A feasibility dosimetric study on prostate cancer : are we ready for a multicenter clinical trial on SBRT?
OBJECTIVE
The Italian Association of Medical Physics (AIFM) started a working group dedicated to stereotactic body radiotherapy (SBRT) treatment. In this work, we performed a multicenter planning study on patients who were candidates for SBRT in the treatment of prostate cancer with the aim of evaluating the dosimetric consistency among the different hospitals.


METHODS
Fourteen centers were provided the contours of 5 patients. Plans were performed following the dose prescription and constraints for organs at risk (OARs) of a reference paper. The dose prescription was 35 Gy in five fractions for the planning target volume (PTV). Different techniques were used (3D-CRT, fixed-Field IMRT, VMAT, CyberKnife). Plans were compared in terms of dose-volume histogram (DVH) parameters. Furthermore, the median DVH was calculated and one patient was re-planned.


RESULTS
A total of 70 plans were compared. The maximum dose to the body was 107.9 ± 4.5 % (range 101.5-116.3 %). Dose at 98 % (D98 %) and mean dose to the clinical target volume (CTV) were 102.0 ± 0.9 % (global range 101.1-102.9 %) and 105.1 ± 0.6 % (range 98.6-124.6 %). Similar trends were found for D95 % and mean dose to the PTV. Important differences were found in terms of the homogeneity index. Doses to OARs were heterogeneous. The subgroups with the same treatment planning system showed differences comparable to the differences of the whole group. In the re-optimized plans, DVH differences among institutes were reduced and OAR sparing improved.


CONCLUSIONS
Important dosimetric differences with possible clinical implications, in particular related to OARs, were found. Replanning allowed a reduction in the OAR dose and decreased standard deviations. Multicenter clinical trials on SBRT should require a preplanning study to standardize the optimization procedure.
Humanitas C.C.O., Catania, Italy.
Carmelo
C
Marino
Elena
E
Villaggi
Giulia
G
Maggi
Marco
M
Esposito
Lidia
L
Strigari
Elisa
E
Bonanno
Giusi R
GR
Borzì
Claudia
C
Carbonini
Rita
R
Consorti
David
D
Fedele
Christian
C
Fiandra
Isidora
I
Ielo
Tiziana
T
Malatesta
Maria Rosa
MR
Malisan
Anna
A
Martinotti
Renzo
R
Moretti
Barbara
B
Nardiello
Caterina
C
Oliviero
Stefania
S
Clemente
Pietro
P
Mancosu
D000368:Aged; D005240:Feasibility Studies; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk; D010347:Patient Care Planning; D056888:Patient Positioning; D011300:Preoperative Care; D011471:Prostatic Neoplasms / Q000601:surgery*; D011874:Radiometry / Q000379:methods; D016634:Radiosurgery / Q000379:methods*