Dosimetry audit for a multi-centre IMRT head and neck trial.
OBJECTIVE
PARSPORT was a multi-centre randomised trial in the UK which compared Intensity-Modulated Radiotherapy (IMRT) and conventional radiotherapy (CRT) for patients with head and neck cancer. The dosimetry audit goals were to verify the plan delivery in participating centres, ascertain what tolerances were suitable for head and neck IMRT trials and develop an IMRT credentialing program.


METHODS
Centres enrolling patients underwent rigorous quality assurance before joining the trial. Following this each centre was visited for a dosimetry audit, which consisted of treatment planning system tests, fluence verification films, combined field films and dose point measurements.


RESULTS
Mean dose point measurements were made at six centres. For the primary planning target volume (PTV) the differences with the planned values for the IMRT and CRT arms were -0.6% (1.8% to -2.4%) and 0.7% (2.0% to -0.9%), respectively. Ninety-four percent of the IMRT fluence films for individual fields passed gamma criterion of 3%/3mm and 75% of the films for combined fields passed gamma criterion 4%/3mm (no significant difference between dynamic delivery and step and shoot delivery).


CONCLUSIONS
This audit suggests that a 3% tolerance could be applied for PTV point doses. For dose distributions tolerances of 3%/3mm on individual fields and 4%/3mm for combined fields are proposed for multi-centre head and neck IMRT trials.
Clark
Catharine H
CH
Department of Physics, Royal Marsden NHS Foundation Trust, London, UK. catharine.clark@rmh.nhs.uk
Hansen
Vibeke Nordmark
VN
Chantler
Hannah
H
Edwards
Craig
C
James
Hayley V
HV
Webster
Gareth
G
Miles
Elizabeth A
EA
Guerrero Urbano
M Teresa
MT
Bhide
Shree A
SA
Bidmead
A Margaret
AM
Nutting
Christoper M
CM
D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008485:Medical Audit; D008875:Middle Aged; D009367:Neoplasm Staging; D011446:Prospective Studies; D011786:Quality Control; D011836:Radiation Tolerance; D011859:Radiography; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012307:Risk Factors; D016896:Treatment Outcome