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Authors Li Y, Ou X, Shen C, Xu T, Li W, Hu C
Received 26 November 2017
Accepted for publication 20 March 2018
Published 7 May 2018 Volume 2018:11 Pages 2545—2555
DOI https://doi.org/10.2147/OTT.S158126
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Dr Justinn Cochran
Peer reviewer comments 5
Editor who approved publication: Dr Ingrid Espinoza
Background: To demonstrate the robustness of clinical target volume delineation for
nasopharyngeal carcinoma (NPC) patients, this study makes a detailed analysis
of the initial irradiated dose of the recurrent site and local failure patterns
after intensity-modulated radiation therapy (IMRT). Based on this analysis,
further improvement of delineation recommendations may be made in order to
improve the quality-of-life in NPC, without decreasing the local control and
survival rate.
Methods: In
total, 382 newly diagnosed non-metastatic NPC patients were retrospectively
enrolled, receiving elective neck irradiation to levels II, III, and VA. For
patients with local failure, the location and extent of local failures were
transferred to the pretreatment planning computed tomography (CT) for
dosimetric analysis. The dose of radiation received by GTVr (gross tumor volume
of recurrence) was calculated and analyzed with dose-volume histogram (DVH).
Failures were classified as: “in field” if 95% of GTVr was within the 95%
isodose, “marginal” if 20%–95% of GTVr was within the 95% isodose, or “outside”
if less than 20% of GTVr was inside the 95% isodose.
Results: With a median follow-up time of 61.3 months, 12
patients developed local recurrence (10 cases available). The 5-year overall
survival, local relapse–free survival, regional relapse–free survival, distant
metastasis failure–free survival, and disease–free survival were 87.8%, 95.2%,
99.1%, 93.3%, and 82.5%, respectively. Dose conformity with IMRT was excellent,
and the recurrence was mainly within 3 years after the first treatment. The
dosimetric analysis showed that seven failures were classified as “in-field”,
two failures as “marginal”, and only one failure as “out-field”. Most local
relapse sites located just the same site of primary tumor and most anatomic
sites were at low risk of concurrent bilateral tumor invasion.
Conclusions: IMRT with elective neck irradiation provides
excellent local control for NPC patients without cervical lymph node
metastasis. In-field failures are the main patterns for local recurrence, and
the radioresistant subvolumes within the gross tumor volume are needed to be
identified. This study proposed suggestions for reduction of target volume
during IMRT treatment for NPC patients.
Keywords: nasopharyngeal
carcinoma, intensity-modulated radiotherapy, patterns of local failure, reduction
of clinical target volume