Waiting times for radiotherapy: consequences of volume increase for the TCP in oropharyngeal carcinoma.
OBJECTIVE
Waiting lists for radiotherapy have become longer over the past years. Apart from the psychological distress for the patient we are concerned about tumour growth during this waiting time, which may worsen prognosis. The purpose of this pilot study was to investigate tumour growth in the waiting time and to obtain an indication of its clinical consequences for patients with oropharyngeal carcinoma. A tumour control probability (TCP) model was applied to evaluate consequences for outcome.


METHODS
Increase in tumour volume was measured for 13 patients with oropharyngeal carcinoma by outlining the tumour on the diagnostic as well as on the treatment planning CT scan. Waiting time was defined as time between histopathological diagnosis and start of radiotherapy. For each tumour we calculated the increase in tumour volume and the tumour doubling time. The potential increase in TCP was calculated for each tumour for the situation without treatment delay.


RESULTS
The mean increase in tumour volume was 70%. The mean waiting time was 56 days. Expected TCP with incorporation of delay was 47%, without delay it might have been 63-66%.


CONCLUSIONS
This study shows tumour progression during the time between the diagnostic CT scan and the treatment planning CT scan in oropharyngeal cancer. As a consequence of waiting time, which allows tumour volume increase, there may be an average control loss of 16-19 % for these tumours during the total waiting time before radiotherapy.
Department of Pediatric Surgery of the UMC Utrecht, Lundlaan 6, 3583 CX Utrecht, The Netherlands.
Annet
A
Waaijer
Chris H J
CH
Terhaard
Human
H
Dehnad
Gerrit-Jan
GJ
Hordijk
Maarten S
MS
van Leeuwen
Cornelius P J
CP
Raaymakers
Jan J W
JJ
Lagendijk
D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015233:Models, Statistical; D009959:Oropharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D017063:Outcome Assessment, Health Care; D010865:Pilot Projects; D011881:Radiotherapy, Computer-Assisted; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D014850:Waiting Lists