Dosimetric evaluation of a three-phase adaptive radiotherapy for nasopharyngeal carcinoma using helical tomotherapy

Journal Article · Sun Apr 01 04:00:00 EDT 2012 · Medical Dosimetry

DOI:https://doi.org/10.1016/J.MEDDOS.2011.01.006· OSTI ID:22130386

Wu, Vincent Wing Cheung ^[1]; Teo, Peter Man Lung ^[2]

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1. Department of Health Technology and Informatics, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong)
2. Central Comprehensive Cancer Centre, Central (Hong Kong)

Adaptive radiotherapy (ART) has been introduced to correct the radiation-induced anatomic changes in head and neck cases during a treatment course. This study evaluated the potential dosimetric benefits of applying a 3-phase adaptive radiotherapy protocol in nasopharyngeal carcinoma (NPC) patients compared with the nonadaptive single-phase treatment protocol. Ten NPC patients previously treated with this 3-phase radiation protocol using Hi-Art Tomotherapy were recruited. Two new plans, PII-ART and PIII-ART, were generated based on the up-to-date computed tomography (CT) images and contours and were used for treatment in phase two (PII; after 25th fraction) and phase three (PIII; after 35th fraction), respectively. To simulate the situation of no replanning, 2 hybrid plans denoted as PII-NART and PIII-NART were generated using the original contours pasted on the PII- and PIII-CT sets by CT-CT fusion. Dosimetric comparisons were made between the NART plans and the corresponding ART plans. In both PII- and PIII-NART plans, the doses to 95% of all the target volumes (D{sub 95}) were increased with better dose uniformity, whereas the organs at risk (OARs) received higher doses compared with the corresponding ART plans. Without replanning, the total dose to 1% of brainstem and spinal cord (D{sub 1}) significantly increased 7.87 {+-} 7.26% and 10.69 {+-} 6.72%, respectively (P = 0.011 and 0.001, respectively), in which 3 patients would have these structures overdosed when compared with those with two replannings. The total maximum doses to the optic chiasm and pituitary gland and the mean doses to the left and right parotid glands were increased by 10.50 {+-} 10.51%, 8.59 {+-} 6.10%, 3.03 {+-} 4.48%, and 2.24 {+-} 3.11%, respectively (P = 0.014, 0.003, 0.053, and 0.046, respectively). The 3-phase radiotherapy protocol showed improved dosimetric results to the critical structures while keeping satisfactory target dose coverage, which demonstrated the advantages of ART in helical tomotherapy of NPC.

• OSTI ID: 22130386
• Journal Information: Medical Dosimetry, Journal Name: Medical Dosimetry Journal Issue: 1 Vol. 37; ISSN 0958-3947
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
CARCINOMAS
CAT SCANNING
CT-GUIDED RADIOTHERAPY
DOSIMETRY
HEAD
HEALTH HAZARDS
NECK
PATIENTS
PITUITARY GLAND
RADIATION DOSES
SPINAL CORD