A broadly adaptive array of dose-constraint templates for planning of intensity-modulated radiation therapy for advanced T-stage nasopharyngeal carcinoma.
OBJECTIVE
To develop and validate adaptive dose-constraint templates in intensity-modulated radiotherapy (IMRT) planning for advanced T-stage nasopharyngeal carcinoma (NPC).


METHODS
Dose-volume histograms of clinically approved plans for 20 patients with advanced T-stage NPC were analyzed, and the pattern of distribution in relation to the degree of overlap between targets and organs at risk (OARs) was explored. An adaptive dose constraint template (ADCT) was developed based on the degree of overlap. Another set of 10 patients with advanced T-stage NPC was selected for validation. Results of the manual arm optimization protocol and the ADCT optimization protocol were compared with respect to dose optimization time, conformity indices, multiple-dose end points, tumor control probability, and normal tissue complication probability.


RESULTS
For the ADCT protocol, average time required to achieve an acceptable plan was 9 minutes, with one optimization compared with 94 minutes with more than two optimizations of the manual arm protocol. Target coverage was similar between the manual arm and ADCT plans. A more desirable dose distribution in the region of overlap between planning target volume and OARs was achieved in the ADCT plan. Dose end points of OARs were similar between the manual arm and ADCT plans.


CONCLUSIONS
With the developed ADCT, IMRT treatment planning becomes more efficient and less dependent on the planner's experience on dose optimization. The developed ADCT is applicable to a wide range of advanced T-stage NPC treatment and has the potential to be applied in a broader context to IMRT planning for other cancer sites.
Chau
Ricky Ming-Chun
RM
Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong, SAR, China.
Leung
Sing-Fai
SF
Kam
Michael Koon-Ming
MK
Cheung
Kin-Yin
KY
Kwan
Wing-Hon
WH
Yu
Kwok-Hung
KH
Chiu
Kwok-Wing
KW
Cheung
Michael Lok-Man
ML
Chan
Anthony Tak-Cheung
AT
D001933:Brain Stem / Q000528:radiation effects; D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D009367:Neoplasm Staging; D009897:Optic Chiasm / Q000528:radiation effects; D009900:Optic Nerve / Q000528:radiation effects; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods / Q000592:standards; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods* / Q000592:standards; D013116:Spinal Cord / Q000528:radiation effects; D013997:Time Factors; D047368:Tumor Burden