International Consensus Guidelines on the Delineation of Radiation Therapy Target Volumes for Nasopharyngeal Carcinoma After Induction Chemotherapy Using a 2-Round Modified Delphi Survey

Abstract

Purpose: Induction chemotherapy (ICT), a new standard in the management of locally advanced nasopharyngeal carcinoma (NPC), is increasingly used in endemic regions. Radiation therapy (RT) target volume delineation protocols and dose level prescriptions vary significantly in the literature. High-level evidence to support a particular approach is currently lacking. We developed an international consensus guideline toward harmonizing practices based on a literature review and expert opinion.

Methods and materials: The study entailed the following: consensus scope definition by focus group discussion (FGD); evidence gap identification by a scoping review of guidelines and literature reviews; evidence review and synthesis by a systematic review of experimental and observational studies and drafting of consensus statements by FGD; and consensus voting by modified Delphi process and FGD. The task force consisted of radiation oncologists from intermediate- and high-endemicity regions with expertise in treating NPC, evidence review, and consensus guideline development. The consensus panel consisted of relevant specialists from intermediate- and high-endemicity regions or with expertise in treating NPC. A modified e-Delphi method was used.

Results: Four clinical situations after ICT for patients with NPC were selected for the consensus questions: optimal timing of chemoradiation; optimal imaging modalities for simulation and target volume delineation; optimal dose and fractionation; and RT target volume delineation. The consensus panel consisted of radiation oncologists (12), clinical oncologists (4), radiologists (3), a nuclear medicine specialist, medical physicists (2), and dosimetrists (2). The consensus guidelines were formulated after 2 rounds of Delphi voting and FGD; iterative revisions were made based on 2 rounds of internal review. The guidelines were subjected to external review and open commentary; further revisions were made if the consensus vote was not invalidated.

Conclusions: An international consensus guideline on delineating RT target volumes and corresponding dose levels in post-ICT NPC, as well as timing and modalities for imaging, was developed to help harmonize practices and enhance the comparability of interpretations of reported outcomes.