Estimating Incidental Radiation Doses From Cancer Treatments
Researchers find ways to improve estimates for collateral radiation damage during radiotherapy.
Modern radiotherapy treats cancer by delivering a focused radiation beam to tumors; however, this invariably exposes other parts of the body to unwanted radiation. The relatively low doses that reach away from the primary targets are called out-of-field doses and are generally difficult to predict accurately.
The success of modern radiotherapy in treating cancer is perhaps a double-edged sword. The lengthened lifetimes of patients now allow more time for radiation-induced health complications to emerge, such as secondary cancer and cardiac toxicity. It can have potential significance for estimating the long-term risks of radiation therapy, especially among populations such as pediatric patients or patients who are pregnant.
To estimate long-term radiation-related risks, it is necessary to accurately quantify the relatively small out-of-field radiation doses patients receive during treatments. In radiation therapy, computer software can compute the total expected dose of radiation reaching the patients’ tissues. However, calculations of out-of-field doses may be inaccurate.
Recently, researchers compared calculated and measured out-of-field doses for patients undergoing radiation therapy for breast cancer. They compared out-of-field doses calculated by three commercial treatment planning system algorithms commonly used in clinical practice to thermoluminescent dosimeter measurements performed in 11 patients. The results were published in the journal Physics and Imaging in Radiation Oncology.
The researchers found that the accuracy of the calculated doses varied among the three algorithms. They were able to improve the accuracy of dose calculations by applying a correction for leakage radiation. The researchers say while the use of such corrections is feasible and could help improve estimated out-of-field radiation doses, it would likely require experimental verification in each case, as the value of the correction probably varies depending on the design of the radiation equipment.