Individualization of Clinical Target Volume Delineation Based on Stepwise Spread of Nasopharyngeal Carcinoma: Outcome of More Than a Decade of Clinical Experience

Nina N. Sanford, Jackson Lau, Miranda B. Lam, Amy F. Juliano, Judith A. Adams, Saveli I. Goldberg, Hsiao Ming Lu, Yue C. Lu, Norbert J. Liebsch, Hugh D. Curtin, Annie W. Chan

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Abstract

Purpose: Radiation-related toxicity in nasopharyngeal carcinoma (NPC) is common. There are no well-established guidelines for clinical target volume (CTV) delineation with long-term follow-up. Current consensus continues to rely heavily on bony landmarks and fixed margins around the gross tumor volume (GTV), an approach used to define fields in the conventional 2- and 3-dimensional radiation therapy era. Methods and Materials: We retrospectively evaluated patients with newly diagnosed nonmetastatic NPC treated with definitive radiation therapy using a technique of CTV delineation based on individual tumor extent and the orderly stepwise pattern of tumor spread. Dosimetric comparisons were made between national protocol HN001 and our contouring strategies on a representative early- and advanced-stage NPC. The primary endpoints were patterns of failure and local control; secondary endpoints included regional control and survival, estimated using the Kaplan-Meier method. Results: Between 1999 and 2013, 73 patients (88% with stage 3-4 disease) were treated with median follow-up of 90 months for surviving patients. Median dose to GTV was 70 Gy. Four patients developed local recurrence and 1 patient developed regional recurrence. All locoregional recurrences occurred within the high-dose GTV. The 5-year local control, regional control, and overall survival was 94% (95% confidence interval [CI], 85%-98%), 99% (95% CI, 90%-100%), and 84% (95% CI, 73%-91%), respectively. Compared with HN001, our contouring strategy resulted in 62% and 36% reduction in CTV for T1 and T4 disease, respectively. In the T1 tumor, the reduction of doses to the contralateral parotid, optic nerve, and cochlea were 54%, 50%, 34% respectively. In the T4 case, there was a decrease of optic chiasm dose of 46% and contralateral optic nerve of 37%. There were 10 grade 3 toxicities. There was no grade 2 or higher xerostomia and no grade 4/5 toxicity. Conclusions: Our long-term experience with individualized CTV delineation based on stepwise patterns of spread results in excellent local control, with no recurrence outside the GTV.

Original languageEnglish (US)
Pages (from-to)654-668
Number of pages15
JournalInternational Journal of Radiation Oncology Biology Physics
Volume103
Issue number3
DOIs
StatePublished - Mar 1 2019
Externally publishedYes

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ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

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