Cancer patients benefitting from extra testing

9 May 2019

Additional testing is helping ensure that almost 1800 cancer patients per year are receiving safe and appropriate radiation doses during radiation oncology treatment.

Following a trial by Wellington Blood & Cancer Centre medical physicists and radiation therapists, CCDHB has become one of only a few DHBs to adopt in-vivo dosimetry (IVD) using an x-ray imager.

IVD measures the radiation exiting a patient’s body during therapy to calculate whether the radiation dose delivered was as expected.

“When we prepare a patient’s radiation treatment plan, we carry out a raft of checks and tests to ensure that the plan is safe,” said senior medical physicist and project physicist Rebecca Day.

“IVD is an extra test to ensure we spot a problem if there is one. Most patients have radiation over a number of appointments, so IVD during the first appointment enables us to spot and correct an error before treatment progresses too far.”

Project owner and chief medical physicist Lynne Greig explained that IVD is recommended by Australian and New Zealand radiation oncology practice standards, and other international guidelines, and the DHB saw the importance of implementing it for patients.

IVD is expected to detect few, or no, errors due to the many preceding checks. On the rare occasion where an error is detected, however, the impact can be significant.

“The impact of error depends on the site, or part of the body, you're treating,” said radiation therapist head of treatment Dean Paterson.

“Too little radiation means you’re less likely to eradicate or control a tumour, too much could result in an unexpected radiation-induced side-effect for the patient”

The project team is clear, however, that IVD will only detect errors on very rare occasions.

“It’s a safety net to catch errors that are rare and otherwise difficult to detect” said project owner and principal medical physicist Rob Louwe.

“When we run the test we don’t really expect to see anything – but it is an extra layer of safety and means patients can be reassured that we have a huge focus on providing quality and safe treatment.”

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