Sparing Sensitive Organs from Radiation Damage to Reduce Side Effects

A new way to plan radiotherapy could help shape treatment away from sensitive organs near tumors 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 tumors to kill cancer cells while sparing healthy tissue.

Doctors plan treatment carefully to achieve this based on patient scans, irradiating an area around a tumor 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 tumor 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 tumors, 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 tumors while also exposing these organs to less radiation than plans where no adjustments were made.

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 tumor 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 tumor. We demonstrated our technique to plan radiotherapy treatment for prostate cancer, but it could easily be adapted to other forms of the disease.”

This article has been republished from materials provided by the Institute of Cancer Research. Note: material may have been edited for length and content. For further information, please contact the cited source.

Reference: H S Tsang, et al. Novel adaptive beam-dependent margins for additional OAR sparing. Physics in Medicine & Biology (2018) DOI: https://doi.org/10.1088/1361-6560/aae658