Image: Micrograph of seminoma testes from a testicular germ cell tumour.
A new way to plan radiotherapy could help shape treatment away from sensitive organs near tumours to reduce side-effects, a new study shows.
The technique has been developed by physicists at The Institute of Cancer Research and our partner hospital, The Royal Marsden NHS Foundation Trust, and involves using complex mathematical formulae to spare sensitive organs from radiation damage.
Although radiotherapy cures many cancers, side-effects can occur months or even years after treatment and can significantly affect a patient’s quality of life.
Radiotherapy treatment attempts to deliver as high a dose of radiation as possible to tumours to kill cancer cells while sparing healthy tissue.
Doctors plan treatment carefully to achieve this based on patient scans, irradiating an area around a tumour to make sure it is hit by the radiation beam.
However, current plans do not account for the presence of organs close to the beam’s path.
Changing the shape of targeted therapy
For diseases like prostate cancer, nearby organs such as the bowel and rectum are particularly sensitive to radiation, so designing radiotherapy treatment margins that avoid them while still treating the whole tumour could lead to fewer side effects and better treatment overall.
The new technique, details of which are published in the journal Physics in Medicine & Biology, uses a concept called ‘adaptive margins’, which factors in nearby organs when planning the shape of radiotherapy treatment.
For the study, each beam of radiation was mapped to measure the cumulative exposure of tissue around tumours, before accounting for the position of sensitive organs nearby to adjust the margins used in treatment.
ICR researchers tested their system using data from five patients with prostate cancer, producing radiotherapy plans adjusted for the position of the bladder and the rectum.
They found their plans delivered doses of radiation to tumours while also exposing these organs to less radiation than plans where no adjustments were made.
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Increasing patient safety
Study leader Professor Uwe Oelfke, Head of the Joint Department of Physics at the ICR and The Royal Marsden, said:
“Radiotherapy is a very effective treatment for cancer, but the damaging effect of radiation on healthy tissue can lead to challenging side-effects that can affect a patient’s quality of life. Treatment margins are necessary to ensure the whole tumour is targeted, but a safe reduction of these margins is key to further improving outcomes for patients.
Henry Tsang the first author of the paper adds: “Our study shows adaptive margins that factor in the presence of nearby organs reduces their exposure to damaging radiation, while still treating the tumour. We demonstrated our technique to plan radiotherapy treatment for prostate cancer, but it could easily be adapted to other forms of the disease.”
The study was supported by Cancer Research UK and the NIHR Biomedical Research Centre at The Royal Marsden and the ICR.