HL7® FHIR® Te Aho o Te Kahu, Cancer Control Agency Implementation Guide
0.1.0 - CI Build

HL7® FHIR® Te Aho o Te Kahu, Cancer Control Agency Implementation Guide, published by Te Aho o Te Kahu, Cancer Control Agency. This guide is not an authorized publication; it is the continuous build for version 0.1.0 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7NZ/cca/ and changes regularly. See the Directory of published versions

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Official URL: http://hl7.org.nz/fhir/ig/cca/ImplementationGuide/hl7.org.nz.fhir.ig.cca | Version: 0.1.0
Active as of 2026-05-21 | Computable Name: CcaImplementationGuide

# Te Aho o Te Kahu, Cancer Control Agency Implementation Guide

### Background

This Implementation Guide describes the representaton of cancer treatment regimens (primarily chemotherapy created by the Cancer Control Agency). A regimen describes the treatment for a particular type of cancer and consists of a variable number of cycles, with each cycle defining one or more medication administrations on specific days within that cycle.

The guide defines profiles on PlanDefinition and ActivityDefinition resource types.

These are complex resource types, and have been significantly constrained for this usage. In particular, the 'action' element of the PlanDefinion resource is used in a specific manner. It has 2 levels of nesting.

In most cases the top level action represents a cycle and contains information like the cycle description, length, repeats (if any) and so forth. Each cycle contains any number of sub-actions representing the individual actions within that cycle - generally a medication administration (but can also be a procedure - see notes)

For example, a regimen that had 2 cycles, each of which defined the administration of 2 medications would be structured as folllows:

- action: first cycle
  - sub-action: drug 1
  - sub-action: drug 2
- action: second cycle
  - sub-action: drug 3
  - sub-action: drug 4

Details of each administration is found in the sub-action, which has an extension called timing-of-days that indicates the specific days within the cycle when the medication is to be administered. Note that the extension is actually a modifierExtension as it must be understood by the recipient for safe use of the resource. If it were to be ignored, then the wrong administration could be made.

The sub-action contains a reference to an ActivityDefinition resource which has the details of the medication (drug name, dose etc ).

There are however, regimens that provide a 'Treatment overview'. These are plan definitions that contain full regimens as children. These children or component regimens are contained resources. The treatment overview regimens do not contain activity definitions (cycles) only component regimens.

### Logical model

The Logical model describes the 'business level' or information model for the data in the guide. It helps to understand the information being represented in a simpler way than the profiles. It is does not represent the way the resource instances are structured or shared, but does have mappings to the profile in the tab at the top of the page (though these are intended to aid implementer understanding rather than being machine readible.)

### Examples

Examples are found at the top of each resource, and listed in the artifact index.

### Canonical Urls

Most of the resources defined in this guide (StructureDefinition, ValueSet, CodeSystem) have what is termed a 'canonical' url - an element with the name url. This functions as a globally unique identifier for these resources. At the time of writing, these url's should be considered provisional. New Zealand does not yet have a consistent way to define them, so they are subject to change. Hopefully this will be resolved before too much longer.

### Replacing regimens

It is common that regimens are deprecated over time and replaced by others. It is necessary to continue to make the deprecated guide available for historic purposes, but to indicate that it is no longer actively used. This is achieved by setting the status to "retired".

There is an extension - replaced-by that allows the deprecated plan to refer to the one that replaces it. Thus a user retrieving the deprecated plan can easily find the new one. This is a direct FHIR reference.

There is currently no reference from the new Plan back to the one that it has replaced.

### Contained resources

In this implementation, ActivityDefinition resources will be contained within the PlanDefinition and there uisn't a separate API for them (the only API is against PlanDefinition).

Component or child regimens will also be contained within the PlanDefinition. These are not available as separate resources

### Using this guide

- The Profiles tab contains the profiles defined by this IG
- The Extensions tab contains the Extension Definition resources defined by this IG
- Examples has the PlanDefinition examples
- Terminology has the ValueSets and CodeSystems
- Artifact Index has a list of all artifacts (including Examples, Profiles and Extensions)
- There will be an API tab to describe the external interface supported by the system. It is also feasible to 'bundle' the resources into a separate package for direct distribution to specific clients.