Abdominal cancer during early childhood: a dosimetric comparison of proton beams to standard and advanced photon radiotherapy.
OBJECTIVE
Evaluation of dosimetric benefits of advanced radiotherapy techniques for the treatment of abdominal lesions during early childhood.


METHODS
Treatment planning was performed for five Neuroblastoma (NBL) and four Wilms Tumor (WT) patients. Opposing fields (2F), photon intensity modulated radiotherapy (IMXT) and two proton techniques (passively scattered (PT) and scanned beams (IMPT)) were considered. Averaged dose-volume histograms, associated dosimetric parameters and a radiobiological model for the estimation of the therapy related carcinogenic effect were evaluated.


RESULTS
With respect to the 2F technique, both proton techniques enabled to reduce mean liver and kidney dose by 40-60%; Organ fractions irradiated at the level of the tolerance dose were reduced by 65% for kidneys and 75% for the liver in NBL patients and by additional 10% for WT patients. IMXT enabled to reduce parameters related to the steep high-dose gradient, e.g., V(15Gy) for the kidneys was reduced by a factor 2-3 compared to 2F. V(12Gy) was reduced by 40% in the liver. On the other side, the improvement of those parameters characterizing the low isodose domain was limited for IMXT. The risk for radiation-induced secondary cancer was doubled for IMXT and even more increased for PT if secondary neutrons were taken into account, while this risk remained the same or was reduced by IMPT with respect to 2F.


CONCLUSIONS
Proton beams improved all dosimetric parameters for NBL and WT patients compared to photon techniques. This improvement was limited for IMXT mainly to parameters related to the steep high-dose gradient. Further research is needed to minimize uncertainties for secondary cancer estimations.
Hillbrand
Martin
M
Department of Radiotherapy and Radiobiology, AKH Vienna, Medical University Vienna, Austria. Martin.Hillbrand@meduniwien.ac.at
Georg
Dietmar
D
Gadner
Helmut
H
Pötter
Richard
R
Dieckmann
Karin
K
D000008:Abdominal Neoplasms / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007680:Kidney Neoplasms / Q000532:radiotherapy*; D008099:Liver / Q000528:radiation effects; D008297:Male; D009447:Neuroblastoma / Q000532:radiotherapy*; D017785:Photons / Q000627:therapeutic use; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D018570:Risk Assessment; D016896:Treatment Outcome; D009396:Wilms Tumor / Q000532:radiotherapy*; D011522:Protons
D011522:Protons