Friday, October 6, 2023

Analyzing dose parameters of radiation therapy treatment planning and estimation of their influence on secondary cancer risks

The Georgian Health Physics Association (GHPA) hosted an online technical meeting on October 6, 2023, featuring Maia Topeshashvili, MS, Chief Medical Physicist from the Radiation Oncology Department at Todua Clinic.

The meeting focused on the vital topic of estimating secondary cancer risk following breast cancer radiotherapy, employing organ equivalent dose (OED) concepts. Maia Topeshashvili's presentation provided crucial insights into this subject, with detailed findings from a study involving multiple breast cancer patients.

For comprehensive details on the study's results and implications, please refer to the abstract and the full presentation YouTube recording below.

Maia Topeshashvili, Medical Physicist from Todua Clinic presenting to GHPA

Meeting Information

Maia Topeshashvili, MS
Chief Medical Physicist
Radiation Oncology Department
"Todua Clinic"

When: Friday, October 6, 2023 at 6:00 PM
Where: Online meeting


Breast Cancer is no longer considered a death sentence and the number of patients receiving radiotherapy is increasing every year. Advancements in RT technology allow more accurate and accumulated delivery of radiation significantly reducing the risk of side effects. The use of these techniques has led to better clinical outcomes and significantly increased long-term survival rates. Therefore, secondary cancer risk after breast conserving therapy is becoming more important. In this study, we estimate the risks of developing a solid second cancer after radiotherapy of breast cancer using the concept of organ equivalent dose (OED). 

Eight breast cancer patients were retrospectively selected for this study. Three-dimensional conformal radiotherapy (3DCRT), intensity modulated radiotherapy (IMRT), and volumetric modulated arc therapy (VMAT) were planned to deliver a prescribed dose. Differential dose volume histograms (dDVHs) were created and the OEDs calculated. Secondary cancer risks of ipsilateral, contralateral lung and thyroid gland were estimated using linear, linear-exponential and plateau models. 

The highest interest of our study was the evaluation of secondary cancer risk for the organs at risk (OAR), which are located far from the treatment region and are very sensitive to radiation exposure. Our results showed very high secondary cancer excess absolute risk (EAR) values for IMRT and VMAT compared with 3DCRT. It has to be noted, that a significant reduction of the EARs for the contralateral lung, ipsilateral lung and thyroid gland was observed in all dose–response models.

Keywords: 3DCRT (3D Conformal Radiotherapy), IMRT (Intensity modulated Radiotherapy), VMAT (Volumetric modulated Radiotherapy), secondary cancer risk, Organ equivalent dose (OED)

CiteTopeshashvili M Analyzing dose parameters of radiation therapy treatment planning and estimation of their influence on secondary cancer risks. GHPA Technical Meeting, Tbilisi, Georgia, 6 Oct. 2023. Available at:

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