What's in a Name?

Radiation Oncology

What’s in a Name?

While a rose by any other name would smell as sweet, if we all agree to call cow manure a rose, that would not make it smell any better. In order to communicate clearly about radiation treatments for patients we need to agree on exact definitions and words. There is significant diversity in how we assign names to target structures, organ-at-risk (OARs), and other treatment planning parameters like dose-volume histogram (DVH) terms. These inconsistencies exist within individuals’ practice, within our departments and almost certainly between departments.

In Australia and New Zealand, we can take advantage of the best of international expertise and experience and adapt it to our practice. In 2014, the American Association of Physicists in Medicine (AAPM) assigned a multidisciplinary group the considerable task of standardising structure names, nomenclature for dosimetric data and templates for clinical trial groups. The resulting report, published in 2018 (1) aims to point us in the right direction.

Standardisation has many advantages. Standardising how we name our planning terms can result in improved workflow, more efficient peer review and facilitate research when it comes to transferring treatment-related data between institutions.

In the short term, some proposed benefits are a faster, more systematic plan review process. With a standardised approach, scripting also becomes easier and we will be able to take advantage of automated processes in treatment planning systems.

Treatment protocols can be followed more closely and standardised naming will facilitate clinical improvement projects. In the longer term, a universal standardised approach in nomenclature can help with the emerging fields of Big Data and Machine Learning in radiation oncology. (2,3)

The report benefited from a diverse group of stakeholders including endusers of treatment planning software as well as vendors. The AAPM Task Group 263 thoroughly evaluated current practices across the US and distilled the most common practices and then made recommendations regarding the nomenclature of target volumes, nontarget volumes and DVH metrics.

Target structures

The International Commission on Radiation Terms and Measurements (ICRU) terms of GTV, CTV, PTV and ITV are reinforced, with the allowance of suffix classifiers as necessary—for example primary versus nodal volume annotated by lower case “p” and “n” respectively.

When specifying dose as part of the target volume name, it is recommended to use relative dose (PTV_High) rather than absolute dose.

Where absolute dose is absolutely necessary to specify, the authors state it ‘should be’ in cGy (PTV_5040)— largely because this is so common in the USA—however acknowledge that “[f]or clinics that currently use Gy for prescriptions, then the physical doses in Gy should be communicated explicitly with the addition of ‘Gy’ as a suffix” (e.g. PTV_50.4Gy).

Other specifiers such as number of fractions, cropping from other external contours and custom text are allowable also.

Non-target structures

A review of all recommendations for non-target structures is beyond the scope of this article, but some examples include using 16 characters or fewer (which is compatible with nearly all treatment planning systems), using unique names independent of capitalisation (Lung_L is the same as LUNG_L), and using underscore (“_”) instead of spaces.

DVH and dose constraints

The report recommends providing exact data on what is measured and including standardised input parameters and units used for dose and volume. This would allow for greater use of automated processes and automated calculations.

Colour specification

There is large variation in specification of preferred colours for target volumes. One of the only tenets that seems consistent across ROs in my department is the orange PTV contour, often presented in Pinnacle or Raystation in a colour wash with a solid outline. The report acknowledges the difficulties in proposing a uniform colour standard, including issues like background colour of the CT dataset, the colour of overlapping isodose lines in plan evaluation and even the fact that up to 10 per cent of the population may be colour-blind! Any RO or trainee who has contoured using a yellow brush on bone knows this predicament. However, proposed benefits of a standardised colour scheme include ease of peer review and plan interpretation. Although desirable, the report does not make specific recommendations, as currently it is not necessary to facilitate the transfer of data between institutions, instead making the recommendation that institutions may implement their own rules for the use of colour.

Implementation

“Change is hard. Implementing the new standards in the clinic requires addressing learning curves, implications for existing documentation, additional work for staff, process changes, etc. It is important to know that new recommendations can be successfully implemented in clinical settings.” AAPM Task Group 263, 2018

The group recognises that their recommendations cannot be adopted overnight and provides some practical suggestions regarding staged implementation. They have tried to make these recommendations as wide-reaching and applicable as possible to accommodate most treatment planning software systems and to be used alongside local protocols that are already in place and often times engrained in practice.

Summary

A strength of this work is the considerable buy-in involved from vendors, physicists and physicians in a collaborative effort. It is not only comprehensive, but also practical and adaptable to fit the workflow of modern radiation oncology departments regardless of the treatment planning software being used. This report provides a guiding light in order to standardise nomenclature across multiple facets of the radiation oncology planning process. The improvements can be seen in both intra- and interdepartmental communication. Australian radiation oncology departments should strive to adopt a suitable approach to meet their needs. We also have the benefit of several multi-site collaborative clinical trials groups in Australia that could no doubt benefit from a smooth transfer of data.

It may now be a timely opportunity for the Faculty to spearhead a project assessing the nomenclature practices of radiation oncology departments, and making sure what we all call a rose doesn’t smell like ‘cow manure’. This could be done with a view to launching a tripartite (clinicians, RTs and medical physicists) task force to lay the groundwork for standardised nomenclature in Australia. For the Twitter users among us, the task group have set up an account

Follow @AAPM_TG263U1 on Twitter to receive regular tips in implementing AAPM TG263 in your practice!

Dr Adam Byrne

Radiation Oncology Trainee SA/NT Training Network

Quality Improvement Committee Trainee Representative 2021

References 1. Standardizing Nomenclatures in Radiation Oncology The Report of AAPM Task Group 263. 2018;

2. Benedict SH, El Naqa I, Klein EE. Introduction to Big Data in Radiation Oncology: Exploring Opportunities for Research, Quality Assessment, and Clinical Care. Int J Radiat Oncol Biol Phys. 2016 Jul 1;95(3):871–2.

3. Feng M, Valdes G, Dixit N, Solberg TD. Machine learning in radiation oncology: Opportunities, requirements, and needs. Front Oncol. 2018;