Assessing the effect of a contouring protocol on postprostatectomy radiotherapy clinical target volumes and interphysician variation.
OBJECTIVE
To compare postprostatectomy clinical target volume (CTV) delineation before and after the introduction of a contouring protocol and to investigate its effect on interphysician variability


METHODS
Six site-specialized radiation oncologists independently delineated a CTV on the computed tomography (CT) scans of 3 patients who had received postprostatectomy radiotherapy. At least 3 weeks later this was repeated, but with the physicians adhering to the contouring protocol from the Medical Research Council's Radiotherapy and Androgen Deprivation In Combination After Local Surgery (RADICALS) trial. The volumes obtained before and after the protocol were compared and the effect of the protocol on interphysician variability assessed.


RESULTS
An increase in mean CTV for all patients of 40.7 to 53.9 cm(3) was noted as a result of observing the protocol, with individual increases in the mean CTV of 65%, 15%, and 24% for Patients 1, 2, and 3 respectively. A reduction in interphysician variability was noted when the protocol was used.


CONCLUSIONS
Substantial interphysician variation in target volume delineation for postprostatectomy radiotherapy exists, which can be reduced by the use of a contouring protocol. The RADICALS contouring protocol increases the target volumes when compared with those volumes typically applied at our center. The effect of treating larger volumes on the therapeutic ratio and resultant toxicity should be carefully monitored, particularly if the same dose-response as documented in radical prostate radiotherapy applies to the adjuvant and salvage setting. Prostate cancer, Postprostatectomy, Radiotherapy, Target volume.
Department of Clinical Oncology, Christie Hospital, Manchester, United Kingdom. dmmitchell@doctors.org.uk
Darren M
DM
Mitchell
Lesley
L
Perry
Steve
S
Smith
Tony
T
Elliott
James P
JP
Wylie
Richard A
RA
Cowan
Jacqueline E
JE
Livsey
John P
JP
Logue
D000368:Aged; D001822:Body Burden; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D017430:Prostate-Specific Antigen / Q000097:blood; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000097:blood / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D011829:Radiation Dosage; D018787:Radiation Oncology / Q000592:standards*; D018714:Radiotherapy, Adjuvant; D014057:Tomography, X-Ray Computed
D017430:Prostate-Specific Antigen