Gastric and/or Oesophageal Cancer - Methodology

This document provides background information on the clinical and technical logic applied to the set-up of the Gastric and/or Oesophageal dashboard, and includes:  

• How the market and patient cohorts have been defined 
• Inclusion and exclusion criteria including clinical or technical reasoning
• Any clinical and technical assumptions that have been made, limitations and potential implications 

Familiarising yourself with the logic that has been applied prior to exploring your dashboard will enable more relevant and accurate insights and consistency in interpretation of the data across your business.  

What data is used for my dashboard?

This dashboard has been set up using the PBS 10% dataset. More information about this dataset can be found here.

How has the Gastric and/or Oesophageal market been defined?

Patient Cohort Selection Rule

Only patients with an authority code for gastric cancer, oesophageal cancer or gastro-oesophageal junction cancer have been included in this dashboard. These authority codes are predominantly restricted to advanced or stage IV (metastatic) gastric and oesophageal cancers. As a result, the gastric and oesophageal cancer market is predominantly advanced or metastatic.

Medications Included

Based on PBS authority codes and the patient cohort selection rules, the dashboard contains data relating to the following medicines:

Exclusions and rationale

Patients prescribed only chemotherapies that do not have a gastric cancer, oesophageal cancer or gastro-oesophageal junction cancer authority code have been excluded from the dashboard. It is assumed that these patients are being treated for a different indication.

• Calcium folinate, capecitabine, carboplatin, cisplatin, docetaxel, epirubicin, fluorouracil, irinotecan and oxaliplatin are currently unrestricted chemotherapies on the PBS. As a result, there is an absence of adequate data to directly verify the supply of these chemotherapies for gastric and/or oesophageal cancer. Patients who have taken these chemotherapies must follow the cohort selection rules to ensure gastric and/or oesophageal patients are captured correctly.
• Trifluridine + tipiracil is currently indicated for gastric and/or oesophageal cancer and colorectal cancer. However, the PBS item codes were previously shared across the two therapeutic areas making it impossible to differentiate between the two indications using PBS codes alone. Patients who have taken trifluridine + tipiracil must follow the cohort selection rules to ensure gastric and/or oesophageal patients are captured correctly.

Drugs that have been discontinued more than five years ago have been excluded from the dashboard. 

What rules and assumptions have been applied to the dashboard/data?

All data sources have some inherent limitations. Prospection applies advanced analytic techniques to overcome some of these limitations and to help improve the quality of data and interpretation. 

HER-2

Trastuzumab is restricted to treatment of metastatic (Stage IV) HER2 positive adenocarcinoma of the stomach or gastro-oesophageal junction. As a result, patients who have purchased at least one script of Trastuzumab are deemed to be HER-2 positive.

Nivolumab in combination with chemotherapy is restricted to the treatment HER2 negative advanced or metastatic gastric or gastro-oesophageal junction or oesophageal adenocarcinoma. As a result, patients who have taken Nivolumab in regimen with chemotherapy are deemed to be HER-2 negative.

Maintenance

Trastuzumab is restricted to treatment in combination with chemotherapies or as maintenance treatment. Maintenance treatment is taken for cancer recurrence prevention after primary treatment. Here it involves taking trastuzumab as monotherapy after the completion of trastuzumab and chemotherapy. 

Regimens

PBS data does not provide clinical details indicating whether a patient is taking drugs in combination, therefore regimens are inferred algorithmically.  A regimen occurs when the period of continuous prescription overlaps between two or more agents. The gastric and/or oesophageal cancer dashboard includes regimens that are commonly used together as part of a treatment protocol in Australia that are listed on the PBS.  

Below is the list of regimens available in the gastric and/or oesophageal cancer dashboard: