with moderately hypofractionated radiotherapy. Tumor volume contouring was done on the daily acquired images. A regression coefficient was derived from the volumetric changes on megavoltage computed tomography, and its predictive value was validated. Logarithmic or polynomial fits were applied to the intratreatment changes to compare the different treatment schedules radiobiologically.


RESULTS
Regardless of the treatment type, a high regression coefficient during radiotherapy predicted for a significantly prolonged cause-specific local progression free-survival (p = 0.05). Significant differences were found in the response during radiotherapy. The significant difference in volumetric treatment response between radiotherapy with concurrent chemotherapy and radiotherapy plus induction chemotherapy translated to a superior long-term local progression-free survival for concurrent chemotherapy (p = 0.03). An enhancement ratio of 1.3 was measured for the used platinum/taxane doublet in comparison with radiotherapy alone.


CONCLUSIONS
Contouring on daily megavoltage computed tomography images during radiotherapy enabled us to predict the efficacy of a given treatment. The significant differences in volumetric response between treatment strategies makes it a possible tool for future schedule comparison.
Bral
Samuel
S
Department of Radiation Oncology, Oncology Center, Universitair Ziekenhuis Brussel, Brussels, Belgium. samuelbral@yahoo.co.uk
De Ridder
Mark
M
Duchateau
Michaël
M
Gevaert
Thierry
T
Engels
Benedikt
B
Schallier
Denis
D
Storme
Guy
G
D000368:Aged; D000704:Analysis of Variance; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy; D003131:Combined Modality Therapy / Q000379:methods; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012074:Remission Induction / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D047368:Tumor Burden / Q000528:radiation effects*