The use of in vivo thermoluminescent dosimeters in the quality assurance programme for the START breast fractionation trial.
OBJECTIVE
The use of in vivo dosimetry for patient measurement is recommended in many publications. It provides an additional check to verify that the dose delivered to the patient corresponds to the prescribed dose. In the context of a clinical trial investigating the effects of different fractionation regimens, it is imperative that the dose given is that prescribed to ensure that noise in the data between centres does not mask the results of the trial. The methodology for in vivo measurement in a clinical trial of breast radiotherapy was developed and verified.


METHODS
A cohort of patients in the STAndardisation of breast RadioTherapy (START) trial was monitored using postal thermoluminescent dosimeters chips (TLD). All TLD were processed and analysed at Mount Vernon Hospital. Patients for in vivo measurements were identified at randomisation as a random 1 in 9 samples for the first 2500 patients randomised (282 TLD) increasing to 1 in 3 thereafter. The TLD were left in place for the duration of the tangential field treatment and thus a composite entrance and exit dose was recorded.


RESULTS
TLD measurements were performed on 429 patients from 33 hospitals. The average ratio of dose measured using TLD to that prescribed was 0.99+/-0.04. Eight patients had initial measurements more than 10% different to the prescribed dose. The mean TLD results for a given centre correlated well with dose measurements performed using an ionisation chamber in a breast shaped phantom at that centre as part of the START trial audit.


CONCLUSIONS
Thermoluminescence dosimetry has provided useful quality assurance information on the doses received by patients in centres participating in the START trial.
Venables
Karen
K
Marie Curie Research Wing, Mount Vernon Hospital, Rickmansworth Road, Northwood, Middlesex HA6 2RN, UK.
Miles
Elizabeth A
EA
Aird
Edwin G A
EG
Hoskin
Peter J
PJ
D001943:Breast Neoplasms / Q000532:radiotherapy*; D015331:Cohort Studies; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D011785:Quality Assurance, Health Care / Q000379:methods; D011879:Radiotherapy Dosage / Q000592:standards; D013819:Thermoluminescent Dosimetry / Q000379:methods*; D006113:United Kingdom