Abstract 877P
Background
Although intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and tomotherapy (TOMO) are broadly applied in nasopharyngeal carcinoma (NPC), the best technique remains unclear. Therefore, this research was conducted to address this issue.
Methods
Radiation plans for forty NPC cases were replanned by IMRT, VMAT and TOMO according to the latest international guidelines on dose prioritization and acceptance criteria; the dosimetric parameters of planning target volumes (PTVs) and organs at risk (OARs) were compared among the three techniques. The Friedman M test in SPSS software was applied to assess significant differences.
Results
The median PGTVnx coverage of IMRT was the lowest (93%, P <0.05) for all T categories. VMAT was comparable to TOMO, and both satisfied the prescribed requirement. IMRT resulted in a relatively high dose in the majority of OARs and for parameters of low-dose radiation volume. Interestingly, subgroup analysis showed that the median PTV coverage of the three techniques was no less than 96% in the early T stage. The PTV conformity index (CI) was the worst for IMRT (P <0.05). Compared to TOMO, VMAT showed a strong ability to protect eyesight and decrease low-dose radiation volumes. In the advanced T stage subgroup, TOMO numerically achieved the highest median PGTVnx coverage volume compared with VMAT and IMRT (93.61%, 91% and 90%, respectively). TOMO was better than VMAT in sparing the brain stem, spinal cord and temporal lobes (all P <0.05). However, the median V10, V15, V20 values and V25 were significantly higher for TOMO than for VMAT (all P <0.01).
Conclusions
In the early T stage, VMAT provides a similar dose coverage and OARs protection compared to IMRT, and there are no obvious advantages to choosing TOMO for NPC patients in the early T stage. TOMO is recommended for patients in the advanced T stage due to the largest dose coverage of PGTVnx and the best protecting of the brain stem and spinal cord. Additionally, more randomized clinical trials are needed for further clarification.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
People’s Government of Yunnan Province, China; The National Natural Science Foundation of China.
Disclosure
All authors have declared no conflicts of interest.