Towards individualised radiotherapy for Stage I seminoma.
OBJECTIVE
Adjuvant radiotherapy is currently standard treatment of Stage I seminoma (SOS). The use of computerised tomogram (CT) planning is compared with traditional planning for greater treatment individualisation.


METHODS
Two plans were generated for each of 10 patients: one using traditional rectangular para-aortic fields, and one using conformal fields. The primary target volume compared was the dosimetric coverage of the inferior vena cava and aorta.


RESULTS
The dosimetric analysis of traditional plans showed that they provided reasonable dosimetric coverage of the CTV. However, if 1cm is used for uncertainty based on nodal coverage then the periphery of the PTV could be significantly under-dosed. The CT based plan delivered improved dosimetry to the vessel PTV compared with the traditional field (CT D 95=24.7 Gy, traditional D 95=23.6 Gy, P=0.002). CT-based plans were significantly wider than traditional plans (CT=11.8 cm, traditional=9 cm, P=0.002). The CT plan tended to irradiate relatively small volumes of the kidneys to higher doses.


CONCLUSIONS
Traditional para-aortic fields may deliver suboptimal dosimetry to an anatomically defined PTV. Our CT-based fields tend to be wider than traditional fields, and provide improved dosimetry to vessels based target volumes. Given that traditional fields are often delivering significantly less than the prescribed dose to the target volume, and that marginal relapses cause a high proportion of treatment failure, there is a suggestion that CT-based plans may avoid under-dosage and geographical miss sometimes seen with traditional plans.
Martin
Jarad M
JM
Radiation Oncology Centre, Austin Health, Vic., Australia. jarad.martin@rmp.uhn.on.ca
Joon
Daryl Lim
DL
Ng
Nicole
N
Grace
Michael
M
Gelderen
David Van
DV
Lawlor
Marita
M
Wada
Morikatsu
M
Joon
Michael Lim
ML
Quong
George
G
Khoo
Vincent
V
D019583:Dose Fractionation, Radiation; D006801:Humans; D008297:Male; D009919:Orchiectomy; D018714:Radiotherapy, Adjuvant; D020266:Radiotherapy, Conformal / Q000379:methods*; D012189:Retrospective Studies; D018239:Seminoma / Q000532:radiotherapy* / Q000601:surgery; D013736:Testicular Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D014057:Tomography, X-Ray Computed