A Standardized Nomenclature System for Head and Neck (H&N) IMRT Contouring, Planning and Quality Assurance

Abstract

A standardized system of H&N structure nomenclature, contouring and planning terminology was implemented in Sept. 2004 to facilitate 1) interdisciplinary communication 2) planning quality assurance review 3) the automation of planning tasks and 4) audit of outcomes. In Nov. 2006, the system was expanded to include more intensity modulated radiation therapy (IMRT)-specific planning terminology. An audit was conducted to evaluate physician compliance to our nomenclature system (NS) and to identify potential improvements to the NS. The NS conforms to ICRU 50/62 and Consensus Guidelines terminology for neck nodal levels. The NS is applicable to all H&N sites and presentations using a consistent alpha-numeric scripted language permitting unequivocal designation of radiation objects necessary for the deilvery of a very large academic H&N IMRT program. Integral to this system is the delineation of separate primary site and neck target volumes. There are guidelines to handle separate, multiple or combined targets. NS terminology for normal structures, gross disease and target volumes is unique, brief, consistent and descriptive. For patients who have undergone surgery or chemotherapy, there may be no gross tumor objects and these tumor sites may be considered high-risk. Currently, there is no ICRU terminology for this principle. Terminology was developed to enable physicians to contour these high-risk regions. Seven H&N radiation oncologists are responsible for primary, gross nodal, clinical target volume (CTV) and most organ at risk (OR) contours. Planning target volumes (PTVs), planning organ at risk volumes (PRVs) and other planning volumes are planner-generated. Physician-generated contours for all H&N patients starting radiotherapy from Dec. 1, 2006 to Feb. 28, 2007 were audited. Terminology that was not consistent with NS standards and principles was considered a deviation. Terminology that was not addressed in the NS was categorized as non-NS. 132 patients (pharynx, larynx, oral cavity, nasal cavity/paranasal sinus, unknown primary, complex skin and sarcoma/benign tumors) treated with curative or palliative intent were included in this audit. In total, 2490 (397 gross tumor or high-risk, 625 CTV, 1283 OR, 131 reference and 54 non-NS) volumes were physician-generated. Deviations were found in 15/397 (3.8%) gross tumor/high-risk volumes, 28/625 (4.5%) CTVs and 35/1283 (2.7%) ORs. Of 273 gross nodal contours, 8 (2.9%) were assigned to the wrong nodal level in 5 patients. Deviations for gross or high-risk (primary/nodal) volumes, CTVs and ORs were found in 12/132 (9.1%), 18/132 (13.6%) and 19/132 (14.4%) patients respectively. No deviations resulted in violation of ICRU principles. Review of deviations and non-NS terminology identified the need to clarify or expand OR, bolus placement and post-operative nomenclature. A standardized H&N IMRT nomenclature system has been successfully adopted by radiation oncologists in a large academic centre. This system is applicable to any clinical environment.