Room: Exhibit Hall
Purpose: There has been increasing interest in the risk of radiation induced secondary malignancies among radiation therapy patients. The purpose of this research is to adapt the epidemiological based model to evaluate the risks of secondary malignancies among radiation therapy cancer patients.
Methods: 7 prostate cases (Stage T1c toT3a) with different dose prescriptions under the care of same radiation oncologist, and treated with volumetric arc radiation therapy were selected for this research. The selection of organs at risk (OAR) was cross referenced with NIH SEER cancer registries publication â€œNew malignancies among cancer survivors reportâ€? (2006). The Excess Relative Risk (ERR) per sievert (Sv) radiation received of different OARs reported by BEIR VII report published by National Research Council (2006) was adapted for the risk of secondary malignancies assessment. Selected treatment plans were all created by the same dosimetrist and calculated with same set of beam and machine commissioning data using 2 different treatment planning systems with different dose calculation algorithms. Mean dose of each OAR was used for the risk assessment.
Results: Bladder, the most sensitive OAR based on this research, has the highest estimated ERR (ranged between 46.93 and 5.46). For Rectum, the estimated ERR range is between 6.85 and 0.95. For Colon, the estimated ERR range is between 1.26 and 0.05. The ERR estimation for the same OAR could vary up to 2.8 times based on the dose calculation results between the 2 chosen dose calculation algorithms.
Conclusion: This data suggests that prostate cancer patient receiving modern radiation therapy runs a significant increase of second cancer in the surrounding OARs. Further risk assessment for radiation therapy patients treated with different radiation treatment sites and treatment techniques under different radiation dose calculation platforms is suggested.